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kernel-fxtec-pro1x/mm/mmap.c
Davidlohr Bueso 615d6e8756 mm: per-thread vma caching 
This patch is a continuation of efforts trying to optimize find_vma(),
avoiding potentially expensive rbtree walks to locate a vma upon faults.
The original approach (https://lkml.org/lkml/2013/11/1/410), where the
largest vma was also cached, ended up being too specific and random,
thus further comparison with other approaches were needed.  There are
two things to consider when dealing with this, the cache hit rate and
the latency of find_vma().  Improving the hit-rate does not necessarily
translate in finding the vma any faster, as the overhead of any fancy
caching schemes can be too high to consider.

We currently cache the last used vma for the whole address space, which
provides a nice optimization, reducing the total cycles in find_vma() by
up to 250%, for workloads with good locality.  On the other hand, this
simple scheme is pretty much useless for workloads with poor locality.
Analyzing ebizzy runs shows that, no matter how many threads are
running, the mmap_cache hit rate is less than 2%, and in many situations
below 1%.

The proposed approach is to replace this scheme with a small per-thread
cache, maximizing hit rates at a very low maintenance cost.
Invalidations are performed by simply bumping up a 32-bit sequence
number.  The only expensive operation is in the rare case of a seq
number overflow, where all caches that share the same address space are
flushed.  Upon a miss, the proposed replacement policy is based on the
page number that contains the virtual address in question.  Concretely,
the following results are seen on an 80 core, 8 socket x86-64 box:

1) System bootup: Most programs are single threaded, so the per-thread
   scheme does improve ~50% hit rate by just adding a few more slots to
   the cache.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 50.61%   | 19.90            |
| patched        | 73.45%   | 13.58            |
+----------------+----------+------------------+

2) Kernel build: This one is already pretty good with the current
   approach as we're dealing with good locality.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 75.28%   | 11.03            |
| patched        | 88.09%   | 9.31             |
+----------------+----------+------------------+

3) Oracle 11g Data Mining (4k pages): Similar to the kernel build workload.

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 70.66%   | 17.14            |
| patched        | 91.15%   | 12.57            |
+----------------+----------+------------------+

4) Ebizzy: There's a fair amount of variation from run to run, but this
   approach always shows nearly perfect hit rates, while baseline is just
   about non-existent.  The amounts of cycles can fluctuate between
   anywhere from ~60 to ~116 for the baseline scheme, but this approach
   reduces it considerably.  For instance, with 80 threads:

+----------------+----------+------------------+
| caching scheme | hit-rate | cycles (billion) |
+----------------+----------+------------------+
| baseline       | 1.06%    | 91.54            |
| patched        | 99.97%   | 14.18            |
+----------------+----------+------------------+

[akpm@linux-foundation.org: fix nommu build, per Davidlohr]
[akpm@linux-foundation.org: document vmacache_valid() logic]
[akpm@linux-foundation.org: attempt to untangle header files]
[akpm@linux-foundation.org: add vmacache_find() BUG_ON]
[hughd@google.com: add vmacache_valid_mm() (from Oleg)]
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: adjust and enhance comments]
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Michel Lespinasse <walken@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Tested-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07 16:35:53 -07:00

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/*
* mm/mmap.c
*
* Written by obz.
*
* Address space accounting code <alan@lxorguk.ukuu.org.uk>
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/backing-dev.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
#include <linux/shm.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/capability.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/hugetlb.h>
#include <linux/profile.h>
#include <linux/export.h>
#include <linux/mount.h>
#include <linux/mempolicy.h>
#include <linux/rmap.h>
#include <linux/mmu_notifier.h>
#include <linux/perf_event.h>
#include <linux/audit.h>
#include <linux/khugepaged.h>
#include <linux/uprobes.h>
#include <linux/rbtree_augmented.h>
#include <linux/sched/sysctl.h>
#include <linux/notifier.h>
#include <linux/memory.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/tlb.h>
#include <asm/mmu_context.h>
#include "internal.h"
#ifndef arch_mmap_check
#define arch_mmap_check(addr, len, flags) (0)
#endif
#ifndef arch_rebalance_pgtables
#define arch_rebalance_pgtables(addr, len) (addr)
#endif
static void unmap_region(struct mm_struct *mm,
struct vm_area_struct *vma, struct vm_area_struct *prev,
unsigned long start, unsigned long end);
/* description of effects of mapping type and prot in current implementation.
* this is due to the limited x86 page protection hardware. The expected
* behavior is in parens:
*
* map_type prot
* PROT_NONE PROT_READ PROT_WRITE PROT_EXEC
* MAP_SHARED r: (no) no r: (yes) yes r: (no) yes r: (no) yes
* w: (no) no w: (no) no w: (yes) yes w: (no) no
* x: (no) no x: (no) yes x: (no) yes x: (yes) yes
*
* MAP_PRIVATE r: (no) no r: (yes) yes r: (no) yes r: (no) yes
* w: (no) no w: (no) no w: (copy) copy w: (no) no
* x: (no) no x: (no) yes x: (no) yes x: (yes) yes
*
*/
pgprot_t protection_map[16] = {
__P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
__S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
};
pgprot_t vm_get_page_prot(unsigned long vm_flags)
{
return __pgprot(pgprot_val(protection_map[vm_flags &
(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
pgprot_val(arch_vm_get_page_prot(vm_flags)));
}
EXPORT_SYMBOL(vm_get_page_prot);
int sysctl_overcommit_memory __read_mostly = OVERCOMMIT_GUESS; /* heuristic overcommit */
int sysctl_overcommit_ratio __read_mostly = 50; /* default is 50% */
unsigned long sysctl_overcommit_kbytes __read_mostly;
int sysctl_max_map_count __read_mostly = DEFAULT_MAX_MAP_COUNT;
unsigned long sysctl_user_reserve_kbytes __read_mostly = 1UL << 17; /* 128MB */
unsigned long sysctl_admin_reserve_kbytes __read_mostly = 1UL << 13; /* 8MB */
/*
* Make sure vm_committed_as in one cacheline and not cacheline shared with
* other variables. It can be updated by several CPUs frequently.
*/
struct percpu_counter vm_committed_as ____cacheline_aligned_in_smp;
/*
* The global memory commitment made in the system can be a metric
* that can be used to drive ballooning decisions when Linux is hosted
* as a guest. On Hyper-V, the host implements a policy engine for dynamically
* balancing memory across competing virtual machines that are hosted.
* Several metrics drive this policy engine including the guest reported
* memory commitment.
*/
unsigned long vm_memory_committed(void)
{
return percpu_counter_read_positive(&vm_committed_as);
}
EXPORT_SYMBOL_GPL(vm_memory_committed);
/*
* Check that a process has enough memory to allocate a new virtual
* mapping. 0 means there is enough memory for the allocation to
* succeed and -ENOMEM implies there is not.
*
* We currently support three overcommit policies, which are set via the
* vm.overcommit_memory sysctl. See Documentation/vm/overcommit-accounting
*
* Strict overcommit modes added 2002 Feb 26 by Alan Cox.
* Additional code 2002 Jul 20 by Robert Love.
*
* cap_sys_admin is 1 if the process has admin privileges, 0 otherwise.
*
* Note this is a helper function intended to be used by LSMs which
* wish to use this logic.
*/
int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
{
unsigned long free, allowed, reserve;
vm_acct_memory(pages);
/*
* Sometimes we want to use more memory than we have
*/
if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
return 0;
if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
free = global_page_state(NR_FREE_PAGES);
free += global_page_state(NR_FILE_PAGES);
/*
* shmem pages shouldn't be counted as free in this
* case, they can't be purged, only swapped out, and
* that won't affect the overall amount of available
* memory in the system.
*/
free -= global_page_state(NR_SHMEM);
free += get_nr_swap_pages();
/*
* Any slabs which are created with the
* SLAB_RECLAIM_ACCOUNT flag claim to have contents
* which are reclaimable, under pressure. The dentry
* cache and most inode caches should fall into this
*/
free += global_page_state(NR_SLAB_RECLAIMABLE);
/*
* Leave reserved pages. The pages are not for anonymous pages.
*/
if (free <= totalreserve_pages)
goto error;
else
free -= totalreserve_pages;
/*
* Reserve some for root
*/
if (!cap_sys_admin)
free -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
if (free > pages)
return 0;
goto error;
}
allowed = vm_commit_limit();
/*
* Reserve some for root
*/
if (!cap_sys_admin)
allowed -= sysctl_admin_reserve_kbytes >> (PAGE_SHIFT - 10);
/*
* Don't let a single process grow so big a user can't recover
*/
if (mm) {
reserve = sysctl_user_reserve_kbytes >> (PAGE_SHIFT - 10);
allowed -= min(mm->total_vm / 32, reserve);
}
if (percpu_counter_read_positive(&vm_committed_as) < allowed)
return 0;
error:
vm_unacct_memory(pages);
return -ENOMEM;
}
/*
* Requires inode->i_mapping->i_mmap_mutex
*/
static void __remove_shared_vm_struct(struct vm_area_struct *vma,
struct file *file, struct address_space *mapping)
{
if (vma->vm_flags & VM_DENYWRITE)
atomic_inc(&file_inode(file)->i_writecount);
if (vma->vm_flags & VM_SHARED)
mapping->i_mmap_writable--;
flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
list_del_init(&vma->shared.nonlinear);
else
vma_interval_tree_remove(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
/*
* Unlink a file-based vm structure from its interval tree, to hide
* vma from rmap and vmtruncate before freeing its page tables.
