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kernel-fxtec-pro1x/block/cfq-iosched.c
Vivek Goyal 70087dc38c blk-throttle: Use task_subsys_state() to determine a task's blkio_cgroup 
Currentlly we first map the task to cgroup and then cgroup to
blkio_cgroup. There is a more direct way to get to blkio_cgroup
from task using task_subsys_state(). Use that.

The real reason for the fix is that it also avoids a race in generic
cgroup code. During remount/umount rebind_subsystems() is called and
it can do following with and rcu protection.

cgrp->subsys[i] = NULL;

That means if somebody got hold of cgroup under rcu and then it tried
to do cgroup->subsys[] to get to blkio_cgroup, it would get NULL which
is wrong. I was running into this race condition with ltp running on a
upstream derived kernel and that lead to crash.

So ideally we should also fix cgroup generic code to wait for rcu
grace period before setting pointer to NULL. Li Zefan is not very keen
on introducing synchronize_wait() as he thinks it will slow
down moun/remount/umount operations.

So for the time being atleast fix the kernel crash by taking a more
direct route to blkio_cgroup.

One tester had reported a crash while running LTP on a derived kernel
and with this fix crash is no more seen while the test has been
running for over 6 days.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2011-05-16 15:24:08 +02:00

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/*
* CFQ, or complete fairness queueing, disk scheduler.
*
* Based on ideas from a previously unfinished io
* scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
*
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/elevator.h>
#include <linux/jiffies.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include <linux/blktrace_api.h>
#include "cfq.h"
/*
* tunables
*/
/* max queue in one round of service */
static const int cfq_quantum = 8;
static const int cfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
/* maximum backwards seek, in KiB */
static const int cfq_back_max = 16 * 1024;
/* penalty of a backwards seek */
static const int cfq_back_penalty = 2;
static const int cfq_slice_sync = HZ / 10;
static int cfq_slice_async = HZ / 25;
static const int cfq_slice_async_rq = 2;
static int cfq_slice_idle = HZ / 125;
static int cfq_group_idle = HZ / 125;
static const int cfq_target_latency = HZ * 3/10; /* 300 ms */
static const int cfq_hist_divisor = 4;
/*
* offset from end of service tree
*/
#define CFQ_IDLE_DELAY (HZ / 5)
/*
* below this threshold, we consider thinktime immediate
*/
#define CFQ_MIN_TT (2)
#define CFQ_SLICE_SCALE (5)
#define CFQ_HW_QUEUE_MIN (5)
#define CFQ_SERVICE_SHIFT 12
#define CFQQ_SEEK_THR (sector_t)(8 * 100)
#define CFQQ_CLOSE_THR (sector_t)(8 * 1024)
#define CFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
#define CFQQ_SEEKY(cfqq) (hweight32(cfqq->seek_history) > 32/8)
#define RQ_CIC(rq) \
((struct cfq_io_context *) (rq)->elevator_private[0])
#define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private[1])
#define RQ_CFQG(rq) (struct cfq_group *) ((rq)->elevator_private[2])
static struct kmem_cache *cfq_pool;
static struct kmem_cache *cfq_ioc_pool;
static DEFINE_PER_CPU(unsigned long, cfq_ioc_count);
static struct completion *ioc_gone;
static DEFINE_SPINLOCK(ioc_gone_lock);
static DEFINE_SPINLOCK(cic_index_lock);
static DEFINE_IDA(cic_index_ida);
#define CFQ_PRIO_LISTS IOPRIO_BE_NR
#define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
#define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
#define sample_valid(samples) ((samples) > 80)
#define rb_entry_cfqg(node) rb_entry((node), struct cfq_group, rb_node)
/*
* Most of our rbtree usage is for sorting with min extraction, so
* if we cache the leftmost node we don't have to walk down the tree
* to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
* move this into the elevator for the rq sorting as well.
*/
struct cfq_rb_root {
struct rb_root rb;
struct rb_node *left;
unsigned count;
unsigned total_weight;
u64 min_vdisktime;
};
#define CFQ_RB_ROOT (struct cfq_rb_root) { .rb = RB_ROOT, .left = NULL, \
.count = 0, .min_vdisktime = 0, }
/*
* Per process-grouping structure
*/
struct cfq_queue {
/* reference count */
int ref;
/* various state flags, see below */
unsigned int flags;
/* parent cfq_data */
struct cfq_data *cfqd;
/* service_tree member */
struct rb_node rb_node;
/* service_tree key */
unsigned long rb_key;
/* prio tree member */
struct rb_node p_node;
/* prio tree root we belong to, if any */
struct rb_root *p_root;
/* sorted list of pending requests */
struct rb_root sort_list;
/* if fifo isn't expired, next request to serve */
struct request *next_rq;
/* requests queued in sort_list */
int queued[2];
/* currently allocated requests */
int allocated[2];
/* fifo list of requests in sort_list */
struct list_head fifo;
/* time when queue got scheduled in to dispatch first request. */
unsigned long dispatch_start;
unsigned int allocated_slice;
unsigned int slice_dispatch;
/* time when first request from queue completed and slice started. */
unsigned long slice_start;
unsigned long slice_end;
long slice_resid;
/* pending metadata requests */
int meta_pending;
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
/* io prio of this group */
unsigned short ioprio, org_ioprio;
unsigned short ioprio_class, org_ioprio_class;
pid_t pid;
u32 seek_history;
sector_t last_request_pos;
struct cfq_rb_root *service_tree;
struct cfq_queue *new_cfqq;
struct cfq_group *cfqg;
/* Number of sectors dispatched from queue in single dispatch round */
unsigned long nr_sectors;
};
/*
* First index in the service_trees.
* IDLE is handled separately, so it has negative index
*/
enum wl_prio_t {
BE_WORKLOAD = 0,
RT_WORKLOAD = 1,
IDLE_WORKLOAD = 2,
CFQ_PRIO_NR,
};
/*
* Second index in the service_trees.
*/
enum wl_type_t {
ASYNC_WORKLOAD = 0,
SYNC_NOIDLE_WORKLOAD = 1,
SYNC_WORKLOAD = 2
};
/* This is per cgroup per device grouping structure */
struct cfq_group {
/* group service_tree member */
struct rb_node rb_node;
/* group service_tree key */
u64 vdisktime;
unsigned int weight;
unsigned int new_weight;
bool needs_update;
/* number of cfqq currently on this group */
int nr_cfqq;
/*
* Per group busy queus average. Useful for workload slice calc. We
* create the array for each prio class but at run time it is used
* only for RT and BE class and slot for IDLE class remains unused.
* This is primarily done to avoid confusion and a gcc warning.
*/
unsigned int busy_queues_avg[CFQ_PRIO_NR];
/*
* rr lists of queues with requests. We maintain service trees for
* RT and BE classes. These trees are subdivided in subclasses
* of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
* class there is no subclassification and all the cfq queues go on
* a single tree service_tree_idle.
* Counts are embedded in the cfq_rb_root
*/
struct cfq_rb_root service_trees[2][3];
struct cfq_rb_root service_tree_idle;
unsigned long saved_workload_slice;
enum wl_type_t saved_workload;
enum wl_prio_t saved_serving_prio;
struct blkio_group blkg;
#ifdef CONFIG_CFQ_GROUP_IOSCHED
struct hlist_node cfqd_node;
int ref;
#endif
/* number of requests that are on the dispatch list or inside driver */
int dispatched;
};
/*
* Per block device queue structure
*/
struct cfq_data {
struct request_queue *queue;
/* Root service tree for cfq_groups */
struct cfq_rb_root grp_service_tree;
struct cfq_group root_group;
/*
* The priority currently being served
*/
enum wl_prio_t serving_prio;
enum wl_type_t serving_type;
unsigned long workload_expires;
struct cfq_group *serving_group;
/*
* Each priority tree is sorted by next_request position. These
* trees are used when determining if two or more queues are
* interleaving requests (see cfq_close_cooperator).
*/
struct rb_root prio_trees[CFQ_PRIO_LISTS];
unsigned int busy_queues;
unsigned int busy_sync_queues;
int rq_in_driver;
int rq_in_flight[2];
/*
* queue-depth detection
*/
int rq_queued;
int hw_tag;
/*
* hw_tag can be
* -1 => indeterminate, (cfq will behave as if NCQ is present, to allow better detection)
* 1 => NCQ is present (hw_tag_est_depth is the estimated max depth)
* 0 => no NCQ
*/
int hw_tag_est_depth;
unsigned int hw_tag_samples;
/*
* idle window management
*/
struct timer_list idle_slice_timer;
struct work_struct unplug_work;
struct cfq_queue *active_queue;
struct cfq_io_context *active_cic;
/*
* async queue for each priority case
*/
struct cfq_queue *async_cfqq[2][IOPRIO_BE_NR];
struct cfq_queue *async_idle_cfqq;
sector_t last_position;
/*
* tunables, see top of file
*/
unsigned int cfq_quantum;
unsigned int cfq_fifo_expire[2];
unsigned int cfq_back_penalty;
unsigned int cfq_back_max;
unsigned int cfq_slice[2];
unsigned int cfq_slice_async_rq;
unsigned int cfq_slice_idle;
unsigned int cfq_group_idle;
unsigned int cfq_latency;
unsigned int cic_index;
struct list_head cic_list;
/*
* Fallback dummy cfqq for extreme OOM conditions
*/
struct cfq_queue oom_cfqq;
unsigned long last_delayed_sync;
/* List of cfq groups being managed on this device*/
struct hlist_head cfqg_list;
struct rcu_head rcu;
};
static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd);
static struct cfq_rb_root *service_tree_for(struct cfq_group *cfqg,
enum wl_prio_t prio,
enum wl_type_t type)
{
if (!cfqg)
return NULL;
if (prio == IDLE_WORKLOAD)
return &cfqg->service_tree_idle;
return &cfqg->service_trees[prio][type];
}
enum cfqq_state_flags {
CFQ_CFQQ_FLAG_on_rr = 0, /* on round-robin busy list */
CFQ_CFQQ_FLAG_wait_request, /* waiting for a request */
CFQ_CFQQ_FLAG_must_dispatch, /* must be allowed a dispatch */
CFQ_CFQQ_FLAG_must_alloc_slice, /* per-slice must_alloc flag */
CFQ_CFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
CFQ_CFQQ_FLAG_idle_window, /* slice idling enabled */
CFQ_CFQQ_FLAG_prio_changed, /* task priority has changed */
CFQ_CFQQ_FLAG_slice_new, /* no requests dispatched in slice */
CFQ_CFQQ_FLAG_sync, /* synchronous queue */
CFQ_CFQQ_FLAG_coop, /* cfqq is shared */
CFQ_CFQQ_FLAG_split_coop, /* shared cfqq will be splitted */
CFQ_CFQQ_FLAG_deep, /* sync cfqq experienced large depth */
CFQ_CFQQ_FLAG_wait_busy, /* Waiting for next request */
};
#define CFQ_CFQQ_FNS(name) \
static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
{ \
(cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
{ \
(cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
} \
static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
{ \
return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
}
CFQ_CFQQ_FNS(on_rr);
CFQ_CFQQ_FNS(wait_request);
CFQ_CFQQ_FNS(must_dispatch);
CFQ_CFQQ_FNS(must_alloc_slice);
CFQ_CFQQ_FNS(fifo_expire);
CFQ_CFQQ_FNS(idle_window);
CFQ_CFQQ_FNS(prio_changed);
CFQ_CFQQ_FNS(slice_new);
CFQ_CFQQ_FNS(sync);
CFQ_CFQQ_FNS(coop);
CFQ_CFQQ_FNS(split_coop);
CFQ_CFQQ_FNS(deep);
CFQ_CFQQ_FNS(wait_busy);
#undef CFQ_CFQQ_FNS
#ifdef CONFIG_CFQ_GROUP_IOSCHED
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq%d%c %s " fmt, (cfqq)->pid, \
cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
blkg_path(&(cfqq)->cfqg->blkg), ##args);
#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "%s " fmt, \
blkg_path(&(cfqg)->blkg), ##args); \
#else
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
#define cfq_log_cfqg(cfqd, cfqg, fmt, args...) do {} while (0);
#endif
#define cfq_log(cfqd, fmt, args...) \
blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
/* Traverses through cfq group service trees */
#define for_each_cfqg_st(cfqg, i, j, st) \
for (i = 0; i <= IDLE_WORKLOAD; i++) \
for (j = 0, st = i < IDLE_WORKLOAD ? &cfqg->service_trees[i][j]\
: &cfqg->service_tree_idle; \
(i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
(i == IDLE_WORKLOAD && j == 0); \
j++, st = i < IDLE_WORKLOAD ? \
&cfqg->service_trees[i][j]: NULL) \
static inline bool iops_mode(struct cfq_data *cfqd)
{
/*
* If we are not idling on queues and it is a NCQ drive, parallel
* execution of requests is on and measuring time is not possible
* in most of the cases until and unless we drive shallower queue
* depths and that becomes a performance bottleneck. In such cases
* switch to start providing fairness in terms of number of IOs.
*/
if (!cfqd->cfq_slice_idle && cfqd->hw_tag)
return true;
else
return false;
}
static inline enum wl_prio_t cfqq_prio(struct cfq_queue *cfqq)
{
if (cfq_class_idle(cfqq))
return IDLE_WORKLOAD;
if (cfq_class_rt(cfqq))
return RT_WORKLOAD;
return BE_WORKLOAD;
}
static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
{
if (!cfq_cfqq_sync(cfqq))
return ASYNC_WORKLOAD;
if (!cfq_cfqq_idle_window(cfqq))
return SYNC_NOIDLE_WORKLOAD;
return SYNC_WORKLOAD;
}
static inline int cfq_group_busy_queues_wl(enum wl_prio_t wl,
struct cfq_data *cfqd,
struct cfq_group *cfqg)
{
if (wl == IDLE_WORKLOAD)
return cfqg->service_tree_idle.count;
return cfqg->service_trees[wl][ASYNC_WORKLOAD].count
+ cfqg->service_trees[wl][SYNC_NOIDLE_WORKLOAD].count
+ cfqg->service_trees[wl][SYNC_WORKLOAD].count;
}
static inline int cfqg_busy_async_queues(struct cfq_data *cfqd,
struct cfq_group *cfqg)
{
return cfqg->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count
+ cfqg->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
}
static void cfq_dispatch_insert(struct request_queue *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *, bool,
struct io_context *, gfp_t);
static struct cfq_io_context *cfq_cic_lookup(struct cfq_data *,
struct io_context *);
static inline struct cfq_queue *cic_to_cfqq(struct cfq_io_context *cic,
bool is_sync)
{
return cic->cfqq[is_sync];
}
static inline void cic_set_cfqq(struct cfq_io_context *cic,
struct cfq_queue *cfqq, bool is_sync)
{
cic->cfqq[is_sync] = cfqq;
}
#define CIC_DEAD_KEY 1ul
#define CIC_DEAD_INDEX_SHIFT 1
static inline void *cfqd_dead_key(struct cfq_data *cfqd)
{
return (void *)(cfqd->cic_index << CIC_DEAD_INDEX_SHIFT | CIC_DEAD_KEY);
}
static inline struct cfq_data *cic_to_cfqd(struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic->key;
if (unlikely((unsigned long) cfqd & CIC_DEAD_KEY))
return NULL;
return cfqd;
}
/*
* We regard a request as SYNC, if it's either a read or has the SYNC bit
* set (in which case it could also be direct WRITE).