*/
void unlink_file_vma(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
if (file) {
struct address_space *mapping = file->f_mapping;
mutex_lock(&mapping->i_mmap_mutex);
__remove_shared_vm_struct(vma, file, mapping);
mutex_unlock(&mapping->i_mmap_mutex);
}
}
/*
* Close a vm structure and free it, returning the next.
*/
static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
{
struct vm_area_struct *next = vma->vm_next;
might_sleep();
if (vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file)
fput(vma->vm_file);
mpol_put(vma_policy(vma));
kmem_cache_free(vm_area_cachep, vma);
return next;
}
static unsigned long do_brk(unsigned long addr, unsigned long len);
SYSCALL_DEFINE1(brk, unsigned long, brk)
{
unsigned long rlim, retval;
unsigned long newbrk, oldbrk;
struct mm_struct *mm = current->mm;
unsigned long min_brk;
bool populate;
down_write(&mm->mmap_sem);
#ifdef CONFIG_COMPAT_BRK
/*
* CONFIG_COMPAT_BRK can still be overridden by setting
* randomize_va_space to 2, which will still cause mm->start_brk
* to be arbitrarily shifted
*/
if (current->brk_randomized)
min_brk = mm->start_brk;
else
min_brk = mm->end_data;
#else
min_brk = mm->start_brk;
#endif
if (brk < min_brk)
goto out;
/*
* Check against rlimit here. If this check is done later after the test
* of oldbrk with newbrk then it can escape the test and let the data
* segment grow beyond its set limit the in case where the limit is
* not page aligned -Ram Gupta
*/
rlim = rlimit(RLIMIT_DATA);
if (rlim < RLIM_INFINITY && (brk - mm->start_brk) +
(mm->end_data - mm->start_data) > rlim)
goto out;
newbrk = PAGE_ALIGN(brk);
oldbrk = PAGE_ALIGN(mm->brk);
if (oldbrk == newbrk)
goto set_brk;
/* Always allow shrinking brk. */
if (brk <= mm->brk) {
if (!do_munmap(mm, newbrk, oldbrk-newbrk))
goto set_brk;
goto out;
}
/* Check against existing mmap mappings. */
if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
goto out;
/* Ok, looks good - let it rip. */
if (do_brk(oldbrk, newbrk-oldbrk) != oldbrk)
goto out;
set_brk:
mm->brk = brk;
populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
up_write(&mm->mmap_sem);
if (populate)
mm_populate(oldbrk, newbrk - oldbrk);
return brk;
out:
retval = mm->brk;
up_write(&mm->mmap_sem);
return retval;
}
static long vma_compute_subtree_gap(struct vm_area_struct *vma)
{
unsigned long max, subtree_gap;
max = vma->vm_start;
if (vma->vm_prev)
max -= vma->vm_prev->vm_end;
if (vma->vm_rb.rb_left) {
subtree_gap = rb_entry(vma->vm_rb.rb_left,
struct vm_area_struct, vm_rb)->rb_subtree_gap;
if (subtree_gap > max)
max = subtree_gap;
}
if (vma->vm_rb.rb_right) {
subtree_gap = rb_entry(vma->vm_rb.rb_right,
struct vm_area_struct, vm_rb)->rb_subtree_gap;
if (subtree_gap > max)
max = subtree_gap;
}
return max;
}
#ifdef CONFIG_DEBUG_VM_RB
static int browse_rb(struct rb_root *root)
{
int i = 0, j, bug = 0;
struct rb_node *nd, *pn = NULL;
unsigned long prev = 0, pend = 0;
for (nd = rb_first(root); nd; nd = rb_next(nd)) {
struct vm_area_struct *vma;
vma = rb_entry(nd, struct vm_area_struct, vm_rb);
if (vma->vm_start < prev) {
printk("vm_start %lx prev %lx\n", vma->vm_start, prev);
bug = 1;
}
if (vma->vm_start < pend) {
printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
bug = 1;
}
if (vma->vm_start > vma->vm_end) {
printk("vm_end %lx < vm_start %lx\n",
vma->vm_end, vma->vm_start);
bug = 1;
}
if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
printk("free gap %lx, correct %lx\n",
vma->rb_subtree_gap,
vma_compute_subtree_gap(vma));
bug = 1;
}
i++;
pn = nd;
prev = vma->vm_start;
pend = vma->vm_end;
}
j = 0;
for (nd = pn; nd; nd = rb_prev(nd))
j++;
if (i != j) {
printk("backwards %d, forwards %d\n", j, i);
bug = 1;
}
return bug ? -1 : i;
}
static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
{
struct rb_node *nd;
for (nd = rb_first(root); nd; nd = rb_next(nd)) {
struct vm_area_struct *vma;
vma = rb_entry(nd, struct vm_area_struct, vm_rb);
BUG_ON(vma != ignore &&
vma->rb_subtree_gap != vma_compute_subtree_gap(vma));
}
}
static void validate_mm(struct mm_struct *mm)
{
int bug = 0;
int i = 0;
unsigned long highest_address = 0;
struct vm_area_struct *vma = mm->mmap;
while (vma) {
struct anon_vma_chain *avc;
vma_lock_anon_vma(vma);
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_verify(avc);
vma_unlock_anon_vma(vma);
highest_address = vma->vm_end;
vma = vma->vm_next;
i++;
}
if (i != mm->map_count) {
printk("map_count %d vm_next %d\n", mm->map_count, i);
bug = 1;
}
if (highest_address != mm->highest_vm_end) {
printk("mm->highest_vm_end %lx, found %lx\n",
mm->highest_vm_end, highest_address);
bug = 1;
}
i = browse_rb(&mm->mm_rb);
if (i != mm->map_count) {
printk("map_count %d rb %d\n", mm->map_count, i);
bug = 1;
}
BUG_ON(bug);
}
#else
#define validate_mm_rb(root, ignore) do { } while (0)
#define validate_mm(mm) do { } while (0)
#endif
RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
/*
* Update augmented rbtree rb_subtree_gap values after vma->vm_start or
* vma->vm_prev->vm_end values changed, without modifying the vma's position
* in the rbtree.
*/
static void vma_gap_update(struct vm_area_struct *vma)
{
/*
* As it turns out, RB_DECLARE_CALLBACKS() already created a callback
* function that does exacltly what we want.
*/
vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
}
static inline void vma_rb_insert(struct vm_area_struct *vma,
struct rb_root *root)
{
/* All rb_subtree_gap values must be consistent prior to insertion */
validate_mm_rb(root, NULL);
rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
}
static void vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
{
/*
* All rb_subtree_gap values must be consistent prior to erase,
* with the possible exception of the vma being erased.
*/
validate_mm_rb(root, vma);
/*
* Note rb_erase_augmented is a fairly large inline function,
* so make sure we instantiate it only once with our desired
* augmented rbtree callbacks.
*/
rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
}
/*
* vma has some anon_vma assigned, and is already inserted on that
* anon_vma's interval trees.
*
* Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
* vma must be removed from the anon_vma's interval trees using
* anon_vma_interval_tree_pre_update_vma().
*
* After the update, the vma will be reinserted using
* anon_vma_interval_tree_post_update_vma().
*
* The entire update must be protected by exclusive mmap_sem and by
* the root anon_vma's mutex.
*/
static inline void
anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc;
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
}
static inline void
anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
{
struct anon_vma_chain *avc;
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
}
static int find_vma_links(struct mm_struct *mm, unsigned long addr,
unsigned long end, struct vm_area_struct **pprev,
struct rb_node ***rb_link, struct rb_node **rb_parent)
{
struct rb_node **__rb_link, *__rb_parent, *rb_prev;
__rb_link = &mm->mm_rb.rb_node;
rb_prev = __rb_parent = NULL;
while (*__rb_link) {
struct vm_area_struct *vma_tmp;
__rb_parent = *__rb_link;
vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
if (vma_tmp->vm_end > addr) {
/* Fail if an existing vma overlaps the area */
if (vma_tmp->vm_start < end)
return -ENOMEM;
__rb_link = &__rb_parent->rb_left;
} else {
rb_prev = __rb_parent;
__rb_link = &__rb_parent->rb_right;
}
}
*pprev = NULL;
if (rb_prev)
*pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
*rb_link = __rb_link;
*rb_parent = __rb_parent;
return 0;
}
static unsigned long count_vma_pages_range(struct mm_struct *mm,
unsigned long addr, unsigned long end)
{
unsigned long nr_pages = 0;
struct vm_area_struct *vma;
/* Find first overlaping mapping */
vma = find_vma_intersection(mm, addr, end);
if (!vma)
return 0;
nr_pages = (min(end, vma->vm_end) -
max(addr, vma->vm_start)) >> PAGE_SHIFT;
/* Iterate over the rest of the overlaps */
for (vma = vma->vm_next; vma; vma = vma->vm_next) {
unsigned long overlap_len;
if (vma->vm_start > end)
break;
overlap_len = min(end, vma->vm_end) - vma->vm_start;
nr_pages += overlap_len >> PAGE_SHIFT;
}
return nr_pages;
}
void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
struct rb_node **rb_link, struct rb_node *rb_parent)
{
/* Update tracking information for the gap following the new vma. */
if (vma->vm_next)
vma_gap_update(vma->vm_next);
else
mm->highest_vm_end = vma->vm_end;
/*
* vma->vm_prev wasn't known when we followed the rbtree to find the
* correct insertion point for that vma. As a result, we could not
* update the vma vm_rb parents rb_subtree_gap values on the way down.
* So, we first insert the vma with a zero rb_subtree_gap value
* (to be consistent with what we did on the way down), and then
* immediately update the gap to the correct value. Finally we
* rebalance the rbtree after all augmented values have been set.
*/
rb_link_node(&vma->vm_rb, rb_parent, rb_link);
vma->rb_subtree_gap = 0;
vma_gap_update(vma);
vma_rb_insert(vma, &mm->mm_rb);
}
static void __vma_link_file(struct vm_area_struct *vma)
{
struct file *file;
file = vma->vm_file;
if (file) {
struct address_space *mapping = file->f_mapping;
if (vma->vm_flags & VM_DENYWRITE)
atomic_dec(&file_inode(file)->i_writecount);
if (vma->vm_flags & VM_SHARED)
mapping->i_mmap_writable++;
flush_dcache_mmap_lock(mapping);
if (unlikely(vma->vm_flags & VM_NONLINEAR))
vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
else
vma_interval_tree_insert(vma, &mapping->i_mmap);
flush_dcache_mmap_unlock(mapping);
}
}
static void
__vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct rb_node **rb_link,
struct rb_node *rb_parent)
{
__vma_link_list(mm, vma, prev, rb_parent);
__vma_link_rb(mm, vma, rb_link, rb_parent);
}
static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct rb_node **rb_link,
struct rb_node *rb_parent)
{
struct address_space *mapping = NULL;
if (vma->vm_file)
mapping = vma->vm_file->f_mapping;
if (mapping)
mutex_lock(&mapping->i_mmap_mutex);
__vma_link(mm, vma, prev, rb_link, rb_parent);
__vma_link_file(vma);
if (mapping)
mutex_unlock(&mapping->i_mmap_mutex);
mm->map_count++;
validate_mm(mm);
}
/*
* Helper for vma_adjust() in the split_vma insert case: insert a vma into the
* mm's list and rbtree. It has already been inserted into the interval tree.
*/
static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
struct vm_area_struct *prev;
struct rb_node **rb_link, *rb_parent;
if (find_vma_links(mm, vma->vm_start, vma->vm_end,
&prev, &rb_link, &rb_parent))
BUG();
__vma_link(mm, vma, prev, rb_link, rb_parent);
mm->map_count++;
}
static inline void
__vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev)
{
struct vm_area_struct *next;
vma_rb_erase(vma, &mm->mm_rb);
prev->vm_next = next = vma->vm_next;
if (next)
next->vm_prev = prev;
/* Kill the cache */
vmacache_invalidate(mm);
}
/*
* We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
* is already present in an i_mmap tree without adjusting the tree.
* The following helper function should be used when such adjustments
* are necessary. The "insert" vma (if any) is to be inserted
* before we drop the necessary locks.
*/
int vma_adjust(struct vm_area_struct *vma, unsigned long start,
unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert)
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *next = vma->vm_next;
struct vm_area_struct *importer = NULL;
struct address_space *mapping = NULL;
struct rb_root *root = NULL;
struct anon_vma *anon_vma = NULL;
struct file *file = vma->vm_file;
bool start_changed = false, end_changed = false;
long adjust_next = 0;
int remove_next = 0;
if (next && !insert) {
struct vm_area_struct *exporter = NULL;
if (end >= next->vm_end) {
/*
* vma expands, overlapping all the next, and
* perhaps the one after too (mprotect case 6).
*/
again: remove_next = 1 + (end > next->vm_end);
end = next->vm_end;
exporter = next;
importer = vma;
} else if (end > next->vm_start) {
/*
* vma expands, overlapping part of the next:
* mprotect case 5 shifting the boundary up.
*/
adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
exporter = next;
importer = vma;
} else if (end < vma->vm_end) {
/*
* vma shrinks, and !insert tells it's not
* split_vma inserting another: so it must be
* mprotect case 4 shifting the boundary down.
*/
adjust_next = - ((vma->vm_end - end) >> PAGE_SHIFT);
exporter = vma;
importer = next;
}
/*
* Easily overlooked: when mprotect shifts the boundary,
* make sure the expanding vma has anon_vma set if the
* shrinking vma had, to cover any anon pages imported.
*/
if (exporter && exporter->anon_vma && !importer->anon_vma) {
if (anon_vma_clone(importer, exporter))
return -ENOMEM;
importer->anon_vma = exporter->anon_vma;
}
}
if (file) {
mapping = file->f_mapping;
if (!(vma->vm_flags & VM_NONLINEAR)) {
root = &mapping->i_mmap;
uprobe_munmap(vma, vma->vm_start, vma->vm_end);
if (adjust_next)
uprobe_munmap(next, next->vm_start,
next->vm_end);
}
mutex_lock(&mapping->i_mmap_mutex);
if (insert) {
/*
* Put into interval tree now, so instantiated pages
* are visible to arm/parisc __flush_dcache_page
* throughout; but we cannot insert into address
* space until vma start or end is updated.
*/
__vma_link_file(insert);
}
}
vma_adjust_trans_huge(vma, start, end, adjust_next);
anon_vma = vma->anon_vma;
if (!anon_vma && adjust_next)
anon_vma = next->anon_vma;
if (anon_vma) {
VM_BUG_ON(adjust_next && next->anon_vma &&
anon_vma != next->anon_vma);
anon_vma_lock_write(anon_vma);
anon_vma_interval_tree_pre_update_vma(vma);
if (adjust_next)
anon_vma_interval_tree_pre_update_vma(next);
}
if (root) {
flush_dcache_mmap_lock(mapping);
vma_interval_tree_remove(vma, root);
if (adjust_next)
vma_interval_tree_remove(next, root);
}
if (start != vma->vm_start) {
vma->vm_start = start;
start_changed = true;
}
if (end != vma->vm_end) {
vma->vm_end = end;
end_changed = true;
}
vma->vm_pgoff = pgoff;
if (adjust_next) {
next->vm_start += adjust_next << PAGE_SHIFT;
next->vm_pgoff += adjust_next;
}
if (root) {
if (adjust_next)
vma_interval_tree_insert(next, root);
vma_interval_tree_insert(vma, root);
flush_dcache_mmap_unlock(mapping);
}
if (remove_next) {
/*
* vma_merge has merged next into vma, and needs
* us to remove next before dropping the locks.
*/
__vma_unlink(mm, next, vma);
if (file)
__remove_shared_vm_struct(next, file, mapping);
} else if (insert) {
/*
* split_vma has split insert from vma, and needs
* us to insert it before dropping the locks
* (it may either follow vma or precede it).
*/
__insert_vm_struct(mm, insert);
} else {
if (start_changed)
vma_gap_update(vma);
if (end_changed) {
if (!next)
mm->highest_vm_end = end;
else if (!adjust_next)
vma_gap_update(next);
}
}
if (anon_vma) {
anon_vma_interval_tree_post_update_vma(vma);
if (adjust_next)
anon_vma_interval_tree_post_update_vma(next);
anon_vma_unlock_write(anon_vma);
}
if (mapping)
mutex_unlock(&mapping->i_mmap_mutex);
if (root) {
uprobe_mmap(vma);
if (adjust_next)
uprobe_mmap(next);
}
if (remove_next) {
if (file) {
uprobe_munmap(next, next->vm_start, next->vm_end);
fput(file);
}
if (next->anon_vma)
anon_vma_merge(vma, next);
mm->map_count--;
mpol_put(vma_policy(next));
kmem_cache_free(vm_area_cachep, next);
/*
* In mprotect's case 6 (see comments on vma_merge),
* we must remove another next too. It would clutter
* up the code too much to do both in one go.
*/
next = vma->vm_next;
if (remove_next == 2)
goto again;
else if (next)
vma_gap_update(next);
else
mm->highest_vm_end = end;
}
if (insert && file)
uprobe_mmap(insert);
validate_mm(mm);
return 0;
}
/*
* If the vma has a ->close operation then the driver probably needs to release
* per-vma resources, so we don't attempt to merge those.
*/
static inline int is_mergeable_vma(struct vm_area_struct *vma,
struct file *file, unsigned long vm_flags)
{
/*
* VM_SOFTDIRTY should not prevent from VMA merging, if we
* match the flags but dirty bit -- the caller should mark
* merged VMA as dirty. If dirty bit won't be excluded from
* comparison, we increase pressue on the memory system forcing
* the kernel to generate new VMAs when old one could be
* extended instead.