*/
static inline bool cfq_bio_sync(struct bio *bio)
{
return bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC);
}
/*
* scheduler run of queue, if there are requests pending and no one in the
* driver that will restart queueing
*/
static inline void cfq_schedule_dispatch(struct cfq_data *cfqd)
{
if (cfqd->busy_queues) {
cfq_log(cfqd, "schedule dispatch");
kblockd_schedule_work(cfqd->queue, &cfqd->unplug_work);
}
}
/*
* Scale schedule slice based on io priority. Use the sync time slice only
* if a queue is marked sync and has sync io queued. A sync queue with async
* io only, should not get full sync slice length.
*/
static inline int cfq_prio_slice(struct cfq_data *cfqd, bool sync,
unsigned short prio)
{
const int base_slice = cfqd->cfq_slice[sync];
WARN_ON(prio >= IOPRIO_BE_NR);
return base_slice + (base_slice/CFQ_SLICE_SCALE * (4 - prio));
}
static inline int
cfq_prio_to_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
return cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio);
}
static inline u64 cfq_scale_slice(unsigned long delta, struct cfq_group *cfqg)
{
u64 d = delta << CFQ_SERVICE_SHIFT;
d = d * BLKIO_WEIGHT_DEFAULT;
do_div(d, cfqg->weight);
return d;
}
static inline u64 max_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
s64 delta = (s64)(vdisktime - min_vdisktime);
if (delta > 0)
min_vdisktime = vdisktime;
return min_vdisktime;
}
static inline u64 min_vdisktime(u64 min_vdisktime, u64 vdisktime)
{
s64 delta = (s64)(vdisktime - min_vdisktime);
if (delta < 0)
min_vdisktime = vdisktime;
return min_vdisktime;
}
static void update_min_vdisktime(struct cfq_rb_root *st)
{
struct cfq_group *cfqg;
if (st->left) {
cfqg = rb_entry_cfqg(st->left);
st->min_vdisktime = max_vdisktime(st->min_vdisktime,
cfqg->vdisktime);
}
}
/*
* get averaged number of queues of RT/BE priority.
* average is updated, with a formula that gives more weight to higher numbers,
* to quickly follows sudden increases and decrease slowly
*/
static inline unsigned cfq_group_get_avg_queues(struct cfq_data *cfqd,
struct cfq_group *cfqg, bool rt)
{
unsigned min_q, max_q;
unsigned mult = cfq_hist_divisor - 1;
unsigned round = cfq_hist_divisor / 2;
unsigned busy = cfq_group_busy_queues_wl(rt, cfqd, cfqg);
min_q = min(cfqg->busy_queues_avg[rt], busy);
max_q = max(cfqg->busy_queues_avg[rt], busy);
cfqg->busy_queues_avg[rt] = (mult * max_q + min_q + round) /
cfq_hist_divisor;
return cfqg->busy_queues_avg[rt];
}
static inline unsigned
cfq_group_slice(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
return cfq_target_latency * cfqg->weight / st->total_weight;
}
static inline unsigned
cfq_scaled_cfqq_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
unsigned slice = cfq_prio_to_slice(cfqd, cfqq);
if (cfqd->cfq_latency) {
/*
* interested queues (we consider only the ones with the same
* priority class in the cfq group)
*/
unsigned iq = cfq_group_get_avg_queues(cfqd, cfqq->cfqg,
cfq_class_rt(cfqq));
unsigned sync_slice = cfqd->cfq_slice[1];
unsigned expect_latency = sync_slice * iq;
unsigned group_slice = cfq_group_slice(cfqd, cfqq->cfqg);
if (expect_latency > group_slice) {
unsigned base_low_slice = 2 * cfqd->cfq_slice_idle;
/* scale low_slice according to IO priority
* and sync vs async */
unsigned low_slice =
min(slice, base_low_slice * slice / sync_slice);
/* the adapted slice value is scaled to fit all iqs
* into the target latency */
slice = max(slice * group_slice / expect_latency,
low_slice);
}
}
return slice;
}
static inline void
cfq_set_prio_slice(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
unsigned slice = cfq_scaled_cfqq_slice(cfqd, cfqq);
cfqq->slice_start = jiffies;
cfqq->slice_end = jiffies + slice;
cfqq->allocated_slice = slice;
cfq_log_cfqq(cfqd, cfqq, "set_slice=%lu", cfqq->slice_end - jiffies);
}
/*
* We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
* isn't valid until the first request from the dispatch is activated
* and the slice time set.
*/
static inline bool cfq_slice_used(struct cfq_queue *cfqq)
{
if (cfq_cfqq_slice_new(cfqq))
return false;
if (time_before(jiffies, cfqq->slice_end))
return false;
return true;
}
/*
* Lifted from AS - choose which of rq1 and rq2 that is best served now.
* We choose the request that is closest to the head right now. Distance
* behind the head is penalized and only allowed to a certain extent.
*/
static struct request *
cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, sector_t last)
{
sector_t s1, s2, d1 = 0, d2 = 0;
unsigned long back_max;
#define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
#define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
unsigned wrap = 0; /* bit mask: requests behind the disk head? */
if (rq1 == NULL || rq1 == rq2)
return rq2;
if (rq2 == NULL)
return rq1;
if (rq_is_sync(rq1) && !rq_is_sync(rq2))
return rq1;
else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
return rq2;
if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
return rq1;
else if ((rq2->cmd_flags & REQ_META) &&
!(rq1->cmd_flags & REQ_META))
return rq2;
s1 = blk_rq_pos(rq1);
s2 = blk_rq_pos(rq2);
/*
* by definition, 1KiB is 2 sectors
*/
back_max = cfqd->cfq_back_max * 2;
/*
* Strict one way elevator _except_ in the case where we allow
* short backward seeks which are biased as twice the cost of a
* similar forward seek.
*/
if (s1 >= last)
d1 = s1 - last;
else if (s1 + back_max >= last)
d1 = (last - s1) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ1_WRAP;
if (s2 >= last)
d2 = s2 - last;
else if (s2 + back_max >= last)
d2 = (last - s2) * cfqd->cfq_back_penalty;
else
wrap |= CFQ_RQ2_WRAP;
/* Found required data */
/*
* By doing switch() on the bit mask "wrap" we avoid having to
* check two variables for all permutations: --> faster!
*/
switch (wrap) {
case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
if (d1 < d2)
return rq1;
else if (d2 < d1)
return rq2;
else {
if (s1 >= s2)
return rq1;
else
return rq2;
}
case CFQ_RQ2_WRAP:
return rq1;
case CFQ_RQ1_WRAP:
return rq2;
case (CFQ_RQ1_WRAP|CFQ_RQ2_WRAP): /* both rqs wrapped */
default:
/*
* Since both rqs are wrapped,
* start with the one that's further behind head
* (--> only *one* back seek required),
* since back seek takes more time than forward.
*/
if (s1 <= s2)
return rq1;
else
return rq2;
}
}
/*
* The below is leftmost cache rbtree addon
*/
static struct cfq_queue *cfq_rb_first(struct cfq_rb_root *root)
{
/* Service tree is empty */
if (!root->count)
return NULL;
if (!root->left)
root->left = rb_first(&root->rb);
if (root->left)
return rb_entry(root->left, struct cfq_queue, rb_node);
return NULL;
}
static struct cfq_group *cfq_rb_first_group(struct cfq_rb_root *root)
{
if (!root->left)
root->left = rb_first(&root->rb);
if (root->left)
return rb_entry_cfqg(root->left);
return NULL;
}
static void rb_erase_init(struct rb_node *n, struct rb_root *root)
{
rb_erase(n, root);
RB_CLEAR_NODE(n);
}
static void cfq_rb_erase(struct rb_node *n, struct cfq_rb_root *root)
{
if (root->left == n)
root->left = NULL;
rb_erase_init(n, &root->rb);
--root->count;
}
/*
* would be nice to take fifo expire time into account as well
*/
static struct request *
cfq_find_next_rq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *last)
{
struct rb_node *rbnext = rb_next(&last->rb_node);
struct rb_node *rbprev = rb_prev(&last->rb_node);
struct request *next = NULL, *prev = NULL;
BUG_ON(RB_EMPTY_NODE(&last->rb_node));
if (rbprev)
prev = rb_entry_rq(rbprev);
if (rbnext)
next = rb_entry_rq(rbnext);
else {
rbnext = rb_first(&cfqq->sort_list);
if (rbnext && rbnext != &last->rb_node)
next = rb_entry_rq(rbnext);
}
return cfq_choose_req(cfqd, next, prev, blk_rq_pos(last));
}
static unsigned long cfq_slice_offset(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
/*
* just an approximation, should be ok.
*/
return (cfqq->cfqg->nr_cfqq - 1) * (cfq_prio_slice(cfqd, 1, 0) -
cfq_prio_slice(cfqd, cfq_cfqq_sync(cfqq), cfqq->ioprio));
}
static inline s64
cfqg_key(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
return cfqg->vdisktime - st->min_vdisktime;
}
static void
__cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
struct rb_node **node = &st->rb.rb_node;
struct rb_node *parent = NULL;
struct cfq_group *__cfqg;
s64 key = cfqg_key(st, cfqg);
int left = 1;
while (*node != NULL) {
parent = *node;
__cfqg = rb_entry_cfqg(parent);
if (key < cfqg_key(st, __cfqg))
node = &parent->rb_left;
else {
node = &parent->rb_right;
left = 0;
}
}
if (left)
st->left = &cfqg->rb_node;
rb_link_node(&cfqg->rb_node, parent, node);
rb_insert_color(&cfqg->rb_node, &st->rb);
}
static void
cfq_update_group_weight(struct cfq_group *cfqg)
{
BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
if (cfqg->needs_update) {
cfqg->weight = cfqg->new_weight;
cfqg->needs_update = false;
}
}
static void
cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
cfq_update_group_weight(cfqg);
__cfq_group_service_tree_add(st, cfqg);
st->total_weight += cfqg->weight;
}
static void
cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
struct cfq_group *__cfqg;
struct rb_node *n;
cfqg->nr_cfqq++;
if (!RB_EMPTY_NODE(&cfqg->rb_node))
return;
/*
* Currently put the group at the end. Later implement something
* so that groups get lesser vtime based on their weights, so that
* if group does not loose all if it was not continuously backlogged.
*/
n = rb_last(&st->rb);
if (n) {
__cfqg = rb_entry_cfqg(n);
cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
} else
cfqg->vdisktime = st->min_vdisktime;
cfq_group_service_tree_add(st, cfqg);
}
static void
cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
{
st->total_weight -= cfqg->weight;
if (!RB_EMPTY_NODE(&cfqg->rb_node))
cfq_rb_erase(&cfqg->rb_node, st);
}
static void
cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
BUG_ON(cfqg->nr_cfqq < 1);
cfqg->nr_cfqq--;
/* If there are other cfq queues under this group, don't delete it */
if (cfqg->nr_cfqq)
return;
cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
cfq_group_service_tree_del(st, cfqg);
cfqg->saved_workload_slice = 0;
cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
}
static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq,
unsigned int *unaccounted_time)
{
unsigned int slice_used;
/*
* Queue got expired before even a single request completed or
* got expired immediately after first request completion.
*/
if (!cfqq->slice_start || cfqq->slice_start == jiffies) {
/*
* Also charge the seek time incurred to the group, otherwise
* if there are mutiple queues in the group, each can dispatch
* a single request on seeky media and cause lots of seek time
* and group will never know it.
*/
slice_used = max_t(unsigned, (jiffies - cfqq->dispatch_start),
1);
} else {
slice_used = jiffies - cfqq->slice_start;
if (slice_used > cfqq->allocated_slice) {
*unaccounted_time = slice_used - cfqq->allocated_slice;
slice_used = cfqq->allocated_slice;
}
if (time_after(cfqq->slice_start, cfqq->dispatch_start))
*unaccounted_time += cfqq->slice_start -
cfqq->dispatch_start;
}
return slice_used;
}
static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
struct cfq_queue *cfqq)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
unsigned int used_sl, charge, unaccounted_sl = 0;
int nr_sync = cfqg->nr_cfqq - cfqg_busy_async_queues(cfqd, cfqg)
- cfqg->service_tree_idle.count;
BUG_ON(nr_sync < 0);
used_sl = charge = cfq_cfqq_slice_usage(cfqq, &unaccounted_sl);
if (iops_mode(cfqd))
charge = cfqq->slice_dispatch;
else if (!cfq_cfqq_sync(cfqq) && !nr_sync)
charge = cfqq->allocated_slice;
/* Can't update vdisktime while group is on service tree */
cfq_group_service_tree_del(st, cfqg);
cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
/* If a new weight was requested, update now, off tree */
cfq_group_service_tree_add(st, cfqg);
/* This group is being expired. Save the context */
if (time_after(cfqd->workload_expires, jiffies)) {
cfqg->saved_workload_slice = cfqd->workload_expires
- jiffies;
cfqg->saved_workload = cfqd->serving_type;
cfqg->saved_serving_prio = cfqd->serving_prio;
} else
cfqg->saved_workload_slice = 0;
cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
st->min_vdisktime);
cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u disp=%u charge=%u iops=%u"
" sect=%u", used_sl, cfqq->slice_dispatch, charge,
iops_mode(cfqd), cfqq->nr_sectors);
cfq_blkiocg_update_timeslice_used(&cfqg->blkg, used_sl,
unaccounted_sl);
cfq_blkiocg_set_start_empty_time(&cfqg->blkg);
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
{
if (blkg)
return container_of(blkg, struct cfq_group, blkg);
return NULL;
}
void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
unsigned int weight)
{
struct cfq_group *cfqg = cfqg_of_blkg(blkg);
cfqg->new_weight = weight;
cfqg->needs_update = true;
}
static struct cfq_group * cfq_find_alloc_cfqg(struct cfq_data *cfqd,
struct blkio_cgroup *blkcg, int create)
{
struct cfq_group *cfqg = NULL;
void *key = cfqd;
int i, j;
struct cfq_rb_root *st;
struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
unsigned int major, minor;
cfqg = cfqg_of_blkg(blkiocg_lookup_group(blkcg, key));
if (cfqg && !cfqg->blkg.dev && bdi->dev && dev_name(bdi->dev)) {
sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
cfqg->blkg.dev = MKDEV(major, minor);
goto done;
}
if (cfqg || !create)
goto done;
cfqg = kzalloc_node(sizeof(*cfqg), GFP_ATOMIC, cfqd->queue->node);
if (!cfqg)
goto done;
for_each_cfqg_st(cfqg, i, j, st)
*st = CFQ_RB_ROOT;
RB_CLEAR_NODE(&cfqg->rb_node);
/*
* Take the initial reference that will be released on destroy
* This can be thought of a joint reference by cgroup and
* elevator which will be dropped by either elevator exit
* or cgroup deletion path depending on who is exiting first.