*/
if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
return 0;
if (vma->vm_file != file)
return 0;
if (vma->vm_ops && vma->vm_ops->close)
return 0;
return 1;
}
static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
struct anon_vma *anon_vma2,
struct vm_area_struct *vma)
{
/*
* The list_is_singular() test is to avoid merging VMA cloned from
* parents. This can improve scalability caused by anon_vma lock.
*/
if ((!anon_vma1 || !anon_vma2) && (!vma ||
list_is_singular(&vma->anon_vma_chain)))
return 1;
return anon_vma1 == anon_vma2;
}
/*
* Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
* in front of (at a lower virtual address and file offset than) the vma.
*
* We cannot merge two vmas if they have differently assigned (non-NULL)
* anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
*
* We don't check here for the merged mmap wrapping around the end of pagecache
* indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
* wrap, nor mmaps which cover the final page at index -1UL.
*/
static int
can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
{
if (is_mergeable_vma(vma, file, vm_flags) &&
is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
if (vma->vm_pgoff == vm_pgoff)
return 1;
}
return 0;
}
/*
* Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
* beyond (at a higher virtual address and file offset than) the vma.
*
* We cannot merge two vmas if they have differently assigned (non-NULL)
* anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
*/
static int
can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file, pgoff_t vm_pgoff)
{
if (is_mergeable_vma(vma, file, vm_flags) &&
is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
pgoff_t vm_pglen;
vm_pglen = vma_pages(vma);
if (vma->vm_pgoff + vm_pglen == vm_pgoff)
return 1;
}
return 0;
}
/*
* Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
* whether that can be merged with its predecessor or its successor.
* Or both (it neatly fills a hole).
*
* In most cases - when called for mmap, brk or mremap - [addr,end) is
* certain not to be mapped by the time vma_merge is called; but when
* called for mprotect, it is certain to be already mapped (either at
* an offset within prev, or at the start of next), and the flags of
* this area are about to be changed to vm_flags - and the no-change
* case has already been eliminated.
*
* The following mprotect cases have to be considered, where AAAA is
* the area passed down from mprotect_fixup, never extending beyond one
* vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
*
* AAAA AAAA AAAA AAAA
* PPPPPPNNNNNN PPPPPPNNNNNN PPPPPPNNNNNN PPPPNNNNXXXX
* cannot merge might become might become might become
* PPNNNNNNNNNN PPPPPPPPPPNN PPPPPPPPPPPP 6 or
* mmap, brk or case 4 below case 5 below PPPPPPPPXXXX 7 or
* mremap move: PPPPNNNNNNNN 8
* AAAA
* PPPP NNNN PPPPPPPPPPPP PPPPPPPPNNNN PPPPNNNNNNNN
* might become case 1 below case 2 below case 3 below
*
* Odd one out? Case 8, because it extends NNNN but needs flags of XXXX:
* mprotect_fixup updates vm_flags & vm_page_prot on successful return.
*/
struct vm_area_struct *vma_merge(struct mm_struct *mm,
struct vm_area_struct *prev, unsigned long addr,
unsigned long end, unsigned long vm_flags,
struct anon_vma *anon_vma, struct file *file,
pgoff_t pgoff, struct mempolicy *policy)
{
pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
struct vm_area_struct *area, *next;
int err;
/*
* We later require that vma->vm_flags == vm_flags,
* so this tests vma->vm_flags & VM_SPECIAL, too.
*/
if (vm_flags & VM_SPECIAL)
return NULL;
if (prev)
next = prev->vm_next;
else
next = mm->mmap;
area = next;
if (next && next->vm_end == end) /* cases 6, 7, 8 */
next = next->vm_next;
/*
* Can it merge with the predecessor?
*/
if (prev && prev->vm_end == addr &&
mpol_equal(vma_policy(prev), policy) &&
can_vma_merge_after(prev, vm_flags,
anon_vma, file, pgoff)) {
/*
* OK, it can. Can we now merge in the successor as well?
*/
if (next && end == next->vm_start &&
mpol_equal(policy, vma_policy(next)) &&
can_vma_merge_before(next, vm_flags,
anon_vma, file, pgoff+pglen) &&
is_mergeable_anon_vma(prev->anon_vma,
next->anon_vma, NULL)) {
/* cases 1, 6 */
err = vma_adjust(prev, prev->vm_start,
next->vm_end, prev->vm_pgoff, NULL);
} else /* cases 2, 5, 7 */
err = vma_adjust(prev, prev->vm_start,
end, prev->vm_pgoff, NULL);
if (err)
return NULL;
khugepaged_enter_vma_merge(prev);
return prev;
}
/*
* Can this new request be merged in front of next?
*/
if (next && end == next->vm_start &&
mpol_equal(policy, vma_policy(next)) &&
can_vma_merge_before(next, vm_flags,
anon_vma, file, pgoff+pglen)) {
if (prev && addr < prev->vm_end) /* case 4 */
err = vma_adjust(prev, prev->vm_start,
addr, prev->vm_pgoff, NULL);
else /* cases 3, 8 */
err = vma_adjust(area, addr, next->vm_end,
next->vm_pgoff - pglen, NULL);
if (err)
return NULL;
khugepaged_enter_vma_merge(area);
return area;
}
return NULL;
}
/*
* Rough compatbility check to quickly see if it's even worth looking
* at sharing an anon_vma.
*
* They need to have the same vm_file, and the flags can only differ
* in things that mprotect may change.
*
* NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
* we can merge the two vma's. For example, we refuse to merge a vma if
* there is a vm_ops->close() function, because that indicates that the
* driver is doing some kind of reference counting. But that doesn't
* really matter for the anon_vma sharing case.
*/
static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
{
return a->vm_end == b->vm_start &&
mpol_equal(vma_policy(a), vma_policy(b)) &&
a->vm_file == b->vm_file &&
!((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
}
/*
* Do some basic sanity checking to see if we can re-use the anon_vma
* from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
* the same as 'old', the other will be the new one that is trying
* to share the anon_vma.
*
* NOTE! This runs with mm_sem held for reading, so it is possible that
* the anon_vma of 'old' is concurrently in the process of being set up
* by another page fault trying to merge _that_. But that's ok: if it
* is being set up, that automatically means that it will be a singleton
* acceptable for merging, so we can do all of this optimistically. But
* we do that ACCESS_ONCE() to make sure that we never re-load the pointer.
*
* IOW: that the "list_is_singular()" test on the anon_vma_chain only
* matters for the 'stable anon_vma' case (ie the thing we want to avoid
* is to return an anon_vma that is "complex" due to having gone through
* a fork).
*
* We also make sure that the two vma's are compatible (adjacent,
* and with the same memory policies). That's all stable, even with just
* a read lock on the mm_sem.
*/
static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
{
if (anon_vma_compatible(a, b)) {
struct anon_vma *anon_vma = ACCESS_ONCE(old->anon_vma);
if (anon_vma && list_is_singular(&old->anon_vma_chain))
return anon_vma;
}
return NULL;
}
/*
* find_mergeable_anon_vma is used by anon_vma_prepare, to check
* neighbouring vmas for a suitable anon_vma, before it goes off
* to allocate a new anon_vma. It checks because a repetitive
* sequence of mprotects and faults may otherwise lead to distinct
* anon_vmas being allocated, preventing vma merge in subsequent
* mprotect.
*/
struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
{
struct anon_vma *anon_vma;
struct vm_area_struct *near;
near = vma->vm_next;
if (!near)
goto try_prev;
anon_vma = reusable_anon_vma(near, vma, near);
if (anon_vma)
return anon_vma;
try_prev:
near = vma->vm_prev;
if (!near)
goto none;
anon_vma = reusable_anon_vma(near, near, vma);
if (anon_vma)
return anon_vma;
none:
/*
* There's no absolute need to look only at touching neighbours:
* we could search further afield for "compatible" anon_vmas.
* But it would probably just be a waste of time searching,
* or lead to too many vmas hanging off the same anon_vma.
* We're trying to allow mprotect remerging later on,
* not trying to minimize memory used for anon_vmas.
*/
return NULL;
}
#ifdef CONFIG_PROC_FS
void vm_stat_account(struct mm_struct *mm, unsigned long flags,
struct file *file, long pages)
{
const unsigned long stack_flags
= VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
mm->total_vm += pages;
if (file) {
mm->shared_vm += pages;
if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
mm->exec_vm += pages;
} else if (flags & stack_flags)
mm->stack_vm += pages;
}
#endif /* CONFIG_PROC_FS */
/*
* If a hint addr is less than mmap_min_addr change hint to be as
* low as possible but still greater than mmap_min_addr
*/
static inline unsigned long round_hint_to_min(unsigned long hint)
{
hint &= PAGE_MASK;
if (((void *)hint != NULL) &&
(hint < mmap_min_addr))
return PAGE_ALIGN(mmap_min_addr);
return hint;
}
static inline int mlock_future_check(struct mm_struct *mm,
unsigned long flags,
unsigned long len)
{
unsigned long locked, lock_limit;
/* mlock MCL_FUTURE? */
if (flags & VM_LOCKED) {
locked = len >> PAGE_SHIFT;
locked += mm->locked_vm;
lock_limit = rlimit(RLIMIT_MEMLOCK);
lock_limit >>= PAGE_SHIFT;
if (locked > lock_limit && !capable(CAP_IPC_LOCK))
return -EAGAIN;
}
return 0;
}
/*
* The caller must hold down_write(&current->mm->mmap_sem).
*/
unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
unsigned long len, unsigned long prot,
unsigned long flags, unsigned long pgoff,
unsigned long *populate)
{
struct mm_struct * mm = current->mm;
vm_flags_t vm_flags;
*populate = 0;
/*
* Does the application expect PROT_READ to imply PROT_EXEC?
*
* (the exception is when the underlying filesystem is noexec
* mounted, in which case we dont add PROT_EXEC.)
*/
if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
if (!(file && (file->f_path.mnt->mnt_flags & MNT_NOEXEC)))
prot |= PROT_EXEC;
if (!len)
return -EINVAL;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
/* Careful about overflows.. */
len = PAGE_ALIGN(len);
if (!len)
return -ENOMEM;
/* offset overflow? */
if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
return -EOVERFLOW;
/* Too many mappings? */
if (mm->map_count > sysctl_max_map_count)
return -ENOMEM;
/* Obtain the address to map to. we verify (or select) it and ensure
* that it represents a valid section of the address space.
*/
addr = get_unmapped_area(file, addr, len, pgoff, flags);
if (addr & ~PAGE_MASK)
return addr;
/* Do simple checking here so the lower-level routines won't have
* to. we assume access permissions have been handled by the open
* of the memory object, so we don't do any here.
*/
vm_flags = calc_vm_prot_bits(prot) | calc_vm_flag_bits(flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
if (flags & MAP_LOCKED)
if (!can_do_mlock())
return -EPERM;
if (mlock_future_check(mm, vm_flags, len))
return -EAGAIN;
if (file) {
struct inode *inode = file_inode(file);
switch (flags & MAP_TYPE) {
case MAP_SHARED:
if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
return -EACCES;
/*
* Make sure we don't allow writing to an append-only
* file..
*/
if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
return -EACCES;
/*
* Make sure there are no mandatory locks on the file.
*/
if (locks_verify_locked(file))
return -EAGAIN;
vm_flags |= VM_SHARED | VM_MAYSHARE;
if (!(file->f_mode & FMODE_WRITE))
vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
/* fall through */
case MAP_PRIVATE:
if (!(file->f_mode & FMODE_READ))
return -EACCES;
if (file->f_path.mnt->mnt_flags & MNT_NOEXEC) {
if (vm_flags & VM_EXEC)
return -EPERM;
vm_flags &= ~VM_MAYEXEC;
}
if (!file->f_op->mmap)
return -ENODEV;
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
break;
default:
return -EINVAL;
}
} else {
switch (flags & MAP_TYPE) {
case MAP_SHARED:
if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
return -EINVAL;
/*
* Ignore pgoff.
*/
pgoff = 0;
vm_flags |= VM_SHARED | VM_MAYSHARE;
break;
case MAP_PRIVATE:
/*
* Set pgoff according to addr for anon_vma.
*/
pgoff = addr >> PAGE_SHIFT;
break;
default:
return -EINVAL;
}
}
/*
* Set 'VM_NORESERVE' if we should not account for the
* memory use of this mapping.
*/
if (flags & MAP_NORESERVE) {
/* We honor MAP_NORESERVE if allowed to overcommit */
if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
vm_flags |= VM_NORESERVE;
/* hugetlb applies strict overcommit unless MAP_NORESERVE */
if (file && is_file_hugepages(file))
vm_flags |= VM_NORESERVE;
}
addr = mmap_region(file, addr, len, vm_flags, pgoff);
if (!IS_ERR_VALUE(addr) &&
((vm_flags & VM_LOCKED) ||
(flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
*populate = len;
return addr;
}
SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags,
unsigned long, fd, unsigned long, pgoff)
{
struct file *file = NULL;
unsigned long retval = -EBADF;
if (!(flags & MAP_ANONYMOUS)) {
audit_mmap_fd(fd, flags);
file = fget(fd);
if (!file)
goto out;
if (is_file_hugepages(file))
len = ALIGN(len, huge_page_size(hstate_file(file)));
retval = -EINVAL;
if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
goto out_fput;
} else if (flags & MAP_HUGETLB) {
struct user_struct *user = NULL;
struct hstate *hs;
hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & SHM_HUGE_MASK);
if (!hs)
return -EINVAL;
len = ALIGN(len, huge_page_size(hs));
/*
* VM_NORESERVE is used because the reservations will be
* taken when vm_ops->mmap() is called
* A dummy user value is used because we are not locking
* memory so no accounting is necessary
*/
file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
VM_NORESERVE,
&user, HUGETLB_ANONHUGE_INODE,
(flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
if (IS_ERR(file))
return PTR_ERR(file);
}
flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
out_fput:
if (file)
fput(file);
out:
return retval;
}
#ifdef __ARCH_WANT_SYS_OLD_MMAP
struct mmap_arg_struct {
unsigned long addr;
unsigned long len;
unsigned long prot;
unsigned long flags;
unsigned long fd;
unsigned long offset;
};
SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
{
struct mmap_arg_struct a;
if (copy_from_user(&a, arg, sizeof(a)))
return -EFAULT;
if (a.offset & ~PAGE_MASK)
return -EINVAL;
return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
a.offset >> PAGE_SHIFT);
}
#endif /* __ARCH_WANT_SYS_OLD_MMAP */
/*
* Some shared mappigns will want the pages marked read-only
* to track write events. If so, we'll downgrade vm_page_prot
* to the private version (using protection_map[] without the
* VM_SHARED bit).
*/
int vma_wants_writenotify(struct vm_area_struct *vma)
{
vm_flags_t vm_flags = vma->vm_flags;
/* If it was private or non-writable, the write bit is already clear */
if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
return 0;
/* The backer wishes to know when pages are first written to? */
if (vma->vm_ops && vma->vm_ops->page_mkwrite)
return 1;
/* The open routine did something to the protections already? */
if (pgprot_val(vma->vm_page_prot) !=
pgprot_val(vm_get_page_prot(vm_flags)))
return 0;
/* Specialty mapping? */
if (vm_flags & VM_PFNMAP)
return 0;
/* Can the mapping track the dirty pages? */
return vma->vm_file && vma->vm_file->f_mapping &&
mapping_cap_account_dirty(vma->vm_file->f_mapping);
}
/*
* We account for memory if it's a private writeable mapping,
* not hugepages and VM_NORESERVE wasn't set.
*/
static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
{
/*
* hugetlb has its own accounting separate from the core VM
* VM_HUGETLB may not be set yet so we cannot check for that flag.
*/
if (file && is_file_hugepages(file))
return 0;
return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
}
unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev;
int error;
struct rb_node **rb_link, *rb_parent;
unsigned long charged = 0;
/* Check against address space limit. */
if (!may_expand_vm(mm, len >> PAGE_SHIFT)) {
unsigned long nr_pages;
/*
* MAP_FIXED may remove pages of mappings that intersects with
* requested mapping. Account for the pages it would unmap.
*/
if (!(vm_flags & MAP_FIXED))
return -ENOMEM;
nr_pages = count_vma_pages_range(mm, addr, addr + len);
if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
return -ENOMEM;
}
/* Clear old maps */
error = -ENOMEM;
munmap_back:
if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
if (do_munmap(mm, addr, len))
return -ENOMEM;
goto munmap_back;
}
/*
* Private writable mapping: check memory availability
*/
if (accountable_mapping(file, vm_flags)) {
charged = len >> PAGE_SHIFT;
if (security_vm_enough_memory_mm(mm, charged))
return -ENOMEM;
vm_flags |= VM_ACCOUNT;
}
/*
* Can we just expand an old mapping?
*/
vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
if (vma)
goto out;
/*
* Determine the object being mapped and call the appropriate
* specific mapper. the address has already been validated, but
* not unmapped, but the maps are removed from the list.
*/
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (!vma) {
error = -ENOMEM;
goto unacct_error;
}
vma->vm_mm = mm;
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_flags = vm_flags;
vma->vm_page_prot = vm_get_page_prot(vm_flags);
vma->vm_pgoff = pgoff;
INIT_LIST_HEAD(&vma->anon_vma_chain);
if (file) {
if (vm_flags & VM_DENYWRITE) {
error = deny_write_access(file);
if (error)
goto free_vma;
}
vma->vm_file = get_file(file);
error = file->f_op->mmap(file, vma);
if (error)
goto unmap_and_free_vma;
/* Can addr have changed??
*
* Answer: Yes, several device drivers can do it in their
* f_op->mmap method. -DaveM
* Bug: If addr is changed, prev, rb_link, rb_parent should
* be updated for vma_link()
*/
WARN_ON_ONCE(addr != vma->vm_start);
addr = vma->vm_start;
vm_flags = vma->vm_flags;
} else if (vm_flags & VM_SHARED) {
error = shmem_zero_setup(vma);
if (error)
goto free_vma;
}
if (vma_wants_writenotify(vma)) {
pgprot_t pprot = vma->vm_page_prot;
/* Can vma->vm_page_prot have changed??