*/
cfqg->ref = 1;
/*
* Add group onto cgroup list. It might happen that bdi->dev is
* not initialized yet. Initialize this new group without major
* and minor info and this info will be filled in once a new thread
* comes for IO. See code above.
*/
if (bdi->dev) {
sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
MKDEV(major, minor));
} else
cfq_blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
0);
cfqg->weight = blkcg_get_weight(blkcg, cfqg->blkg.dev);
/* Add group on cfqd list */
hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
done:
return cfqg;
}
/*
* Search for the cfq group current task belongs to. If create = 1, then also
* create the cfq group if it does not exist. request_queue lock must be held.
*/
static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
{
struct blkio_cgroup *blkcg;
struct cfq_group *cfqg = NULL;
rcu_read_lock();
blkcg = task_blkio_cgroup(current);
cfqg = cfq_find_alloc_cfqg(cfqd, blkcg, create);
if (!cfqg && create)
cfqg = &cfqd->root_group;
rcu_read_unlock();
return cfqg;
}
static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
cfqg->ref++;
return cfqg;
}
static void cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg)
{
/* Currently, all async queues are mapped to root group */
if (!cfq_cfqq_sync(cfqq))
cfqg = &cfqq->cfqd->root_group;
cfqq->cfqg = cfqg;
/* cfqq reference on cfqg */
cfqq->cfqg->ref++;
}
static void cfq_put_cfqg(struct cfq_group *cfqg)
{
struct cfq_rb_root *st;
int i, j;
BUG_ON(cfqg->ref <= 0);
cfqg->ref--;
if (cfqg->ref)
return;
for_each_cfqg_st(cfqg, i, j, st)
BUG_ON(!RB_EMPTY_ROOT(&st->rb));
kfree(cfqg);
}
static void cfq_destroy_cfqg(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
/* Something wrong if we are trying to remove same group twice */
BUG_ON(hlist_unhashed(&cfqg->cfqd_node));
hlist_del_init(&cfqg->cfqd_node);
/*
* Put the reference taken at the time of creation so that when all
* queues are gone, group can be destroyed.
*/
cfq_put_cfqg(cfqg);
}
static void cfq_release_cfq_groups(struct cfq_data *cfqd)
{
struct hlist_node *pos, *n;
struct cfq_group *cfqg;
hlist_for_each_entry_safe(cfqg, pos, n, &cfqd->cfqg_list, cfqd_node) {
/*
* If cgroup removal path got to blk_group first and removed
* it from cgroup list, then it will take care of destroying
* cfqg also.
*/
if (!cfq_blkiocg_del_blkio_group(&cfqg->blkg))
cfq_destroy_cfqg(cfqd, cfqg);
}
}
/*
* Blk cgroup controller notification saying that blkio_group object is being
* delinked as associated cgroup object is going away. That also means that
* no new IO will come in this group. So get rid of this group as soon as
* any pending IO in the group is finished.
*
* This function is called under rcu_read_lock(). key is the rcu protected
* pointer. That means "key" is a valid cfq_data pointer as long as we are rcu
* read lock.
*
* "key" was fetched from blkio_group under blkio_cgroup->lock. That means
* it should not be NULL as even if elevator was exiting, cgroup deltion
* path got to it first.
*/
void cfq_unlink_blkio_group(void *key, struct blkio_group *blkg)
{
unsigned long flags;
struct cfq_data *cfqd = key;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
cfq_destroy_cfqg(cfqd, cfqg_of_blkg(blkg));
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
#else /* GROUP_IOSCHED */
static struct cfq_group *cfq_get_cfqg(struct cfq_data *cfqd, int create)
{
return &cfqd->root_group;
}
static inline struct cfq_group *cfq_ref_get_cfqg(struct cfq_group *cfqg)
{
return cfqg;
}
static inline void
cfq_link_cfqq_cfqg(struct cfq_queue *cfqq, struct cfq_group *cfqg) {
cfqq->cfqg = cfqg;
}
static void cfq_release_cfq_groups(struct cfq_data *cfqd) {}
static inline void cfq_put_cfqg(struct cfq_group *cfqg) {}
#endif /* GROUP_IOSCHED */
/*
* The cfqd->service_trees holds all pending cfq_queue's that have
* requests waiting to be processed. It is sorted in the order that
* we will service the queues.
*/
static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
bool add_front)
{
struct rb_node **p, *parent;
struct cfq_queue *__cfqq;
unsigned long rb_key;
struct cfq_rb_root *service_tree;
int left;
int new_cfqq = 1;
int group_changed = 0;
service_tree = service_tree_for(cfqq->cfqg, cfqq_prio(cfqq),
cfqq_type(cfqq));
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
parent = rb_last(&service_tree->rb);
if (parent && parent != &cfqq->rb_node) {
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
rb_key += __cfqq->rb_key;
} else
rb_key += jiffies;
} else if (!add_front) {
/*
* Get our rb key offset. Subtract any residual slice
* value carried from last service. A negative resid
* count indicates slice overrun, and this should position
* the next service time further away in the tree.
*/
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key -= cfqq->slice_resid;
cfqq->slice_resid = 0;
} else {
rb_key = -HZ;
__cfqq = cfq_rb_first(service_tree);
rb_key += __cfqq ? __cfqq->rb_key : jiffies;
}
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
new_cfqq = 0;
/*
* same position, nothing more to do
*/
if (rb_key == cfqq->rb_key &&
cfqq->service_tree == service_tree)
return;
cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
cfqq->service_tree = NULL;
}
left = 1;
parent = NULL;
cfqq->service_tree = service_tree;
p = &service_tree->rb.rb_node;
while (*p) {
struct rb_node **n;
parent = *p;
__cfqq = rb_entry(parent, struct cfq_queue, rb_node);
/*
* sort by key, that represents service time.
*/
if (time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
else {
n = &(*p)->rb_right;
left = 0;
}
p = n;
}
if (left)
service_tree->left = &cfqq->rb_node;
cfqq->rb_key = rb_key;
rb_link_node(&cfqq->rb_node, parent, p);
rb_insert_color(&cfqq->rb_node, &service_tree->rb);
service_tree->count++;
if ((add_front || !new_cfqq) && !group_changed)
return;
cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
}
static struct cfq_queue *
cfq_prio_tree_lookup(struct cfq_data *cfqd, struct rb_root *root,
sector_t sector, struct rb_node **ret_parent,
struct rb_node ***rb_link)
{
struct rb_node **p, *parent;
struct cfq_queue *cfqq = NULL;
parent = NULL;
p = &root->rb_node;
while (*p) {
struct rb_node **n;
parent = *p;
cfqq = rb_entry(parent, struct cfq_queue, p_node);
/*
* Sort strictly based on sector. Smallest to the left,
* largest to the right.
*/
if (sector > blk_rq_pos(cfqq->next_rq))
n = &(*p)->rb_right;
else if (sector < blk_rq_pos(cfqq->next_rq))
n = &(*p)->rb_left;
else
break;
p = n;
cfqq = NULL;
}
*ret_parent = parent;
if (rb_link)
*rb_link = p;
return cfqq;
}
static void cfq_prio_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct rb_node **p, *parent;
struct cfq_queue *__cfqq;
if (cfqq->p_root) {
rb_erase(&cfqq->p_node, cfqq->p_root);
cfqq->p_root = NULL;
}
if (cfq_class_idle(cfqq))
return;
if (!cfqq->next_rq)
return;
cfqq->p_root = &cfqd->prio_trees[cfqq->org_ioprio];
__cfqq = cfq_prio_tree_lookup(cfqd, cfqq->p_root,
blk_rq_pos(cfqq->next_rq), &parent, &p);
if (!__cfqq) {
rb_link_node(&cfqq->p_node, parent, p);
rb_insert_color(&cfqq->p_node, cfqq->p_root);
} else
cfqq->p_root = NULL;
}
/*
* Update cfqq's position in the service tree.
*/
static void cfq_resort_rr_list(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
/*
* Resorting requires the cfqq to be on the RR list already.
*/
if (cfq_cfqq_on_rr(cfqq)) {
cfq_service_tree_add(cfqd, cfqq, 0);
cfq_prio_tree_add(cfqd, cfqq);
}
}
/*
* add to busy list of queues for service, trying to be fair in ordering
* the pending list according to last request service
*/
static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
cfq_log_cfqq(cfqd, cfqq, "add_to_rr");
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
if (cfq_cfqq_sync(cfqq))
cfqd->busy_sync_queues++;
cfq_resort_rr_list(cfqd, cfqq);
}
/*
* Called when the cfqq no longer has requests pending, remove it from
* the service tree.
*/
static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
cfq_log_cfqq(cfqd, cfqq, "del_from_rr");
BUG_ON(!cfq_cfqq_on_rr(cfqq));
cfq_clear_cfqq_on_rr(cfqq);
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
cfq_rb_erase(&cfqq->rb_node, cfqq->service_tree);
cfqq->service_tree = NULL;
}
if (cfqq->p_root) {
rb_erase(&cfqq->p_node, cfqq->p_root);
cfqq->p_root = NULL;
}
cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
if (cfq_cfqq_sync(cfqq))
cfqd->busy_sync_queues--;
}
/*
* rb tree support functions
*/
static void cfq_del_rq_rb(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
const int sync = rq_is_sync(rq);
BUG_ON(!cfqq->queued[sync]);
cfqq->queued[sync]--;
elv_rb_del(&cfqq->sort_list, rq);
if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list)) {
/*
* Queue will be deleted from service tree when we actually
* expire it later. Right now just remove it from prio tree
* as it is empty.
*/
if (cfqq->p_root) {
rb_erase(&cfqq->p_node, cfqq->p_root);
cfqq->p_root = NULL;
}
}
}
static void cfq_add_rq_rb(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
struct cfq_data *cfqd = cfqq->cfqd;
struct request *__alias, *prev;
cfqq->queued[rq_is_sync(rq)]++;
/*
* looks a little odd, but the first insert might return an alias.
* if that happens, put the alias on the dispatch list
*/
while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
cfq_dispatch_insert(cfqd->queue, __alias);
if (!cfq_cfqq_on_rr(cfqq))
cfq_add_cfqq_rr(cfqd, cfqq);
/*
* check if this request is a better next-serve candidate
*/
prev = cfqq->next_rq;
cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq, cfqd->last_position);
/*
* adjust priority tree position, if ->next_rq changes
*/
if (prev != cfqq->next_rq)
cfq_prio_tree_add(cfqd, cfqq);
BUG_ON(!cfqq->next_rq);
}
static void cfq_reposition_rq_rb(struct cfq_queue *cfqq, struct request *rq)
{
elv_rb_del(&cfqq->sort_list, rq);
cfqq->queued[rq_is_sync(rq)]--;
cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
rq_data_dir(rq), rq_is_sync(rq));
cfq_add_rq_rb(rq);
cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
&cfqq->cfqd->serving_group->blkg, rq_data_dir(rq),
rq_is_sync(rq));
}
static struct request *
cfq_find_rq_fmerge(struct cfq_data *cfqd, struct bio *bio)
{
struct task_struct *tsk = current;
struct cfq_io_context *cic;
struct cfq_queue *cfqq;
cic = cfq_cic_lookup(cfqd, tsk->io_context);
if (!cic)
return NULL;
cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
if (cfqq) {
sector_t sector = bio->bi_sector + bio_sectors(bio);
return elv_rb_find(&cfqq->sort_list, sector);
}
return NULL;
}
static void cfq_activate_request(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
cfqd->rq_in_driver++;
cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "activate rq, drv=%d",
cfqd->rq_in_driver);
cfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
}
static void cfq_deactivate_request(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
WARN_ON(!cfqd->rq_in_driver);
cfqd->rq_in_driver--;
cfq_log_cfqq(cfqd, RQ_CFQQ(rq), "deactivate rq, drv=%d",
cfqd->rq_in_driver);
}
static void cfq_remove_request(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
if (cfqq->next_rq == rq)
cfqq->next_rq = cfq_find_next_rq(cfqq->cfqd, cfqq, rq);
list_del_init(&rq->queuelist);
cfq_del_rq_rb(rq);
cfqq->cfqd->rq_queued--;
cfq_blkiocg_update_io_remove_stats(&(RQ_CFQG(rq))->blkg,
rq_data_dir(rq), rq_is_sync(rq));
if (rq->cmd_flags & REQ_META) {
WARN_ON(!cfqq->meta_pending);
cfqq->meta_pending--;
}
}
static int cfq_merge(struct request_queue *q, struct request **req,
struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct request *__rq;
__rq = cfq_find_rq_fmerge(cfqd, bio);
if (__rq && elv_rq_merge_ok(__rq, bio)) {
*req = __rq;
return ELEVATOR_FRONT_MERGE;
}
return ELEVATOR_NO_MERGE;
}
static void cfq_merged_request(struct request_queue *q, struct request *req,
int type)
{
if (type == ELEVATOR_FRONT_MERGE) {
struct cfq_queue *cfqq = RQ_CFQQ(req);
cfq_reposition_rq_rb(cfqq, req);
}
}
static void cfq_bio_merged(struct request_queue *q, struct request *req,
struct bio *bio)
{
cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(req))->blkg,
bio_data_dir(bio), cfq_bio_sync(bio));
}
static void
cfq_merged_requests(struct request_queue *q, struct request *rq,
struct request *next)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
/*
* reposition in fifo if next is older than rq
*/
if (!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
time_before(rq_fifo_time(next), rq_fifo_time(rq))) {
list_move(&rq->queuelist, &next->queuelist);
rq_set_fifo_time(rq, rq_fifo_time(next));
}
if (cfqq->next_rq == next)
cfqq->next_rq = rq;
cfq_remove_request(next);
cfq_blkiocg_update_io_merged_stats(&(RQ_CFQG(rq))->blkg,
rq_data_dir(next), rq_is_sync(next));
}
static int cfq_allow_merge(struct request_queue *q, struct request *rq,
struct bio *bio)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_io_context *cic;
struct cfq_queue *cfqq;
/*
* Disallow merge of a sync bio into an async request.
*/
if (cfq_bio_sync(bio) && !rq_is_sync(rq))
return false;
/*
* Lookup the cfqq that this bio will be queued with. Allow
* merge only if rq is queued there.