*
* Answer: Yes, drivers may have changed it in their
* f_op->mmap method.
*
* Ensures that vmas marked as uncached stay that way.
*/
vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
if (pgprot_val(pprot) == pgprot_val(pgprot_noncached(pprot)))
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
}
vma_link(mm, vma, prev, rb_link, rb_parent);
/* Once vma denies write, undo our temporary denial count */
if (vm_flags & VM_DENYWRITE)
allow_write_access(file);
file = vma->vm_file;
out:
perf_event_mmap(vma);
vm_stat_account(mm, vm_flags, file, len >> PAGE_SHIFT);
if (vm_flags & VM_LOCKED) {
if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
vma == get_gate_vma(current->mm)))
mm->locked_vm += (len >> PAGE_SHIFT);
else
vma->vm_flags &= ~VM_LOCKED;
}
if (file)
uprobe_mmap(vma);
/*
* New (or expanded) vma always get soft dirty status.
* Otherwise user-space soft-dirty page tracker won't
* be able to distinguish situation when vma area unmapped,
* then new mapped in-place (which must be aimed as
* a completely new data area).
*/
vma->vm_flags |= VM_SOFTDIRTY;
return addr;
unmap_and_free_vma:
if (vm_flags & VM_DENYWRITE)
allow_write_access(file);
vma->vm_file = NULL;
fput(file);
/* Undo any partial mapping done by a device driver. */
unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
charged = 0;
free_vma:
kmem_cache_free(vm_area_cachep, vma);
unacct_error:
if (charged)
vm_unacct_memory(charged);
return error;
}
unsigned long unmapped_area(struct vm_unmapped_area_info *info)
{
/*
* We implement the search by looking for an rbtree node that
* immediately follows a suitable gap. That is,
* - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
* - gap_end = vma->vm_start >= info->low_limit + length;
* - gap_end - gap_start >= length
*/
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long length, low_limit, high_limit, gap_start, gap_end;
/* Adjust search length to account for worst case alignment overhead */
length = info->length + info->align_mask;
if (length < info->length)
return -ENOMEM;
/* Adjust search limits by the desired length */
if (info->high_limit < length)
return -ENOMEM;
high_limit = info->high_limit - length;
if (info->low_limit > high_limit)
return -ENOMEM;
low_limit = info->low_limit + length;
/* Check if rbtree root looks promising */
if (RB_EMPTY_ROOT(&mm->mm_rb))
goto check_highest;
vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
if (vma->rb_subtree_gap < length)
goto check_highest;
while (true) {
/* Visit left subtree if it looks promising */
gap_end = vma->vm_start;
if (gap_end >= low_limit && vma->vm_rb.rb_left) {
struct vm_area_struct *left =
rb_entry(vma->vm_rb.rb_left,
struct vm_area_struct, vm_rb);
if (left->rb_subtree_gap >= length) {
vma = left;
continue;
}
}
gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
check_current:
/* Check if current node has a suitable gap */
if (gap_start > high_limit)
return -ENOMEM;
if (gap_end >= low_limit && gap_end - gap_start >= length)
goto found;
/* Visit right subtree if it looks promising */
if (vma->vm_rb.rb_right) {
struct vm_area_struct *right =
rb_entry(vma->vm_rb.rb_right,
struct vm_area_struct, vm_rb);
if (right->rb_subtree_gap >= length) {
vma = right;
continue;
}
}
/* Go back up the rbtree to find next candidate node */
while (true) {
struct rb_node *prev = &vma->vm_rb;
if (!rb_parent(prev))
goto check_highest;
vma = rb_entry(rb_parent(prev),
struct vm_area_struct, vm_rb);
if (prev == vma->vm_rb.rb_left) {
gap_start = vma->vm_prev->vm_end;
gap_end = vma->vm_start;
goto check_current;
}
}
}
check_highest:
/* Check highest gap, which does not precede any rbtree node */
gap_start = mm->highest_vm_end;
gap_end = ULONG_MAX; /* Only for VM_BUG_ON below */
if (gap_start > high_limit)
return -ENOMEM;
found:
/* We found a suitable gap. Clip it with the original low_limit. */
if (gap_start < info->low_limit)
gap_start = info->low_limit;
/* Adjust gap address to the desired alignment */
gap_start += (info->align_offset - gap_start) & info->align_mask;
VM_BUG_ON(gap_start + info->length > info->high_limit);
VM_BUG_ON(gap_start + info->length > gap_end);
return gap_start;
}
unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long length, low_limit, high_limit, gap_start, gap_end;
/* Adjust search length to account for worst case alignment overhead */
length = info->length + info->align_mask;
if (length < info->length)
return -ENOMEM;
/*
* Adjust search limits by the desired length.
* See implementation comment at top of unmapped_area().
*/
gap_end = info->high_limit;
if (gap_end < length)
return -ENOMEM;
high_limit = gap_end - length;
if (info->low_limit > high_limit)
return -ENOMEM;
low_limit = info->low_limit + length;
/* Check highest gap, which does not precede any rbtree node */
gap_start = mm->highest_vm_end;
if (gap_start <= high_limit)
goto found_highest;
/* Check if rbtree root looks promising */
if (RB_EMPTY_ROOT(&mm->mm_rb))
return -ENOMEM;
vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
if (vma->rb_subtree_gap < length)
return -ENOMEM;
while (true) {
/* Visit right subtree if it looks promising */
gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
if (gap_start <= high_limit && vma->vm_rb.rb_right) {
struct vm_area_struct *right =
rb_entry(vma->vm_rb.rb_right,
struct vm_area_struct, vm_rb);
if (right->rb_subtree_gap >= length) {
vma = right;
continue;
}
}
check_current:
/* Check if current node has a suitable gap */
gap_end = vma->vm_start;
if (gap_end < low_limit)
return -ENOMEM;
if (gap_start <= high_limit && gap_end - gap_start >= length)
goto found;
/* Visit left subtree if it looks promising */
if (vma->vm_rb.rb_left) {
struct vm_area_struct *left =
rb_entry(vma->vm_rb.rb_left,
struct vm_area_struct, vm_rb);
if (left->rb_subtree_gap >= length) {
vma = left;
continue;
}
}
/* Go back up the rbtree to find next candidate node */
while (true) {
struct rb_node *prev = &vma->vm_rb;
if (!rb_parent(prev))
return -ENOMEM;
vma = rb_entry(rb_parent(prev),
struct vm_area_struct, vm_rb);
if (prev == vma->vm_rb.rb_right) {
gap_start = vma->vm_prev ?
vma->vm_prev->vm_end : 0;
goto check_current;
}
}
}
found:
/* We found a suitable gap. Clip it with the original high_limit. */
if (gap_end > info->high_limit)
gap_end = info->high_limit;
found_highest:
/* Compute highest gap address at the desired alignment */
gap_end -= info->length;
gap_end -= (gap_end - info->align_offset) & info->align_mask;
VM_BUG_ON(gap_end < info->low_limit);
VM_BUG_ON(gap_end < gap_start);
return gap_end;
}
/* Get an address range which is currently unmapped.
* For shmat() with addr=0.
*
* Ugly calling convention alert:
* Return value with the low bits set means error value,
* ie
* if (ret & ~PAGE_MASK)
* error = ret;
*
* This function "knows" that -ENOMEM has the bits set.
*/
#ifndef HAVE_ARCH_UNMAPPED_AREA
unsigned long
arch_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
struct vm_unmapped_area_info info;
if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
return addr;
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vma->vm_start))
return addr;
}
info.flags = 0;
info.length = len;
info.low_limit = mm->mmap_base;
info.high_limit = TASK_SIZE;
info.align_mask = 0;
return vm_unmapped_area(&info);
}
#endif
/*
* This mmap-allocator allocates new areas top-down from below the
* stack's low limit (the base):
*/
#ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
unsigned long
arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
const unsigned long len, const unsigned long pgoff,
const unsigned long flags)
{
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
struct vm_unmapped_area_info info;
/* requested length too big for entire address space */
if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
if (flags & MAP_FIXED)
return addr;
/* requesting a specific address */
if (addr) {
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
(!vma || addr + len <= vma->vm_start))
return addr;
}
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = max(PAGE_SIZE, mmap_min_addr);
info.high_limit = mm->mmap_base;
info.align_mask = 0;
addr = vm_unmapped_area(&info);
/*
* A failed mmap() very likely causes application failure,
* so fall back to the bottom-up function here. This scenario
* can happen with large stack limits and large mmap()
* allocations.