*/
cic = cfq_cic_lookup(cfqd, current->io_context);
if (!cic)
return false;
cfqq = cic_to_cfqq(cic, cfq_bio_sync(bio));
return cfqq == RQ_CFQQ(rq);
}
static inline void cfq_del_timer(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
del_timer(&cfqd->idle_slice_timer);
cfq_blkiocg_update_idle_time_stats(&cfqq->cfqg->blkg);
}
static void __cfq_set_active_queue(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
if (cfqq) {
cfq_log_cfqq(cfqd, cfqq, "set_active wl_prio:%d wl_type:%d",
cfqd->serving_prio, cfqd->serving_type);
cfq_blkiocg_update_avg_queue_size_stats(&cfqq->cfqg->blkg);
cfqq->slice_start = 0;
cfqq->dispatch_start = jiffies;
cfqq->allocated_slice = 0;
cfqq->slice_end = 0;
cfqq->slice_dispatch = 0;
cfqq->nr_sectors = 0;
cfq_clear_cfqq_wait_request(cfqq);
cfq_clear_cfqq_must_dispatch(cfqq);
cfq_clear_cfqq_must_alloc_slice(cfqq);
cfq_clear_cfqq_fifo_expire(cfqq);
cfq_mark_cfqq_slice_new(cfqq);
cfq_del_timer(cfqd, cfqq);
}
cfqd->active_queue = cfqq;
}
/*
* current cfqq expired its slice (or was too idle), select new one
*/
static void
__cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
bool timed_out)
{
cfq_log_cfqq(cfqd, cfqq, "slice expired t=%d", timed_out);
if (cfq_cfqq_wait_request(cfqq))
cfq_del_timer(cfqd, cfqq);
cfq_clear_cfqq_wait_request(cfqq);
cfq_clear_cfqq_wait_busy(cfqq);
/*
* If this cfqq is shared between multiple processes, check to
* make sure that those processes are still issuing I/Os within
* the mean seek distance. If not, it may be time to break the
* queues apart again.
*/
if (cfq_cfqq_coop(cfqq) && CFQQ_SEEKY(cfqq))
cfq_mark_cfqq_split_coop(cfqq);
/*
* store what was left of this slice, if the queue idled/timed out
*/
if (timed_out) {
if (cfq_cfqq_slice_new(cfqq))
cfqq->slice_resid = cfq_scaled_cfqq_slice(cfqd, cfqq);
else
cfqq->slice_resid = cfqq->slice_end - jiffies;
cfq_log_cfqq(cfqd, cfqq, "resid=%ld", cfqq->slice_resid);
}
cfq_group_served(cfqd, cfqq->cfqg, cfqq);
if (cfq_cfqq_on_rr(cfqq) && RB_EMPTY_ROOT(&cfqq->sort_list))
cfq_del_cfqq_rr(cfqd, cfqq);
cfq_resort_rr_list(cfqd, cfqq);
if (cfqq == cfqd->active_queue)
cfqd->active_queue = NULL;
if (cfqd->active_cic) {
put_io_context(cfqd->active_cic->ioc);
cfqd->active_cic = NULL;
}
}
static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
{
struct cfq_queue *cfqq = cfqd->active_queue;
if (cfqq)
__cfq_slice_expired(cfqd, cfqq, timed_out);
}
/*
* Get next queue for service. Unless we have a queue preemption,
* we'll simply select the first cfqq in the service tree.
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
struct cfq_rb_root *service_tree =
service_tree_for(cfqd->serving_group, cfqd->serving_prio,
cfqd->serving_type);
if (!cfqd->rq_queued)
return NULL;
/* There is nothing to dispatch */
if (!service_tree)
return NULL;
if (RB_EMPTY_ROOT(&service_tree->rb))
return NULL;
return cfq_rb_first(service_tree);
}
static struct cfq_queue *cfq_get_next_queue_forced(struct cfq_data *cfqd)
{
struct cfq_group *cfqg;
struct cfq_queue *cfqq;
int i, j;
struct cfq_rb_root *st;
if (!cfqd->rq_queued)
return NULL;
cfqg = cfq_get_next_cfqg(cfqd);
if (!cfqg)
return NULL;
for_each_cfqg_st(cfqg, i, j, st)
if ((cfqq = cfq_rb_first(st)) != NULL)
return cfqq;
return NULL;
}
/*
* Get and set a new active queue for service.
*/
static struct cfq_queue *cfq_set_active_queue(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
if (!cfqq)
cfqq = cfq_get_next_queue(cfqd);
__cfq_set_active_queue(cfqd, cfqq);
return cfqq;
}
static inline sector_t cfq_dist_from_last(struct cfq_data *cfqd,
struct request *rq)
{
if (blk_rq_pos(rq) >= cfqd->last_position)
return blk_rq_pos(rq) - cfqd->last_position;
else
return cfqd->last_position - blk_rq_pos(rq);
}
static inline int cfq_rq_close(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
return cfq_dist_from_last(cfqd, rq) <= CFQQ_CLOSE_THR;
}
static struct cfq_queue *cfqq_close(struct cfq_data *cfqd,
struct cfq_queue *cur_cfqq)
{
struct rb_root *root = &cfqd->prio_trees[cur_cfqq->org_ioprio];
struct rb_node *parent, *node;
struct cfq_queue *__cfqq;
sector_t sector = cfqd->last_position;
if (RB_EMPTY_ROOT(root))
return NULL;
/*
* First, if we find a request starting at the end of the last
* request, choose it.
*/
__cfqq = cfq_prio_tree_lookup(cfqd, root, sector, &parent, NULL);
if (__cfqq)
return __cfqq;
/*
* If the exact sector wasn't found, the parent of the NULL leaf
* will contain the closest sector.
*/
__cfqq = rb_entry(parent, struct cfq_queue, p_node);
if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
return __cfqq;
if (blk_rq_pos(__cfqq->next_rq) < sector)
node = rb_next(&__cfqq->p_node);
else
node = rb_prev(&__cfqq->p_node);
if (!node)
return NULL;
__cfqq = rb_entry(node, struct cfq_queue, p_node);
if (cfq_rq_close(cfqd, cur_cfqq, __cfqq->next_rq))
return __cfqq;
return NULL;
}
/*
* cfqd - obvious
* cur_cfqq - passed in so that we don't decide that the current queue is
* closely cooperating with itself.
*
* So, basically we're assuming that that cur_cfqq has dispatched at least
* one request, and that cfqd->last_position reflects a position on the disk
* associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
* assumption.
*/
static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
struct cfq_queue *cur_cfqq)
{
struct cfq_queue *cfqq;
if (cfq_class_idle(cur_cfqq))
return NULL;
if (!cfq_cfqq_sync(cur_cfqq))
return NULL;
if (CFQQ_SEEKY(cur_cfqq))
return NULL;
/*
* Don't search priority tree if it's the only queue in the group.
*/
if (cur_cfqq->cfqg->nr_cfqq == 1)
return NULL;
/*
* We should notice if some of the queues are cooperating, eg
* working closely on the same area of the disk. In that case,
* we can group them together and don't waste time idling.
*/
cfqq = cfqq_close(cfqd, cur_cfqq);
if (!cfqq)
return NULL;
/* If new queue belongs to different cfq_group, don't choose it */
if (cur_cfqq->cfqg != cfqq->cfqg)
return NULL;
/*
* It only makes sense to merge sync queues.
*/
if (!cfq_cfqq_sync(cfqq))
return NULL;
if (CFQQ_SEEKY(cfqq))
return NULL;
/*
* Do not merge queues of different priority classes
*/
if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
return NULL;
return cfqq;
}
/*
* Determine whether we should enforce idle window for this queue.
*/
static bool cfq_should_idle(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
enum wl_prio_t prio = cfqq_prio(cfqq);
struct cfq_rb_root *service_tree = cfqq->service_tree;
BUG_ON(!service_tree);
BUG_ON(!service_tree->count);
if (!cfqd->cfq_slice_idle)
return false;
/* We never do for idle class queues. */
if (prio == IDLE_WORKLOAD)
return false;
/* We do for queues that were marked with idle window flag. */
if (cfq_cfqq_idle_window(cfqq) &&
!(blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag))
return true;
/*
* Otherwise, we do only if they are the last ones
* in their service tree.
*/
if (service_tree->count == 1 && cfq_cfqq_sync(cfqq))
return true;
cfq_log_cfqq(cfqd, cfqq, "Not idling. st->count:%d",
service_tree->count);
return false;
}
static void cfq_arm_slice_timer(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = cfqd->active_queue;
struct cfq_io_context *cic;
unsigned long sl, group_idle = 0;
/*
* SSD device without seek penalty, disable idling. But only do so
* for devices that support queuing, otherwise we still have a problem
* with sync vs async workloads.
*/
if (blk_queue_nonrot(cfqd->queue) && cfqd->hw_tag)
return;
WARN_ON(!RB_EMPTY_ROOT(&cfqq->sort_list));
WARN_ON(cfq_cfqq_slice_new(cfqq));
/*
* idle is disabled, either manually or by past process history
*/
if (!cfq_should_idle(cfqd, cfqq)) {
/* no queue idling. Check for group idling */
if (cfqd->cfq_group_idle)
group_idle = cfqd->cfq_group_idle;
else
return;
}
/*
* still active requests from this queue, don't idle
*/
if (cfqq->dispatched)
return;
/*
* task has exited, don't wait
*/
cic = cfqd->active_cic;
if (!cic || !atomic_read(&cic->ioc->nr_tasks))
return;
/*
* If our average think time is larger than the remaining time
* slice, then don't idle. This avoids overrunning the allotted
* time slice.
*/
if (sample_valid(cic->ttime_samples) &&
(cfqq->slice_end - jiffies < cic->ttime_mean)) {
cfq_log_cfqq(cfqd, cfqq, "Not idling. think_time:%d",
cic->ttime_mean);
return;
}
/* There are other queues in the group, don't do group idle */
if (group_idle && cfqq->cfqg->nr_cfqq > 1)
return;
cfq_mark_cfqq_wait_request(cfqq);
if (group_idle)
sl = cfqd->cfq_group_idle;
else
sl = cfqd->cfq_slice_idle;
mod_timer(&cfqd->idle_slice_timer, jiffies + sl);
cfq_blkiocg_update_set_idle_time_stats(&cfqq->cfqg->blkg);
cfq_log_cfqq(cfqd, cfqq, "arm_idle: %lu group_idle: %d", sl,
group_idle ? 1 : 0);
}
/*
* Move request from internal lists to the request queue dispatch list.
*/
static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);
cfq_log_cfqq(cfqd, cfqq, "dispatch_insert");
cfqq->next_rq = cfq_find_next_rq(cfqd, cfqq, rq);
cfq_remove_request(rq);
cfqq->dispatched++;
(RQ_CFQG(rq))->dispatched++;
elv_dispatch_sort(q, rq);
cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
cfqq->nr_sectors += blk_rq_sectors(rq);
cfq_blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
rq_data_dir(rq), rq_is_sync(rq));
}
/*
* return expired entry, or NULL to just start from scratch in rbtree
*/
static struct request *cfq_check_fifo(struct cfq_queue *cfqq)
{
struct request *rq = NULL;
if (cfq_cfqq_fifo_expire(cfqq))
return NULL;
cfq_mark_cfqq_fifo_expire(cfqq);
if (list_empty(&cfqq->fifo))
return NULL;
rq = rq_entry_fifo(cfqq->fifo.next);
if (time_before(jiffies, rq_fifo_time(rq)))
rq = NULL;
cfq_log_cfqq(cfqq->cfqd, cfqq, "fifo=%p", rq);
return rq;
}
static inline int
cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
const int base_rq = cfqd->cfq_slice_async_rq;
WARN_ON(cfqq->ioprio >= IOPRIO_BE_NR);
return 2 * (base_rq + base_rq * (CFQ_PRIO_LISTS - 1 - cfqq->ioprio));
}
/*
* Must be called with the queue_lock held.
*/
static int cfqq_process_refs(struct cfq_queue *cfqq)
{
int process_refs, io_refs;
io_refs = cfqq->allocated[READ] + cfqq->allocated[WRITE];
process_refs = cfqq->ref - io_refs;
BUG_ON(process_refs < 0);
return process_refs;
}
static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
{
int process_refs, new_process_refs;
struct cfq_queue *__cfqq;
/*
* If there are no process references on the new_cfqq, then it is
* unsafe to follow the ->new_cfqq chain as other cfqq's in the
* chain may have dropped their last reference (not just their
* last process reference).
*/
if (!cfqq_process_refs(new_cfqq))
return;
/* Avoid a circular list and skip interim queue merges */
while ((__cfqq = new_cfqq->new_cfqq)) {
if (__cfqq == cfqq)
return;
new_cfqq = __cfqq;
}
process_refs = cfqq_process_refs(cfqq);
new_process_refs = cfqq_process_refs(new_cfqq);
/*
* If the process for the cfqq has gone away, there is no
* sense in merging the queues.
*/
if (process_refs == 0 || new_process_refs == 0)
return;
/*
* Merge in the direction of the lesser amount of work.
*/
if (new_process_refs >= process_refs) {
cfqq->new_cfqq = new_cfqq;
new_cfqq->ref += process_refs;
} else {
new_cfqq->new_cfqq = cfqq;
cfqq->ref += new_process_refs;
}
}
static enum wl_type_t cfq_choose_wl(struct cfq_data *cfqd,
struct cfq_group *cfqg, enum wl_prio_t prio)
{
struct cfq_queue *queue;
int i;
bool key_valid = false;
unsigned long lowest_key = 0;
enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
for (i = 0; i <= SYNC_WORKLOAD; ++i) {
/* select the one with lowest rb_key */
queue = cfq_rb_first(service_tree_for(cfqg, prio, i));
if (queue &&
(!key_valid || time_before(queue->rb_key, lowest_key))) {
lowest_key = queue->rb_key;
cur_best = i;
key_valid = true;
}
}
return cur_best;
}
static void choose_service_tree(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
unsigned slice;
unsigned count;
struct cfq_rb_root *st;
unsigned group_slice;
enum wl_prio_t original_prio = cfqd->serving_prio;
/* Choose next priority. RT > BE > IDLE */
if (cfq_group_busy_queues_wl(RT_WORKLOAD, cfqd, cfqg))
cfqd->serving_prio = RT_WORKLOAD;
else if (cfq_group_busy_queues_wl(BE_WORKLOAD, cfqd, cfqg))
cfqd->serving_prio = BE_WORKLOAD;
else {
cfqd->serving_prio = IDLE_WORKLOAD;
cfqd->workload_expires = jiffies + 1;
return;
}
if (original_prio != cfqd->serving_prio)
goto new_workload;
/*
* For RT and BE, we have to choose also the type
* (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
* expiration time
*/
st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
count = st->count;
/*
* check workload expiration, and that we still have other queues ready
*/
if (count && !time_after(jiffies, cfqd->workload_expires))
return;
new_workload:
/* otherwise select new workload type */
cfqd->serving_type =
cfq_choose_wl(cfqd, cfqg, cfqd->serving_prio);
st = service_tree_for(cfqg, cfqd->serving_prio, cfqd->serving_type);
count = st->count;
/*
* the workload slice is computed as a fraction of target latency
* proportional to the number of queues in that workload, over
* all the queues in the same priority class
*/
group_slice = cfq_group_slice(cfqd, cfqg);
slice = group_slice * count /
max_t(unsigned, cfqg->busy_queues_avg[cfqd->serving_prio],
cfq_group_busy_queues_wl(cfqd->serving_prio, cfqd, cfqg));
if (cfqd->serving_type == ASYNC_WORKLOAD) {
unsigned int tmp;
/*
* Async queues are currently system wide. Just taking
* proportion of queues with-in same group will lead to higher
* async ratio system wide as generally root group is going
* to have higher weight. A more accurate thing would be to
* calculate system wide asnc/sync ratio.
*/
tmp = cfq_target_latency * cfqg_busy_async_queues(cfqd, cfqg);
tmp = tmp/cfqd->busy_queues;
slice = min_t(unsigned, slice, tmp);
/* async workload slice is scaled down according to
* the sync/async slice ratio. */
slice = slice * cfqd->cfq_slice[0] / cfqd->cfq_slice[1];
} else
/* sync workload slice is at least 2 * cfq_slice_idle */
slice = max(slice, 2 * cfqd->cfq_slice_idle);
slice = max_t(unsigned, slice, CFQ_MIN_TT);
cfq_log(cfqd, "workload slice:%d", slice);
cfqd->workload_expires = jiffies + slice;
}
static struct cfq_group *cfq_get_next_cfqg(struct cfq_data *cfqd)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
struct cfq_group *cfqg;
if (RB_EMPTY_ROOT(&st->rb))
return NULL;
cfqg = cfq_rb_first_group(st);
update_min_vdisktime(st);
return cfqg;
}
static void cfq_choose_cfqg(struct cfq_data *cfqd)
{
struct cfq_group *cfqg = cfq_get_next_cfqg(cfqd);
cfqd->serving_group = cfqg;
/* Restore the workload type data */
if (cfqg->saved_workload_slice) {
cfqd->workload_expires = jiffies + cfqg->saved_workload_slice;
cfqd->serving_type = cfqg->saved_workload;
cfqd->serving_prio = cfqg->saved_serving_prio;
} else
cfqd->workload_expires = jiffies - 1;
choose_service_tree(cfqd, cfqg);
}
/*
* Select a queue for service. If we have a current active queue,
* check whether to continue servicing it, or retrieve and set a new one.
*/
static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
cfqq = cfqd->active_queue;
if (!cfqq)
goto new_queue;
if (!cfqd->rq_queued)
return NULL;
/*
* We were waiting for group to get backlogged. Expire the queue
*/
if (cfq_cfqq_wait_busy(cfqq) && !RB_EMPTY_ROOT(&cfqq->sort_list))
goto expire;
/*
* The active queue has run out of time, expire it and select new.
*/
if (cfq_slice_used(cfqq) && !cfq_cfqq_must_dispatch(cfqq)) {
/*
* If slice had not expired at the completion of last request
* we might not have turned on wait_busy flag. Don't expire
* the queue yet. Allow the group to get backlogged.
*
* The very fact that we have used the slice, that means we
* have been idling all along on this queue and it should be
* ok to wait for this request to complete.
*/
if (cfqq->cfqg->nr_cfqq == 1 && RB_EMPTY_ROOT(&cfqq->sort_list)
&& cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
cfqq = NULL;
goto keep_queue;
} else
goto check_group_idle;
}
/*
* The active queue has requests and isn't expired, allow it to
* dispatch.
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
goto keep_queue;
/*
* If another queue has a request waiting within our mean seek
* distance, let it run. The expire code will check for close
* cooperators and put the close queue at the front of the service
* tree. If possible, merge the expiring queue with the new cfqq.
*/
new_cfqq = cfq_close_cooperator(cfqd, cfqq);
if (new_cfqq) {
if (!cfqq->new_cfqq)
cfq_setup_merge(cfqq, new_cfqq);
goto expire;
}
/*
* No requests pending. If the active queue still has requests in
* flight or is idling for a new request, allow either of these
* conditions to happen (or time out) before selecting a new queue.
*/
if (timer_pending(&cfqd->idle_slice_timer)) {
cfqq = NULL;
goto keep_queue;
}
/*
* This is a deep seek queue, but the device is much faster than
* the queue can deliver, don't idle
**/
if (CFQQ_SEEKY(cfqq) && cfq_cfqq_idle_window(cfqq) &&
(cfq_cfqq_slice_new(cfqq) ||
(cfqq->slice_end - jiffies > jiffies - cfqq->slice_start))) {
cfq_clear_cfqq_deep(cfqq);
cfq_clear_cfqq_idle_window(cfqq);
}
if (cfqq->dispatched && cfq_should_idle(cfqd, cfqq)) {
cfqq = NULL;
goto keep_queue;
}
/*
* If group idle is enabled and there are requests dispatched from
* this group, wait for requests to complete.
*/
check_group_idle:
if (cfqd->cfq_group_idle && cfqq->cfqg->nr_cfqq == 1
&& cfqq->cfqg->dispatched) {
cfqq = NULL;
goto keep_queue;
}
expire:
cfq_slice_expired(cfqd, 0);
new_queue:
/*
* Current queue expired. Check if we have to switch to a new
* service tree
*/
if (!new_cfqq)
cfq_choose_cfqg(cfqd);
cfqq = cfq_set_active_queue(cfqd, new_cfqq);
keep_queue:
return cfqq;
}
static int __cfq_forced_dispatch_cfqq(struct cfq_queue *cfqq)
{
int dispatched = 0;
while (cfqq->next_rq) {
cfq_dispatch_insert(cfqq->cfqd->queue, cfqq->next_rq);
dispatched++;
}
BUG_ON(!list_empty(&cfqq->fifo));
/* By default cfqq is not expired if it is empty. Do it explicitly */
__cfq_slice_expired(cfqq->cfqd, cfqq, 0);
return dispatched;
}
/*
* Drain our current requests. Used for barriers and when switching
* io schedulers on-the-fly.
*/
static int cfq_forced_dispatch(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq;
int dispatched = 0;
/* Expire the timeslice of the current active queue first */
cfq_slice_expired(cfqd, 0);
while ((cfqq = cfq_get_next_queue_forced(cfqd)) != NULL) {
__cfq_set_active_queue(cfqd, cfqq);
dispatched += __cfq_forced_dispatch_cfqq(cfqq);
}
BUG_ON(cfqd->busy_queues);
cfq_log(cfqd, "forced_dispatch=%d", dispatched);
return dispatched;
}
static inline bool cfq_slice_used_soon(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
/* the queue hasn't finished any request, can't estimate */
if (cfq_cfqq_slice_new(cfqq))
return true;
if (time_after(jiffies + cfqd->cfq_slice_idle * cfqq->dispatched,
cfqq->slice_end))
return true;
return false;
}
static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
unsigned int max_dispatch;
/*
* Drain async requests before we start sync IO
*/
if (cfq_should_idle(cfqd, cfqq) && cfqd->rq_in_flight[BLK_RW_ASYNC])
return false;
/*
* If this is an async queue and we have sync IO in flight, let it wait
*/
if (cfqd->rq_in_flight[BLK_RW_SYNC] && !cfq_cfqq_sync(cfqq))
return false;
max_dispatch = max_t(unsigned int, cfqd->cfq_quantum / 2, 1);
if (cfq_class_idle(cfqq))
max_dispatch = 1;
/*
* Does this cfqq already have too much IO in flight?
*/
if (cfqq->dispatched >= max_dispatch) {
bool promote_sync = false;
/*
* idle queue must always only have a single IO in flight
*/
if (cfq_class_idle(cfqq))
return false;
/*
* If there is only one sync queue
* we can ignore async queue here and give the sync
* queue no dispatch limit. The reason is a sync queue can
* preempt async queue, limiting the sync queue doesn't make
* sense. This is useful for aiostress test.
*/
if (cfq_cfqq_sync(cfqq) && cfqd->busy_sync_queues == 1)
promote_sync = true;
/*
* We have other queues, don't allow more IO from this one
*/
if (cfqd->busy_queues > 1 && cfq_slice_used_soon(cfqd, cfqq) &&
!promote_sync)
return false;
/*
* Sole queue user, no limit
*/
if (cfqd->busy_queues == 1 || promote_sync)
max_dispatch = -1;
else
/*
* Normally we start throttling cfqq when cfq_quantum/2
* requests have been dispatched. But we can drive
* deeper queue depths at the beginning of slice
* subjected to upper limit of cfq_quantum.
* */
max_dispatch = cfqd->cfq_quantum;
}
/*
* Async queues must wait a bit before being allowed dispatch.
* We also ramp up the dispatch depth gradually for async IO,
* based on the last sync IO we serviced
*/
if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
unsigned int depth;
depth = last_sync / cfqd->cfq_slice[1];
if (!depth && !cfqq->dispatched)
depth = 1;
if (depth < max_dispatch)
max_dispatch = depth;
}
/*
* If we're below the current max, allow a dispatch
*/
return cfqq->dispatched < max_dispatch;
}
/*
* Dispatch a request from cfqq, moving them to the request queue
* dispatch list.
*/
static bool cfq_dispatch_request(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct request *rq;
BUG_ON(RB_EMPTY_ROOT(&cfqq->sort_list));
if (!cfq_may_dispatch(cfqd, cfqq))
return false;
/*
* follow expired path, else get first next available
*/
rq = cfq_check_fifo(cfqq);
if (!rq)
rq = cfqq->next_rq;
/*
* insert request into driver dispatch list
*/
cfq_dispatch_insert(cfqd->queue, rq);
if (!cfqd->active_cic) {
struct cfq_io_context *cic = RQ_CIC(rq);
atomic_long_inc(&cic->ioc->refcount);
cfqd->active_cic = cic;
}
return true;
}
/*
* Find the cfqq that we need to service and move a request from that to the
* dispatch list
*/
static int cfq_dispatch_requests(struct request_queue *q, int force)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq;
if (!cfqd->busy_queues)
return 0;
if (unlikely(force))
return cfq_forced_dispatch(cfqd);
cfqq = cfq_select_queue(cfqd);
if (!cfqq)
return 0;
/*
* Dispatch a request from this cfqq, if it is allowed
*/
if (!cfq_dispatch_request(cfqd, cfqq))
return 0;
cfqq->slice_dispatch++;
cfq_clear_cfqq_must_dispatch(cfqq);
/*
* expire an async queue immediately if it has used up its slice. idle
* queue always expire after 1 dispatch round.
*/
if (cfqd->busy_queues > 1 && ((!cfq_cfqq_sync(cfqq) &&
cfqq->slice_dispatch >= cfq_prio_to_maxrq(cfqd, cfqq)) ||
cfq_class_idle(cfqq))) {
cfqq->slice_end = jiffies + 1;
cfq_slice_expired(cfqd, 0);
}
cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
return 1;
}
/*
* task holds one reference to the queue, dropped when task exits. each rq
* in-flight on this queue also holds a reference, dropped when rq is freed.
*
* Each cfq queue took a reference on the parent group. Drop it now.
* queue lock must be held here.
*/
static void cfq_put_queue(struct cfq_queue *cfqq)
{
struct cfq_data *cfqd = cfqq->cfqd;
struct cfq_group *cfqg;
BUG_ON(cfqq->ref <= 0);
cfqq->ref--;
if (cfqq->ref)
return;
cfq_log_cfqq(cfqd, cfqq, "put_queue");
BUG_ON(rb_first(&cfqq->sort_list));
BUG_ON(cfqq->allocated[READ] + cfqq->allocated[WRITE]);
cfqg = cfqq->cfqg;
if (unlikely(cfqd->active_queue == cfqq)) {
__cfq_slice_expired(cfqd, cfqq, 0);
cfq_schedule_dispatch(cfqd);
}
BUG_ON(cfq_cfqq_on_rr(cfqq));
kmem_cache_free(cfq_pool, cfqq);
cfq_put_cfqg(cfqg);
}
/*
* Call func for each cic attached to this ioc.
*/
static void
call_for_each_cic(struct io_context *ioc,
void (*func)(struct io_context *, struct cfq_io_context *))
{
struct cfq_io_context *cic;
struct hlist_node *n;
rcu_read_lock();
hlist_for_each_entry_rcu(cic, n, &ioc->cic_list, cic_list)
func(ioc, cic);
rcu_read_unlock();
}
static void cfq_cic_free_rcu(struct rcu_head *head)
{
struct cfq_io_context *cic;
cic = container_of(head, struct cfq_io_context, rcu_head);
kmem_cache_free(cfq_ioc_pool, cic);
elv_ioc_count_dec(cfq_ioc_count);
if (ioc_gone) {
/*
* CFQ scheduler is exiting, grab exit lock and check
* the pending io context count. If it hits zero,
* complete ioc_gone and set it back to NULL
*/
spin_lock(&ioc_gone_lock);
if (ioc_gone && !elv_ioc_count_read(cfq_ioc_count)) {
complete(ioc_gone);
ioc_gone = NULL;
}
spin_unlock(&ioc_gone_lock);
}
}
static void cfq_cic_free(struct cfq_io_context *cic)
{
call_rcu(&cic->rcu_head, cfq_cic_free_rcu);
}
static void cic_free_func(struct io_context *ioc, struct cfq_io_context *cic)
{
unsigned long flags;
unsigned long dead_key = (unsigned long) cic->key;
BUG_ON(!(dead_key & CIC_DEAD_KEY));
spin_lock_irqsave(&ioc->lock, flags);
radix_tree_delete(&ioc->radix_root, dead_key >> CIC_DEAD_INDEX_SHIFT);
hlist_del_rcu(&cic->cic_list);
spin_unlock_irqrestore(&ioc->lock, flags);
cfq_cic_free(cic);
}
/*
* Must be called with rcu_read_lock() held or preemption otherwise disabled.
* Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
* and ->trim() which is called with the task lock held
*/
static void cfq_free_io_context(struct io_context *ioc)
{
/*
* ioc->refcount is zero here, or we are called from elv_unregister(),
* so no more cic's are allowed to be linked into this ioc. So it
* should be ok to iterate over the known list, we will see all cic's
* since no new ones are added.