*/
if (addr & ~PAGE_MASK) {
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
info.low_limit = TASK_UNMAPPED_BASE;
info.high_limit = TASK_SIZE;
addr = vm_unmapped_area(&info);
}
return addr;
}
#endif
unsigned long
get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
unsigned long error = arch_mmap_check(addr, len, flags);
if (error)
return error;
/* Careful about overflows.. */
if (len > TASK_SIZE)
return -ENOMEM;
get_area = current->mm->get_unmapped_area;
if (file && file->f_op->get_unmapped_area)
get_area = file->f_op->get_unmapped_area;
addr = get_area(file, addr, len, pgoff, flags);
if (IS_ERR_VALUE(addr))
return addr;
if (addr > TASK_SIZE - len)
return -ENOMEM;
if (addr & ~PAGE_MASK)
return -EINVAL;
addr = arch_rebalance_pgtables(addr, len);
error = security_mmap_addr(addr);
return error ? error : addr;
}
EXPORT_SYMBOL(get_unmapped_area);
/* Look up the first VMA which satisfies addr < vm_end, NULL if none. */
struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
{
struct rb_node *rb_node;
struct vm_area_struct *vma;
/* Check the cache first. */
vma = vmacache_find(mm, addr);
if (likely(vma))
return vma;
rb_node = mm->mm_rb.rb_node;
vma = NULL;
while (rb_node) {
struct vm_area_struct *tmp;
tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
if (tmp->vm_end > addr) {
vma = tmp;
if (tmp->vm_start <= addr)
break;
rb_node = rb_node->rb_left;
} else
rb_node = rb_node->rb_right;
}
if (vma)
vmacache_update(addr, vma);
return vma;
}
EXPORT_SYMBOL(find_vma);
/*
* Same as find_vma, but also return a pointer to the previous VMA in *pprev.
*/
struct vm_area_struct *
find_vma_prev(struct mm_struct *mm, unsigned long addr,
struct vm_area_struct **pprev)
{
struct vm_area_struct *vma;
vma = find_vma(mm, addr);
if (vma) {
*pprev = vma->vm_prev;
} else {
struct rb_node *rb_node = mm->mm_rb.rb_node;
*pprev = NULL;
while (rb_node) {
*pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
rb_node = rb_node->rb_right;
}
}
return vma;
}
/*
* Verify that the stack growth is acceptable and
* update accounting. This is shared with both the
* grow-up and grow-down cases.
*/
static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
{
struct mm_struct *mm = vma->vm_mm;
struct rlimit *rlim = current->signal->rlim;
unsigned long new_start;
/* address space limit tests */
if (!may_expand_vm(mm, grow))
return -ENOMEM;
/* Stack limit test */
if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
return -ENOMEM;
/* mlock limit tests */
if (vma->vm_flags & VM_LOCKED) {
unsigned long locked;
unsigned long limit;
locked = mm->locked_vm + grow;
limit = ACCESS_ONCE(rlim[RLIMIT_MEMLOCK].rlim_cur);
limit >>= PAGE_SHIFT;
if (locked > limit && !capable(CAP_IPC_LOCK))
return -ENOMEM;
}
/* Check to ensure the stack will not grow into a hugetlb-only region */
new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
vma->vm_end - size;
if (is_hugepage_only_range(vma->vm_mm, new_start, size))
return -EFAULT;
/*
* Overcommit.. This must be the final test, as it will
* update security statistics.
*/
if (security_vm_enough_memory_mm(mm, grow))
return -ENOMEM;
/* Ok, everything looks good - let it rip */
if (vma->vm_flags & VM_LOCKED)
mm->locked_vm += grow;
vm_stat_account(mm, vma->vm_flags, vma->vm_file, grow);
return 0;
}
#if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
/*
* PA-RISC uses this for its stack; IA64 for its Register Backing Store.
* vma is the last one with address > vma->vm_end. Have to extend vma.
*/
int expand_upwards(struct vm_area_struct *vma, unsigned long address)
{
int error;
if (!(vma->vm_flags & VM_GROWSUP))
return -EFAULT;
/*
* We must make sure the anon_vma is allocated
* so that the anon_vma locking is not a noop.
*/
if (unlikely(anon_vma_prepare(vma)))
return -ENOMEM;
vma_lock_anon_vma(vma);
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
* Also guard against wrapping around to address 0.
*/
if (address < PAGE_ALIGN(address+4))
address = PAGE_ALIGN(address+4);
else {
vma_unlock_anon_vma(vma);
return -ENOMEM;
}
error = 0;
/* Somebody else might have raced and expanded it already */
if (address > vma->vm_end) {
unsigned long size, grow;
size = address - vma->vm_start;
grow = (address - vma->vm_end) >> PAGE_SHIFT;
error = -ENOMEM;
if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
/*
* vma_gap_update() doesn't support concurrent
* updates, but we only hold a shared mmap_sem
* lock here, so we need to protect against
* concurrent vma expansions.
* vma_lock_anon_vma() doesn't help here, as
* we don't guarantee that all growable vmas
* in a mm share the same root anon vma.
* So, we reuse mm->page_table_lock to guard
* against concurrent vma expansions.
*/
spin_lock(&vma->vm_mm->page_table_lock);
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_end = address;
anon_vma_interval_tree_post_update_vma(vma);
if (vma->vm_next)
vma_gap_update(vma->vm_next);
else
vma->vm_mm->highest_vm_end = address;
spin_unlock(&vma->vm_mm->page_table_lock);
perf_event_mmap(vma);
}
}
}
vma_unlock_anon_vma(vma);
khugepaged_enter_vma_merge(vma);
validate_mm(vma->vm_mm);
return error;
}
#endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
/*
* vma is the first one with address < vma->vm_start. Have to extend vma.
*/
int expand_downwards(struct vm_area_struct *vma,
unsigned long address)
{
int error;
/*
* We must make sure the anon_vma is allocated
* so that the anon_vma locking is not a noop.
*/
if (unlikely(anon_vma_prepare(vma)))
return -ENOMEM;
address &= PAGE_MASK;
error = security_mmap_addr(address);
if (error)
return error;
vma_lock_anon_vma(vma);
/*
* vma->vm_start/vm_end cannot change under us because the caller
* is required to hold the mmap_sem in read mode. We need the
* anon_vma lock to serialize against concurrent expand_stacks.
*/
/* Somebody else might have raced and expanded it already */
if (address < vma->vm_start) {
unsigned long size, grow;
size = vma->vm_end - address;
grow = (vma->vm_start - address) >> PAGE_SHIFT;
error = -ENOMEM;
if (grow <= vma->vm_pgoff) {
error = acct_stack_growth(vma, size, grow);
if (!error) {
/*
* vma_gap_update() doesn't support concurrent
* updates, but we only hold a shared mmap_sem
* lock here, so we need to protect against
* concurrent vma expansions.
* vma_lock_anon_vma() doesn't help here, as
* we don't guarantee that all growable vmas
* in a mm share the same root anon vma.
* So, we reuse mm->page_table_lock to guard
* against concurrent vma expansions.
*/
spin_lock(&vma->vm_mm->page_table_lock);
anon_vma_interval_tree_pre_update_vma(vma);
vma->vm_start = address;
vma->vm_pgoff -= grow;
anon_vma_interval_tree_post_update_vma(vma);
vma_gap_update(vma);
spin_unlock(&vma->vm_mm->page_table_lock);
perf_event_mmap(vma);
}
}
}
vma_unlock_anon_vma(vma);
khugepaged_enter_vma_merge(vma);
validate_mm(vma->vm_mm);
return error;
}
/*
* Note how expand_stack() refuses to expand the stack all the way to
* abut the next virtual mapping, *unless* that mapping itself is also
* a stack mapping. We want to leave room for a guard page, after all
* (the guard page itself is not added here, that is done by the
* actual page faulting logic)
*
* This matches the behavior of the guard page logic (see mm/memory.c:
* check_stack_guard_page()), which only allows the guard page to be
* removed under these circumstances.
*/
#ifdef CONFIG_STACK_GROWSUP
int expand_stack(struct vm_area_struct *vma, unsigned long address)
{
struct vm_area_struct *next;
address &= PAGE_MASK;
next = vma->vm_next;
if (next && next->vm_start == address + PAGE_SIZE) {
if (!(next->vm_flags & VM_GROWSUP))
return -ENOMEM;
}
return expand_upwards(vma, address);
}
struct vm_area_struct *
find_extend_vma(struct mm_struct *mm, unsigned long addr)
{
struct vm_area_struct *vma, *prev;
addr &= PAGE_MASK;
vma = find_vma_prev(mm, addr, &prev);
if (vma && (vma->vm_start <= addr))
return vma;
if (!prev || expand_stack(prev, addr))
return NULL;
if (prev->vm_flags & VM_LOCKED)
__mlock_vma_pages_range(prev, addr, prev->vm_end, NULL);
return prev;
}
#else
int expand_stack(struct vm_area_struct *vma, unsigned long address)
{
struct vm_area_struct *prev;
address &= PAGE_MASK;
prev = vma->vm_prev;
if (prev && prev->vm_end == address) {
if (!(prev->vm_flags & VM_GROWSDOWN))
return -ENOMEM;
}
return expand_downwards(vma, address);
}
struct vm_area_struct *
find_extend_vma(struct mm_struct * mm, unsigned long addr)
{
struct vm_area_struct * vma;
unsigned long start;
addr &= PAGE_MASK;
vma = find_vma(mm,addr);
if (!vma)
return NULL;
if (vma->vm_start <= addr)
return vma;
if (!(vma->vm_flags & VM_GROWSDOWN))
return NULL;
start = vma->vm_start;
if (expand_stack(vma, addr))
return NULL;
if (vma->vm_flags & VM_LOCKED)
__mlock_vma_pages_range(vma, addr, start, NULL);
return vma;
}
#endif
/*
* Ok - we have the memory areas we should free on the vma list,
* so release them, and do the vma updates.