*/
call_for_each_cic(ioc, cic_free_func);
}
static void cfq_put_cooperator(struct cfq_queue *cfqq)
{
struct cfq_queue *__cfqq, *next;
/*
* If this queue was scheduled to merge with another queue, be
* sure to drop the reference taken on that queue (and others in
* the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
*/
__cfqq = cfqq->new_cfqq;
while (__cfqq) {
if (__cfqq == cfqq) {
WARN(1, "cfqq->new_cfqq loop detected\n");
break;
}
next = __cfqq->new_cfqq;
cfq_put_queue(__cfqq);
__cfqq = next;
}
}
static void cfq_exit_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
if (unlikely(cfqq == cfqd->active_queue)) {
__cfq_slice_expired(cfqd, cfqq, 0);
cfq_schedule_dispatch(cfqd);
}
cfq_put_cooperator(cfqq);
cfq_put_queue(cfqq);
}
static void __cfq_exit_single_io_context(struct cfq_data *cfqd,
struct cfq_io_context *cic)
{
struct io_context *ioc = cic->ioc;
list_del_init(&cic->queue_list);
/*
* Make sure dead mark is seen for dead queues
*/
smp_wmb();
cic->key = cfqd_dead_key(cfqd);
if (ioc->ioc_data == cic)
rcu_assign_pointer(ioc->ioc_data, NULL);
if (cic->cfqq[BLK_RW_ASYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_ASYNC]);
cic->cfqq[BLK_RW_ASYNC] = NULL;
}
if (cic->cfqq[BLK_RW_SYNC]) {
cfq_exit_cfqq(cfqd, cic->cfqq[BLK_RW_SYNC]);
cic->cfqq[BLK_RW_SYNC] = NULL;
}
}
static void cfq_exit_single_io_context(struct io_context *ioc,
struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic_to_cfqd(cic);
if (cfqd) {
struct request_queue *q = cfqd->queue;
unsigned long flags;
spin_lock_irqsave(q->queue_lock, flags);
/*
* Ensure we get a fresh copy of the ->key to prevent
* race between exiting task and queue
*/
smp_read_barrier_depends();
if (cic->key == cfqd)
__cfq_exit_single_io_context(cfqd, cic);
spin_unlock_irqrestore(q->queue_lock, flags);
}
}
/*
* The process that ioc belongs to has exited, we need to clean up
* and put the internal structures we have that belongs to that process.
*/
static void cfq_exit_io_context(struct io_context *ioc)
{
call_for_each_cic(ioc, cfq_exit_single_io_context);
}
static struct cfq_io_context *
cfq_alloc_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
{
struct cfq_io_context *cic;
cic = kmem_cache_alloc_node(cfq_ioc_pool, gfp_mask | __GFP_ZERO,
cfqd->queue->node);
if (cic) {
cic->last_end_request = jiffies;
INIT_LIST_HEAD(&cic->queue_list);
INIT_HLIST_NODE(&cic->cic_list);
cic->dtor = cfq_free_io_context;
cic->exit = cfq_exit_io_context;
elv_ioc_count_inc(cfq_ioc_count);
}
return cic;
}
static void cfq_init_prio_data(struct cfq_queue *cfqq, struct io_context *ioc)
{
struct task_struct *tsk = current;
int ioprio_class;
if (!cfq_cfqq_prio_changed(cfqq))
return;
ioprio_class = IOPRIO_PRIO_CLASS(ioc->ioprio);
switch (ioprio_class) {
default:
printk(KERN_ERR "cfq: bad prio %x\n", ioprio_class);
case IOPRIO_CLASS_NONE:
/*
* no prio set, inherit CPU scheduling settings
*/
cfqq->ioprio = task_nice_ioprio(tsk);
cfqq->ioprio_class = task_nice_ioclass(tsk);
break;
case IOPRIO_CLASS_RT:
cfqq->ioprio = task_ioprio(ioc);
cfqq->ioprio_class = IOPRIO_CLASS_RT;
break;
case IOPRIO_CLASS_BE:
cfqq->ioprio = task_ioprio(ioc);
cfqq->ioprio_class = IOPRIO_CLASS_BE;
break;
case IOPRIO_CLASS_IDLE:
cfqq->ioprio_class = IOPRIO_CLASS_IDLE;
cfqq->ioprio = 7;
cfq_clear_cfqq_idle_window(cfqq);
break;
}
/*
* keep track of original prio settings in case we have to temporarily
* elevate the priority of this queue
*/
cfqq->org_ioprio = cfqq->ioprio;
cfqq->org_ioprio_class = cfqq->ioprio_class;
cfq_clear_cfqq_prio_changed(cfqq);
}
static void changed_ioprio(struct io_context *ioc, struct cfq_io_context *cic)
{
struct cfq_data *cfqd = cic_to_cfqd(cic);
struct cfq_queue *cfqq;
unsigned long flags;
if (unlikely(!cfqd))
return;
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
cfqq = cic->cfqq[BLK_RW_ASYNC];
if (cfqq) {
struct cfq_queue *new_cfqq;
new_cfqq = cfq_get_queue(cfqd, BLK_RW_ASYNC, cic->ioc,
GFP_ATOMIC);
if (new_cfqq) {
cic->cfqq[BLK_RW_ASYNC] = new_cfqq;
cfq_put_queue(cfqq);
}
}
cfqq = cic->cfqq[BLK_RW_SYNC];
if (cfqq)
cfq_mark_cfqq_prio_changed(cfqq);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
static void cfq_ioc_set_ioprio(struct io_context *ioc)
{
call_for_each_cic(ioc, changed_ioprio);
ioc->ioprio_changed = 0;
}
static void cfq_init_cfqq(struct cfq_data *cfqd, struct cfq_queue *cfqq,
pid_t pid, bool is_sync)
{
RB_CLEAR_NODE(&cfqq->rb_node);
RB_CLEAR_NODE(&cfqq->p_node);
INIT_LIST_HEAD(&cfqq->fifo);
cfqq->ref = 0;
cfqq->cfqd = cfqd;
cfq_mark_cfqq_prio_changed(cfqq);
if (is_sync) {
if (!cfq_class_idle(cfqq))
cfq_mark_cfqq_idle_window(cfqq);
cfq_mark_cfqq_sync(cfqq);
}
cfqq->pid = pid;
}
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static void changed_cgroup(struct io_context *ioc, struct cfq_io_context *cic)
{
struct cfq_queue *sync_cfqq = cic_to_cfqq(cic, 1);
struct cfq_data *cfqd = cic_to_cfqd(cic);
unsigned long flags;
struct request_queue *q;
if (unlikely(!cfqd))
return;
q = cfqd->queue;
spin_lock_irqsave(q->queue_lock, flags);
if (sync_cfqq) {
/*
* Drop reference to sync queue. A new sync queue will be
* assigned in new group upon arrival of a fresh request.
*/
cfq_log_cfqq(cfqd, sync_cfqq, "changed cgroup");
cic_set_cfqq(cic, NULL, 1);
cfq_put_queue(sync_cfqq);
}
spin_unlock_irqrestore(q->queue_lock, flags);
}
static void cfq_ioc_set_cgroup(struct io_context *ioc)
{
call_for_each_cic(ioc, changed_cgroup);
ioc->cgroup_changed = 0;
}
#endif /* CONFIG_CFQ_GROUP_IOSCHED */
static struct cfq_queue *
cfq_find_alloc_queue(struct cfq_data *cfqd, bool is_sync,
struct io_context *ioc, gfp_t gfp_mask)
{
struct cfq_queue *cfqq, *new_cfqq = NULL;
struct cfq_io_context *cic;
struct cfq_group *cfqg;
retry:
cfqg = cfq_get_cfqg(cfqd, 1);
cic = cfq_cic_lookup(cfqd, ioc);
/* cic always exists here */
cfqq = cic_to_cfqq(cic, is_sync);
/*
* Always try a new alloc if we fell back to the OOM cfqq
* originally, since it should just be a temporary situation.
*/
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
cfqq = NULL;
if (new_cfqq) {
cfqq = new_cfqq;
new_cfqq = NULL;
} else if (gfp_mask & __GFP_WAIT) {
spin_unlock_irq(cfqd->queue->queue_lock);
new_cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
spin_lock_irq(cfqd->queue->queue_lock);
if (new_cfqq)
goto retry;
} else {
cfqq = kmem_cache_alloc_node(cfq_pool,
gfp_mask | __GFP_ZERO,
cfqd->queue->node);
}
if (cfqq) {
cfq_init_cfqq(cfqd, cfqq, current->pid, is_sync);
cfq_init_prio_data(cfqq, ioc);
cfq_link_cfqq_cfqg(cfqq, cfqg);
cfq_log_cfqq(cfqd, cfqq, "alloced");
} else
cfqq = &cfqd->oom_cfqq;
}
if (new_cfqq)
kmem_cache_free(cfq_pool, new_cfqq);
return cfqq;
}
static struct cfq_queue **
cfq_async_queue_prio(struct cfq_data *cfqd, int ioprio_class, int ioprio)
{
switch (ioprio_class) {
case IOPRIO_CLASS_RT:
return &cfqd->async_cfqq[0][ioprio];
case IOPRIO_CLASS_BE:
return &cfqd->async_cfqq[1][ioprio];
case IOPRIO_CLASS_IDLE:
return &cfqd->async_idle_cfqq;
default:
BUG();
}
}
static struct cfq_queue *
cfq_get_queue(struct cfq_data *cfqd, bool is_sync, struct io_context *ioc,
gfp_t gfp_mask)
{
const int ioprio = task_ioprio(ioc);
const int ioprio_class = task_ioprio_class(ioc);
struct cfq_queue **async_cfqq = NULL;
struct cfq_queue *cfqq = NULL;
if (!is_sync) {
async_cfqq = cfq_async_queue_prio(cfqd, ioprio_class, ioprio);
cfqq = *async_cfqq;
}
if (!cfqq)
cfqq = cfq_find_alloc_queue(cfqd, is_sync, ioc, gfp_mask);
/*
* pin the queue now that it's allocated, scheduler exit will prune it
*/
if (!is_sync && !(*async_cfqq)) {
cfqq->ref++;
*async_cfqq = cfqq;
}
cfqq->ref++;
return cfqq;
}
/*
* We drop cfq io contexts lazily, so we may find a dead one.
*/
static void
cfq_drop_dead_cic(struct cfq_data *cfqd, struct io_context *ioc,
struct cfq_io_context *cic)
{
unsigned long flags;
WARN_ON(!list_empty(&cic->queue_list));
BUG_ON(cic->key != cfqd_dead_key(cfqd));
spin_lock_irqsave(&ioc->lock, flags);
BUG_ON(ioc->ioc_data == cic);
radix_tree_delete(&ioc->radix_root, cfqd->cic_index);
hlist_del_rcu(&cic->cic_list);
spin_unlock_irqrestore(&ioc->lock, flags);
cfq_cic_free(cic);
}
static struct cfq_io_context *
cfq_cic_lookup(struct cfq_data *cfqd, struct io_context *ioc)
{
struct cfq_io_context *cic;
unsigned long flags;
if (unlikely(!ioc))
return NULL;
rcu_read_lock();
/*
* we maintain a last-hit cache, to avoid browsing over the tree
*/
cic = rcu_dereference(ioc->ioc_data);
if (cic && cic->key == cfqd) {
rcu_read_unlock();
return cic;
}
do {
cic = radix_tree_lookup(&ioc->radix_root, cfqd->cic_index);
rcu_read_unlock();
if (!cic)
break;
if (unlikely(cic->key != cfqd)) {
cfq_drop_dead_cic(cfqd, ioc, cic);
rcu_read_lock();
continue;
}
spin_lock_irqsave(&ioc->lock, flags);
rcu_assign_pointer(ioc->ioc_data, cic);
spin_unlock_irqrestore(&ioc->lock, flags);
break;
} while (1);
return cic;
}
/*
* Add cic into ioc, using cfqd as the search key. This enables us to lookup
* the process specific cfq io context when entered from the block layer.
* Also adds the cic to a per-cfqd list, used when this queue is removed.
*/
static int cfq_cic_link(struct cfq_data *cfqd, struct io_context *ioc,
struct cfq_io_context *cic, gfp_t gfp_mask)
{
unsigned long flags;
int ret;
ret = radix_tree_preload(gfp_mask);
if (!ret) {
cic->ioc = ioc;
cic->key = cfqd;
spin_lock_irqsave(&ioc->lock, flags);
ret = radix_tree_insert(&ioc->radix_root,
cfqd->cic_index, cic);
if (!ret)
hlist_add_head_rcu(&cic->cic_list, &ioc->cic_list);
spin_unlock_irqrestore(&ioc->lock, flags);
radix_tree_preload_end();
if (!ret) {
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
list_add(&cic->queue_list, &cfqd->cic_list);
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
}
if (ret)
printk(KERN_ERR "cfq: cic link failed!\n");
return ret;
}
/*
* Setup general io context and cfq io context. There can be several cfq
* io contexts per general io context, if this process is doing io to more
* than one device managed by cfq.
*/
static struct cfq_io_context *
cfq_get_io_context(struct cfq_data *cfqd, gfp_t gfp_mask)
{
struct io_context *ioc = NULL;
struct cfq_io_context *cic;
might_sleep_if(gfp_mask & __GFP_WAIT);
ioc = get_io_context(gfp_mask, cfqd->queue->node);
if (!ioc)
return NULL;
cic = cfq_cic_lookup(cfqd, ioc);
if (cic)
goto out;
cic = cfq_alloc_io_context(cfqd, gfp_mask);
if (cic == NULL)
goto err;
if (cfq_cic_link(cfqd, ioc, cic, gfp_mask))
goto err_free;
out:
smp_read_barrier_depends();
if (unlikely(ioc->ioprio_changed))
cfq_ioc_set_ioprio(ioc);
#ifdef CONFIG_CFQ_GROUP_IOSCHED
if (unlikely(ioc->cgroup_changed))
cfq_ioc_set_cgroup(ioc);
#endif
return cic;
err_free:
cfq_cic_free(cic);
err:
put_io_context(ioc);
return NULL;
}
static void
cfq_update_io_thinktime(struct cfq_data *cfqd, struct cfq_io_context *cic)
{
unsigned long elapsed = jiffies - cic->last_end_request;
unsigned long ttime = min(elapsed, 2UL * cfqd->cfq_slice_idle);
cic->ttime_samples = (7*cic->ttime_samples + 256) / 8;
cic->ttime_total = (7*cic->ttime_total + 256*ttime) / 8;
cic->ttime_mean = (cic->ttime_total + 128) / cic->ttime_samples;
}
static void
cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
sector_t sdist = 0;
sector_t n_sec = blk_rq_sectors(rq);
if (cfqq->last_request_pos) {
if (cfqq->last_request_pos < blk_rq_pos(rq))
sdist = blk_rq_pos(rq) - cfqq->last_request_pos;
else
sdist = cfqq->last_request_pos - blk_rq_pos(rq);
}
cfqq->seek_history <<= 1;
if (blk_queue_nonrot(cfqd->queue))
cfqq->seek_history |= (n_sec < CFQQ_SECT_THR_NONROT);
else
cfqq->seek_history |= (sdist > CFQQ_SEEK_THR);
}
/*
* Disable idle window if the process thinks too long or seeks so much that
* it doesn't matter
*/
static void
cfq_update_idle_window(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct cfq_io_context *cic)
{
int old_idle, enable_idle;
/*
* Don't idle for async or idle io prio class
*/
if (!cfq_cfqq_sync(cfqq) || cfq_class_idle(cfqq))
return;
enable_idle = old_idle = cfq_cfqq_idle_window(cfqq);
if (cfqq->queued[0] + cfqq->queued[1] >= 4)
cfq_mark_cfqq_deep(cfqq);
if (cfqq->next_rq && (cfqq->next_rq->cmd_flags & REQ_NOIDLE))
enable_idle = 0;
else if (!atomic_read(&cic->ioc->nr_tasks) || !cfqd->cfq_slice_idle ||
(!cfq_cfqq_deep(cfqq) && CFQQ_SEEKY(cfqq)))
enable_idle = 0;
else if (sample_valid(cic->ttime_samples)) {
if (cic->ttime_mean > cfqd->cfq_slice_idle)
enable_idle = 0;
else
enable_idle = 1;
}
if (old_idle != enable_idle) {
cfq_log_cfqq(cfqd, cfqq, "idle=%d", enable_idle);
if (enable_idle)
cfq_mark_cfqq_idle_window(cfqq);
else
cfq_clear_cfqq_idle_window(cfqq);
}
}
/*
* Check if new_cfqq should preempt the currently active queue. Return 0 for
* no or if we aren't sure, a 1 will cause a preempt.
*/
static bool
cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
struct request *rq)
{
struct cfq_queue *cfqq;
cfqq = cfqd->active_queue;
if (!cfqq)
return false;
if (cfq_class_idle(new_cfqq))
return false;
if (cfq_class_idle(cfqq))
return true;
/*
* Don't allow a non-RT request to preempt an ongoing RT cfqq timeslice.
*/
if (cfq_class_rt(cfqq) && !cfq_class_rt(new_cfqq))
return false;
/*
* if the new request is sync, but the currently running queue is
* not, let the sync request have priority.
*/
if (rq_is_sync(rq) && !cfq_cfqq_sync(cfqq))
return true;
if (new_cfqq->cfqg != cfqq->cfqg)
return false;
if (cfq_slice_used(cfqq))
return true;
/* Allow preemption only if we are idling on sync-noidle tree */
if (cfqd->serving_type == SYNC_NOIDLE_WORKLOAD &&
cfqq_type(new_cfqq) == SYNC_NOIDLE_WORKLOAD &&
new_cfqq->service_tree->count == 2 &&
RB_EMPTY_ROOT(&cfqq->sort_list))
return true;
/*
* So both queues are sync. Let the new request get disk time if
* it's a metadata request and the current queue is doing regular IO.
*/
if ((rq->cmd_flags & REQ_META) && !cfqq->meta_pending)
return true;
/*
* Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
*/
if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
return true;
/* An idle queue should not be idle now for some reason */
if (RB_EMPTY_ROOT(&cfqq->sort_list) && !cfq_should_idle(cfqd, cfqq))
return true;
if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
return false;
/*
* if this request is as-good as one we would expect from the
* current cfqq, let it preempt
*/
if (cfq_rq_close(cfqd, cfqq, rq))
return true;
return false;
}
/*
* cfqq preempts the active queue. if we allowed preempt with no slice left,
* let it have half of its nominal slice.
*/
static void cfq_preempt_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct cfq_queue *old_cfqq = cfqd->active_queue;
cfq_log_cfqq(cfqd, cfqq, "preempt");
cfq_slice_expired(cfqd, 1);
/*
* workload type is changed, don't save slice, otherwise preempt
* doesn't happen
*/
if (cfqq_type(old_cfqq) != cfqq_type(cfqq))
cfqq->cfqg->saved_workload_slice = 0;
/*
* Put the new queue at the front of the of the current list,
* so we know that it will be selected next.
*/
BUG_ON(!cfq_cfqq_on_rr(cfqq));
cfq_service_tree_add(cfqd, cfqq, 1);
cfqq->slice_end = 0;
cfq_mark_cfqq_slice_new(cfqq);
}
/*
* Called when a new fs request (rq) is added (to cfqq). Check if there's
* something we should do about it
*/
static void
cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
struct request *rq)
{
struct cfq_io_context *cic = RQ_CIC(rq);
cfqd->rq_queued++;
if (rq->cmd_flags & REQ_META)
cfqq->meta_pending++;
cfq_update_io_thinktime(cfqd, cic);
cfq_update_io_seektime(cfqd, cfqq, rq);
cfq_update_idle_window(cfqd, cfqq, cic);
cfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
if (cfqq == cfqd->active_queue) {
/*
* Remember that we saw a request from this process, but
* don't start queuing just yet. Otherwise we risk seeing lots
* of tiny requests, because we disrupt the normal plugging
* and merging. If the request is already larger than a single
* page, let it rip immediately. For that case we assume that
* merging is already done. Ditto for a busy system that
* has other work pending, don't risk delaying until the
* idle timer unplug to continue working.
*/
if (cfq_cfqq_wait_request(cfqq)) {
if (blk_rq_bytes(rq) > PAGE_CACHE_SIZE ||
cfqd->busy_queues > 1) {
cfq_del_timer(cfqd, cfqq);
cfq_clear_cfqq_wait_request(cfqq);
__blk_run_queue(cfqd->queue);
} else {
cfq_blkiocg_update_idle_time_stats(
&cfqq->cfqg->blkg);
cfq_mark_cfqq_must_dispatch(cfqq);
}
}
} else if (cfq_should_preempt(cfqd, cfqq, rq)) {
/*
* not the active queue - expire current slice if it is
* idle and has expired it's mean thinktime or this new queue
* has some old slice time left and is of higher priority or
* this new queue is RT and the current one is BE
*/
cfq_preempt_queue(cfqd, cfqq);
__blk_run_queue(cfqd->queue);
}
}
static void cfq_insert_request(struct request_queue *q, struct request *rq)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_queue *cfqq = RQ_CFQQ(rq);
cfq_log_cfqq(cfqd, cfqq, "insert_request");
cfq_init_prio_data(cfqq, RQ_CIC(rq)->ioc);
rq_set_fifo_time(rq, jiffies + cfqd->cfq_fifo_expire[rq_is_sync(rq)]);
list_add_tail(&rq->queuelist, &cfqq->fifo);
cfq_add_rq_rb(rq);
cfq_blkiocg_update_io_add_stats(&(RQ_CFQG(rq))->blkg,
&cfqd->serving_group->blkg, rq_data_dir(rq),
rq_is_sync(rq));
cfq_rq_enqueued(cfqd, cfqq, rq);
}
/*
* Update hw_tag based on peak queue depth over 50 samples under
* sufficient load.
*/
static void cfq_update_hw_tag(struct cfq_data *cfqd)
{
struct cfq_queue *cfqq = cfqd->active_queue;
if (cfqd->rq_in_driver > cfqd->hw_tag_est_depth)
cfqd->hw_tag_est_depth = cfqd->rq_in_driver;
if (cfqd->hw_tag == 1)
return;
if (cfqd->rq_queued <= CFQ_HW_QUEUE_MIN &&
cfqd->rq_in_driver <= CFQ_HW_QUEUE_MIN)
return;
/*
* If active queue hasn't enough requests and can idle, cfq might not
* dispatch sufficient requests to hardware. Don't zero hw_tag in this
* case
*/
if (cfqq && cfq_cfqq_idle_window(cfqq) &&
cfqq->dispatched + cfqq->queued[0] + cfqq->queued[1] <
CFQ_HW_QUEUE_MIN && cfqd->rq_in_driver < CFQ_HW_QUEUE_MIN)
return;
if (cfqd->hw_tag_samples++ < 50)
return;
if (cfqd->hw_tag_est_depth >= CFQ_HW_QUEUE_MIN)
cfqd->hw_tag = 1;
else
cfqd->hw_tag = 0;
}
static bool cfq_should_wait_busy(struct cfq_data *cfqd, struct cfq_queue *cfqq)
{
struct cfq_io_context *cic = cfqd->active_cic;
/* If the queue already has requests, don't wait */
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
return false;
/* If there are other queues in the group, don't wait */
if (cfqq->cfqg->nr_cfqq > 1)
return false;
if (cfq_slice_used(cfqq))
return true;
/* if slice left is less than think time, wait busy */
if (cic && sample_valid(cic->ttime_samples)
&& (cfqq->slice_end - jiffies < cic->ttime_mean))
return true;
/*
* If think times is less than a jiffy than ttime_mean=0 and above
* will not be true. It might happen that slice has not expired yet
* but will expire soon (4-5 ns) during select_queue(). To cover the
* case where think time is less than a jiffy, mark the queue wait
* busy if only 1 jiffy is left in the slice.
*/
if (cfqq->slice_end - jiffies == 1)
return true;
return false;
}
static void cfq_completed_request(struct request_queue *q, struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
struct cfq_data *cfqd = cfqq->cfqd;
const int sync = rq_is_sync(rq);
unsigned long now;
now = jiffies;
cfq_log_cfqq(cfqd, cfqq, "complete rqnoidle %d",
!!(rq->cmd_flags & REQ_NOIDLE));
cfq_update_hw_tag(cfqd);
WARN_ON(!cfqd->rq_in_driver);
WARN_ON(!cfqq->dispatched);
cfqd->rq_in_driver--;
cfqq->dispatched--;
(RQ_CFQG(rq))->dispatched--;
cfq_blkiocg_update_completion_stats(&cfqq->cfqg->blkg,
rq_start_time_ns(rq), rq_io_start_time_ns(rq),
rq_data_dir(rq), rq_is_sync(rq));
cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;
if (sync) {
RQ_CIC(rq)->last_end_request = now;
if (!time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
cfqd->last_delayed_sync = now;
}
/*
* If this is the active queue, check if it needs to be expired,
* or if we want to idle in case it has no pending requests.
*/
if (cfqd->active_queue == cfqq) {
const bool cfqq_empty = RB_EMPTY_ROOT(&cfqq->sort_list);
if (cfq_cfqq_slice_new(cfqq)) {
cfq_set_prio_slice(cfqd, cfqq);
cfq_clear_cfqq_slice_new(cfqq);
}
/*
* Should we wait for next request to come in before we expire
* the queue.
*/
if (cfq_should_wait_busy(cfqd, cfqq)) {
unsigned long extend_sl = cfqd->cfq_slice_idle;
if (!cfqd->cfq_slice_idle)
extend_sl = cfqd->cfq_group_idle;
cfqq->slice_end = jiffies + extend_sl;
cfq_mark_cfqq_wait_busy(cfqq);
cfq_log_cfqq(cfqd, cfqq, "will busy wait");
}
/*
* Idling is not enabled on:
* - expired queues
* - idle-priority queues
* - async queues
* - queues with still some requests queued
* - when there is a close cooperator
*/
if (cfq_slice_used(cfqq) || cfq_class_idle(cfqq))
cfq_slice_expired(cfqd, 1);
else if (sync && cfqq_empty &&
!cfq_close_cooperator(cfqd, cfqq)) {
cfq_arm_slice_timer(cfqd);
}
}
if (!cfqd->rq_in_driver)
cfq_schedule_dispatch(cfqd);
}
/*
* we temporarily boost lower priority queues if they are holding fs exclusive
* resources. they are boosted to normal prio (CLASS_BE/4)
*/
static void cfq_prio_boost(struct cfq_queue *cfqq)
{
if (has_fs_excl()) {
/*
* boost idle prio on transactions that would lock out other
* users of the filesystem
*/
if (cfq_class_idle(cfqq))
cfqq->ioprio_class = IOPRIO_CLASS_BE;
if (cfqq->ioprio > IOPRIO_NORM)
cfqq->ioprio = IOPRIO_NORM;
} else {
/*
* unboost the queue (if needed)
*/
cfqq->ioprio_class = cfqq->org_ioprio_class;
cfqq->ioprio = cfqq->org_ioprio;
}
}
static inline int __cfq_may_queue(struct cfq_queue *cfqq)
{
if (cfq_cfqq_wait_request(cfqq) && !cfq_cfqq_must_alloc_slice(cfqq)) {
cfq_mark_cfqq_must_alloc_slice(cfqq);
return ELV_MQUEUE_MUST;
}
return ELV_MQUEUE_MAY;
}
static int cfq_may_queue(struct request_queue *q, int rw)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct task_struct *tsk = current;
struct cfq_io_context *cic;
struct cfq_queue *cfqq;
/*
* don't force setup of a queue from here, as a call to may_queue
* does not necessarily imply that a request actually will be queued.
* so just lookup a possibly existing queue, or return 'may queue'
* if that fails
*/
cic = cfq_cic_lookup(cfqd, tsk->io_context);
if (!cic)
return ELV_MQUEUE_MAY;
cfqq = cic_to_cfqq(cic, rw_is_sync(rw));
if (cfqq) {
cfq_init_prio_data(cfqq, cic->ioc);
cfq_prio_boost(cfqq);
return __cfq_may_queue(cfqq);
}
return ELV_MQUEUE_MAY;
}
/*
* queue lock held here
*/
static void cfq_put_request(struct request *rq)
{
struct cfq_queue *cfqq = RQ_CFQQ(rq);
if (cfqq) {
const int rw = rq_data_dir(rq);
BUG_ON(!cfqq->allocated[rw]);
cfqq->allocated[rw]--;
put_io_context(RQ_CIC(rq)->ioc);
rq->elevator_private[0] = NULL;
rq->elevator_private[1] = NULL;
/* Put down rq reference on cfqg */
cfq_put_cfqg(RQ_CFQG(rq));
rq->elevator_private[2] = NULL;
cfq_put_queue(cfqq);
}
}
static struct cfq_queue *
cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
struct cfq_queue *cfqq)
{
cfq_log_cfqq(cfqd, cfqq, "merging with queue %p", cfqq->new_cfqq);
cic_set_cfqq(cic, cfqq->new_cfqq, 1);
cfq_mark_cfqq_coop(cfqq->new_cfqq);
cfq_put_queue(cfqq);
return cic_to_cfqq(cic, 1);
}
/*
* Returns NULL if a new cfqq should be allocated, or the old cfqq if this
* was the last process referring to said cfqq.
*/
static struct cfq_queue *
split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
{
if (cfqq_process_refs(cfqq) == 1) {
cfqq->pid = current->pid;
cfq_clear_cfqq_coop(cfqq);
cfq_clear_cfqq_split_coop(cfqq);
return cfqq;
}
cic_set_cfqq(cic, NULL, 1);
cfq_put_cooperator(cfqq);
cfq_put_queue(cfqq);
return NULL;
}
/*
* Allocate cfq data structures associated with this request.
*/
static int
cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
{
struct cfq_data *cfqd = q->elevator->elevator_data;
struct cfq_io_context *cic;
const int rw = rq_data_dir(rq);
const bool is_sync = rq_is_sync(rq);
struct cfq_queue *cfqq;
unsigned long flags;
might_sleep_if(gfp_mask & __GFP_WAIT);
cic = cfq_get_io_context(cfqd, gfp_mask);
spin_lock_irqsave(q->queue_lock, flags);
if (!cic)
goto queue_fail;
new_queue:
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
cic_set_cfqq(cic, cfqq, is_sync);
} else {
/*
* If the queue was seeky for too long, break it apart.
*/
if (cfq_cfqq_coop(cfqq) && cfq_cfqq_split_coop(cfqq)) {
cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
cfqq = split_cfqq(cic, cfqq);
if (!cfqq)
goto new_queue;
}
/*
* Check to see if this queue is scheduled to merge with
* another, closely cooperating queue. The merging of
* queues happens here as it must be done in process context.
* The reference on new_cfqq was taken in merge_cfqqs.
*/
if (cfqq->new_cfqq)
cfqq = cfq_merge_cfqqs(cfqd, cic, cfqq);
}
cfqq->allocated[rw]++;
cfqq->ref++;
rq->elevator_private[0] = cic;
rq->elevator_private[1] = cfqq;
rq->elevator_private[2] = cfq_ref_get_cfqg(cfqq->cfqg);
spin_unlock_irqrestore(q->queue_lock, flags);
return 0;
queue_fail:
if (cic)
put_io_context(cic->ioc);
cfq_schedule_dispatch(cfqd);
spin_unlock_irqrestore(q->queue_lock, flags);
cfq_log(cfqd, "set_request fail");
return 1;
}
static void cfq_kick_queue(struct work_struct *work)
{
struct cfq_data *cfqd =
container_of(work, struct cfq_data, unplug_work);
struct request_queue *q = cfqd->queue;
spin_lock_irq(q->queue_lock);
__blk_run_queue(cfqd->queue);
spin_unlock_irq(q->queue_lock);
}
/*
* Timer running if the active_queue is currently idling inside its time slice
*/
static void cfq_idle_slice_timer(unsigned long data)
{
struct cfq_data *cfqd = (struct cfq_data *) data;
struct cfq_queue *cfqq;
unsigned long flags;
int timed_out = 1;
cfq_log(cfqd, "idle timer fired");
spin_lock_irqsave(cfqd->queue->queue_lock, flags);
cfqq = cfqd->active_queue;
if (cfqq) {
timed_out = 0;
/*
* We saw a request before the queue expired, let it through
*/
if (cfq_cfqq_must_dispatch(cfqq))
goto out_kick;
/*
* expired
*/
if (cfq_slice_used(cfqq))
goto expire;
/*
* only expire and reinvoke request handler, if there are
* other queues with pending requests
*/
if (!cfqd->busy_queues)
goto out_cont;
/*
* not expired and it has a request pending, let it dispatch
*/
if (!RB_EMPTY_ROOT(&cfqq->sort_list))
goto out_kick;
/*
* Queue depth flag is reset only when the idle didn't succeed
*/
cfq_clear_cfqq_deep(cfqq);
}
expire:
cfq_slice_expired(cfqd, timed_out);
out_kick:
cfq_schedule_dispatch(cfqd);
out_cont:
spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);
}
static void cfq_shutdown_timer_wq(struct cfq_data *cfqd)
{
del_timer_sync(&cfqd->idle_slice_timer);
cancel_work_sync(&cfqd->unplug_work);
}
static void cfq_put_async_queues(struct cfq_data *cfqd)
{
int i;
for (i = 0; i < IOPRIO_BE_NR; i++) {
if (cfqd->async_cfqq[0][i])
cfq_put_queue(cfqd->async_cfqq[0][i]);
if (cfqd->async_cfqq[1][i])
cfq_put_queue(cfqd->async_cfqq[1][i]);
}
if (cfqd->async_idle_cfqq)
cfq_put_queue(cfqd->async_idle_cfqq);
}
static void cfq_cfqd_free(struct rcu_head *head)
{
kfree(container_of(head, struct cfq_data, rcu));
}
static void cfq_exit_queue(struct elevator_queue *e)
{
struct cfq_data *cfqd = e->elevator_data;
struct request_queue *q = cfqd->queue;
cfq_shutdown_timer_wq(cfqd);
spin_lock_irq(q->queue_lock);
if (cfqd->active_queue)
__cfq_slice_expired(cfqd, cfqd->active_queue, 0);
while (!list_empty(&cfqd->cic_list)) {
struct cfq_io_context *cic = list_entry(cfqd->cic_list.next,
struct cfq_io_context,
queue_list);
__cfq_exit_single_io_context(cfqd, cic);
}
cfq_put_async_queues(cfqd);
cfq_release_cfq_groups(cfqd);
cfq_blkiocg_del_blkio_group(&cfqd->root_group.blkg);
spin_unlock_irq(q->queue_lock);
cfq_shutdown_timer_wq(cfqd);
spin_lock(&cic_index_lock);
ida_remove(&cic_index_ida, cfqd->cic_index);
spin_unlock(&cic_index_lock);
/* Wait for cfqg->blkg->key accessors to exit their grace periods. */
call_rcu(&cfqd->rcu, cfq_cfqd_free);
}
static int cfq_alloc_cic_index(void)
{
int index, error;
do {
if (!ida_pre_get(&cic_index_ida, GFP_KERNEL))
return -ENOMEM;
spin_lock(&cic_index_lock);
error = ida_get_new(&cic_index_ida, &index);
spin_unlock(&cic_index_lock);
if (error && error != -EAGAIN)
return error;
} while (error);
return index;
}
static void *cfq_init_queue(struct request_queue *q)
{
struct cfq_data *cfqd;
int i, j;
struct cfq_group *cfqg;
struct cfq_rb_root *st;
i = cfq_alloc_cic_index();
if (i < 0)
return NULL;
cfqd = kmalloc_node(sizeof(*cfqd), GFP_KERNEL | __GFP_ZERO, q->node);
if (!cfqd)
return NULL;
/*
* Don't need take queue_lock in the routine, since we are
* initializing the ioscheduler, and nobody is using cfqd
*/
cfqd->cic_index = i;
/* Init root service tree */
cfqd->grp_service_tree = CFQ_RB_ROOT;
/* Init root group */
cfqg = &cfqd->root_group;
for_each_cfqg_st(cfqg, i, j, st)
*st = CFQ_RB_ROOT;
RB_CLEAR_NODE(&cfqg->rb_node);
/* Give preference to root group over other groups */
cfqg->weight = 2*BLKIO_WEIGHT_DEFAULT;
#ifdef CONFIG_CFQ_GROUP_IOSCHED
/*
* Take a reference to root group which we never drop. This is just
* to make sure that cfq_put_cfqg() does not try to kfree root group
*/
cfqg->ref = 1;
rcu_read_lock();
cfq_blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg,
(void *)cfqd, 0);
rcu_read_unlock();
#endif
/*
* Not strictly needed (since RB_ROOT just clears the node and we
* zeroed cfqd on alloc), but better be safe in case someone decides
* to add magic to the rb code
*/
for (i = 0; i < CFQ_PRIO_LISTS; i++)
cfqd->prio_trees[i] = RB_ROOT;
/*
* Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
* Grab a permanent reference to it, so that the normal code flow
* will not attempt to free it.
*/
cfq_init_cfqq(cfqd, &cfqd->oom_cfqq, 1, 0);
cfqd->oom_cfqq.ref++;
cfq_link_cfqq_cfqg(&cfqd->oom_cfqq, &cfqd->root_group);
INIT_LIST_HEAD(&cfqd->cic_list);
cfqd->queue = q;
init_timer(&cfqd->idle_slice_timer);
cfqd->idle_slice_timer.function = cfq_idle_slice_timer;
cfqd->idle_slice_timer.data = (unsigned long) cfqd;
INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
cfqd->cfq_quantum = cfq_quantum;
cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];
cfqd->cfq_back_max = cfq_back_max;
cfqd->cfq_back_penalty = cfq_back_penalty;
cfqd->cfq_slice[0] = cfq_slice_async;
cfqd->cfq_slice[1] = cfq_slice_sync;
cfqd->cfq_slice_async_rq = cfq_slice_async_rq;
cfqd->cfq_slice_idle = cfq_slice_idle;
cfqd->cfq_group_idle = cfq_group_idle;
cfqd->cfq_latency = 1;
cfqd->hw_tag = -1;
/*
* we optimistically start assuming sync ops weren't delayed in last
* second, in order to have larger depth for async operations.
*/
cfqd->last_delayed_sync = jiffies - HZ;
return cfqd;
}
static void cfq_slab_kill(void)
{
/*
* Caller already ensured that pending RCU callbacks are completed,
* so we should have no busy allocations at this point.
*/
if (cfq_pool)
kmem_cache_destroy(cfq_pool);
if (cfq_ioc_pool)
kmem_cache_destroy(cfq_ioc_pool);
}
static int __init cfq_slab_setup(void)
{
cfq_pool = KMEM_CACHE(cfq_queue, 0);
if (!cfq_pool)
goto fail;
cfq_ioc_pool = KMEM_CACHE(cfq_io_context, 0);
if (!cfq_ioc_pool)
goto fail;
return 0;
fail:
cfq_slab_kill();
return -ENOMEM;
}
/*
* sysfs parts below -->
*/
static ssize_t
cfq_var_show(unsigned int var, char *page)
{
return sprintf(page, "%d\n", var);
}
static ssize_t
cfq_var_store(unsigned int *var, const char *page, size_t count)
{
char *p = (char *) page;
*var = simple_strtoul(p, &p, 10);
return count;
}
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data = __VAR; \
if (__CONV) \
__data = jiffies_to_msecs(__data); \
return cfq_var_show(__data, (page)); \
}
SHOW_FUNCTION(cfq_quantum_show, cfqd->cfq_quantum, 0);
SHOW_FUNCTION(cfq_fifo_expire_sync_show, cfqd->cfq_fifo_expire[1], 1);
SHOW_FUNCTION(cfq_fifo_expire_async_show, cfqd->cfq_fifo_expire[0], 1);
SHOW_FUNCTION(cfq_back_seek_max_show, cfqd->cfq_back_max, 0);
SHOW_FUNCTION(cfq_back_seek_penalty_show, cfqd->cfq_back_penalty, 0);
SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1);
SHOW_FUNCTION(cfq_group_idle_show, cfqd->cfq_group_idle, 1);
SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1);
SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1);
SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0);
SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0);
#undef SHOW_FUNCTION
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
{ \
struct cfq_data *cfqd = e->elevator_data; \
unsigned int __data; \
int ret = cfq_var_store(&__data, (page), count); \
if (__data < (MIN)) \
__data = (MIN); \
else if (__data > (MAX)) \
__data = (MAX); \
if (__CONV) \
*(__PTR) = msecs_to_jiffies(__data); \
else \
*(__PTR) = __data; \
return ret; \
}
STORE_FUNCTION(cfq_quantum_store, &cfqd->cfq_quantum, 1, UINT_MAX, 0);
STORE_FUNCTION(cfq_fifo_expire_sync_store, &cfqd->cfq_fifo_expire[1], 1,
UINT_MAX, 1);
STORE_FUNCTION(cfq_fifo_expire_async_store, &cfqd->cfq_fifo_expire[0], 1,
UINT_MAX, 1);
STORE_FUNCTION(cfq_back_seek_max_store, &cfqd->cfq_back_max, 0, UINT_MAX, 0);
STORE_FUNCTION(cfq_back_seek_penalty_store, &cfqd->cfq_back_penalty, 1,
UINT_MAX, 0);
STORE_FUNCTION(cfq_slice_idle_store, &cfqd->cfq_slice_idle, 0, UINT_MAX, 1);
STORE_FUNCTION(cfq_group_idle_store, &cfqd->cfq_group_idle, 0, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1);
STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1,
UINT_MAX, 0);
STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0);
#undef STORE_FUNCTION
#define CFQ_ATTR(name) \
__ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
static struct elv_fs_entry cfq_attrs[] = {
CFQ_ATTR(quantum),
CFQ_ATTR(fifo_expire_sync),
CFQ_ATTR(fifo_expire_async),
CFQ_ATTR(back_seek_max),
CFQ_ATTR(back_seek_penalty),
CFQ_ATTR(slice_sync),
CFQ_ATTR(slice_async),
CFQ_ATTR(slice_async_rq),
CFQ_ATTR(slice_idle),
CFQ_ATTR(group_idle),
CFQ_ATTR(low_latency),
__ATTR_NULL
};
static struct elevator_type iosched_cfq = {
.ops = {
.elevator_merge_fn = cfq_merge,
.elevator_merged_fn = cfq_merged_request,
.elevator_merge_req_fn = cfq_merged_requests,
.elevator_allow_merge_fn = cfq_allow_merge,
.elevator_bio_merged_fn = cfq_bio_merged,
.elevator_dispatch_fn = cfq_dispatch_requests,
.elevator_add_req_fn = cfq_insert_request,
.elevator_activate_req_fn = cfq_activate_request,
.elevator_deactivate_req_fn = cfq_deactivate_request,
.elevator_completed_req_fn = cfq_completed_request,
.elevator_former_req_fn = elv_rb_former_request,
.elevator_latter_req_fn = elv_rb_latter_request,
.elevator_set_req_fn = cfq_set_request,
.elevator_put_req_fn = cfq_put_request,
.elevator_may_queue_fn = cfq_may_queue,
.elevator_init_fn = cfq_init_queue,
.elevator_exit_fn = cfq_exit_queue,
.trim = cfq_free_io_context,
},
.elevator_attrs = cfq_attrs,
.elevator_name = "cfq",
.elevator_owner = THIS_MODULE,
};
#ifdef CONFIG_CFQ_GROUP_IOSCHED
static struct blkio_policy_type blkio_policy_cfq = {
.ops = {
.blkio_unlink_group_fn = cfq_unlink_blkio_group,
.blkio_update_group_weight_fn = cfq_update_blkio_group_weight,
},
.plid = BLKIO_POLICY_PROP,
};
#else
static struct blkio_policy_type blkio_policy_cfq;
#endif
static int __init cfq_init(void)
{
/*
* could be 0 on HZ < 1000 setups
*/
if (!cfq_slice_async)
cfq_slice_async = 1;
if (!cfq_slice_idle)
cfq_slice_idle = 1;
#ifdef CONFIG_CFQ_GROUP_IOSCHED
if (!cfq_group_idle)
cfq_group_idle = 1;
#else
cfq_group_idle = 0;
#endif
if (cfq_slab_setup())
return -ENOMEM;
elv_register(&iosched_cfq);
blkio_policy_register(&blkio_policy_cfq);
return 0;
}
static void __exit cfq_exit(void)
{
DECLARE_COMPLETION_ONSTACK(all_gone);
blkio_policy_unregister(&blkio_policy_cfq);
elv_unregister(&iosched_cfq);
ioc_gone = &all_gone;
/* ioc_gone's update must be visible before reading ioc_count */
smp_wmb();
/*
* this also protects us from entering cfq_slab_kill() with
* pending RCU callbacks
*/
if (elv_ioc_count_read(cfq_ioc_count))
wait_for_completion(&all_gone);
ida_destroy(&cic_index_ida);
cfq_slab_kill();
}
module_init(cfq_init);
module_exit(cfq_exit);
MODULE_AUTHOR("Jens Axboe");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");
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