*
* Called with the mm semaphore held.
*/
static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
{
unsigned long nr_accounted = 0;
/* Update high watermark before we lower total_vm */
update_hiwater_vm(mm);
do {
long nrpages = vma_pages(vma);
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += nrpages;
vm_stat_account(mm, vma->vm_flags, vma->vm_file, -nrpages);
vma = remove_vma(vma);
} while (vma);
vm_unacct_memory(nr_accounted);
validate_mm(mm);
}
/*
* Get rid of page table information in the indicated region.
*
* Called with the mm semaphore held.
*/
static void unmap_region(struct mm_struct *mm,
struct vm_area_struct *vma, struct vm_area_struct *prev,
unsigned long start, unsigned long end)
{
struct vm_area_struct *next = prev? prev->vm_next: mm->mmap;
struct mmu_gather tlb;
lru_add_drain();
tlb_gather_mmu(&tlb, mm, start, end);
update_hiwater_rss(mm);
unmap_vmas(&tlb, vma, start, end);
free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
next ? next->vm_start : USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb, start, end);
}
/*
* Create a list of vma's touched by the unmap, removing them from the mm's
* vma list as we go..
*/
static void
detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, unsigned long end)
{
struct vm_area_struct **insertion_point;
struct vm_area_struct *tail_vma = NULL;
insertion_point = (prev ? &prev->vm_next : &mm->mmap);
vma->vm_prev = NULL;
do {
vma_rb_erase(vma, &mm->mm_rb);
mm->map_count--;
tail_vma = vma;
vma = vma->vm_next;
} while (vma && vma->vm_start < end);
*insertion_point = vma;
if (vma) {
vma->vm_prev = prev;
vma_gap_update(vma);
} else
mm->highest_vm_end = prev ? prev->vm_end : 0;
tail_vma->vm_next = NULL;
/* Kill the cache */
vmacache_invalidate(mm);
}
/*
* __split_vma() bypasses sysctl_max_map_count checking. We use this on the
* munmap path where it doesn't make sense to fail.
*/
static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
unsigned long addr, int new_below)
{
struct vm_area_struct *new;
int err = -ENOMEM;
if (is_vm_hugetlb_page(vma) && (addr &
~(huge_page_mask(hstate_vma(vma)))))
return -EINVAL;
new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (!new)
goto out_err;
/* most fields are the same, copy all, and then fixup */
*new = *vma;
INIT_LIST_HEAD(&new->anon_vma_chain);
if (new_below)
new->vm_end = addr;
else {
new->vm_start = addr;
new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
}
err = vma_dup_policy(vma, new);
if (err)
goto out_free_vma;
if (anon_vma_clone(new, vma))
goto out_free_mpol;
if (new->vm_file)
get_file(new->vm_file);
if (new->vm_ops && new->vm_ops->open)
new->vm_ops->open(new);
if (new_below)
err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
((addr - new->vm_start) >> PAGE_SHIFT), new);
else
err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
/* Success. */
if (!err)
return 0;
/* Clean everything up if vma_adjust failed. */
if (new->vm_ops && new->vm_ops->close)
new->vm_ops->close(new);
if (new->vm_file)
fput(new->vm_file);
unlink_anon_vmas(new);
out_free_mpol:
mpol_put(vma_policy(new));
out_free_vma:
kmem_cache_free(vm_area_cachep, new);
out_err:
return err;
}
/*
* Split a vma into two pieces at address 'addr', a new vma is allocated
* either for the first part or the tail.
*/
int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, int new_below)
{
if (mm->map_count >= sysctl_max_map_count)
return -ENOMEM;
return __split_vma(mm, vma, addr, new_below);
}
/* Munmap is split into 2 main parts -- this part which finds
* what needs doing, and the areas themselves, which do the
* work. This now handles partial unmappings.
* Jeremy Fitzhardinge <jeremy@goop.org>
*/
int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
{
unsigned long end;
struct vm_area_struct *vma, *prev, *last;
if ((start & ~PAGE_MASK) || start > TASK_SIZE || len > TASK_SIZE-start)
return -EINVAL;
if ((len = PAGE_ALIGN(len)) == 0)
return -EINVAL;
/* Find the first overlapping VMA */
vma = find_vma(mm, start);
if (!vma)
return 0;
prev = vma->vm_prev;
/* we have start < vma->vm_end */
/* if it doesn't overlap, we have nothing.. */
end = start + len;
if (vma->vm_start >= end)
return 0;
/*
* If we need to split any vma, do it now to save pain later.
*
* Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
* unmapped vm_area_struct will remain in use: so lower split_vma
* places tmp vma above, and higher split_vma places tmp vma below.
*/
if (start > vma->vm_start) {
int error;
/*
* Make sure that map_count on return from munmap() will
* not exceed its limit; but let map_count go just above
* its limit temporarily, to help free resources as expected.
*/
if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
return -ENOMEM;
error = __split_vma(mm, vma, start, 0);
if (error)
return error;
prev = vma;
}
/* Does it split the last one? */
last = find_vma(mm, end);
if (last && end > last->vm_start) {
int error = __split_vma(mm, last, end, 1);
if (error)
return error;
}
vma = prev? prev->vm_next: mm->mmap;
/*
* unlock any mlock()ed ranges before detaching vmas
*/
if (mm->locked_vm) {
struct vm_area_struct *tmp = vma;
while (tmp && tmp->vm_start < end) {
if (tmp->vm_flags & VM_LOCKED) {
mm->locked_vm -= vma_pages(tmp);
munlock_vma_pages_all(tmp);
}
tmp = tmp->vm_next;
}
}
/*
* Remove the vma's, and unmap the actual pages
*/
detach_vmas_to_be_unmapped(mm, vma, prev, end);
unmap_region(mm, vma, prev, start, end);
/* Fix up all other VM information */
remove_vma_list(mm, vma);
return 0;
}
int vm_munmap(unsigned long start, size_t len)
{
int ret;
struct mm_struct *mm = current->mm;
down_write(&mm->mmap_sem);
ret = do_munmap(mm, start, len);
up_write(&mm->mmap_sem);
return ret;
}
EXPORT_SYMBOL(vm_munmap);
SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
{
profile_munmap(addr);
return vm_munmap(addr, len);
}
static inline void verify_mm_writelocked(struct mm_struct *mm)
{
#ifdef CONFIG_DEBUG_VM
if (unlikely(down_read_trylock(&mm->mmap_sem))) {
WARN_ON(1);
up_read(&mm->mmap_sem);
}
#endif
}
/*
* this is really a simplified "do_mmap". it only handles
* anonymous maps. eventually we may be able to do some
* brk-specific accounting here.
*/
static unsigned long do_brk(unsigned long addr, unsigned long len)
{
struct mm_struct * mm = current->mm;
struct vm_area_struct * vma, * prev;
unsigned long flags;
struct rb_node ** rb_link, * rb_parent;
pgoff_t pgoff = addr >> PAGE_SHIFT;
int error;
len = PAGE_ALIGN(len);
if (!len)
return addr;
flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
if (error & ~PAGE_MASK)
return error;
error = mlock_future_check(mm, mm->def_flags, len);
if (error)
return error;
/*
* mm->mmap_sem is required to protect against another thread
* changing the mappings in case we sleep.
*/
verify_mm_writelocked(mm);
/*
* Clear old maps. this also does some error checking for us
*/
munmap_back:
if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent)) {
if (do_munmap(mm, addr, len))
return -ENOMEM;
goto munmap_back;
}
/* Check against address space limits *after* clearing old maps... */
if (!may_expand_vm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
if (mm->map_count > sysctl_max_map_count)
return -ENOMEM;
if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
/* Can we just expand an old private anonymous mapping? */
vma = vma_merge(mm, prev, addr, addr + len, flags,
NULL, NULL, pgoff, NULL);
if (vma)
goto out;
/*
* create a vma struct for an anonymous mapping
*/
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (!vma) {
vm_unacct_memory(len >> PAGE_SHIFT);
return -ENOMEM;
}
INIT_LIST_HEAD(&vma->anon_vma_chain);
vma->vm_mm = mm;
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_pgoff = pgoff;
vma->vm_flags = flags;
vma->vm_page_prot = vm_get_page_prot(flags);
vma_link(mm, vma, prev, rb_link, rb_parent);
out:
perf_event_mmap(vma);
mm->total_vm += len >> PAGE_SHIFT;
if (flags & VM_LOCKED)
mm->locked_vm += (len >> PAGE_SHIFT);
vma->vm_flags |= VM_SOFTDIRTY;
return addr;
}
unsigned long vm_brk(unsigned long addr, unsigned long len)
{
struct mm_struct *mm = current->mm;
unsigned long ret;
bool populate;
down_write(&mm->mmap_sem);
ret = do_brk(addr, len);
populate = ((mm->def_flags & VM_LOCKED) != 0);
up_write(&mm->mmap_sem);
if (populate)
mm_populate(addr, len);
return ret;
}
EXPORT_SYMBOL(vm_brk);
/* Release all mmaps. */
void exit_mmap(struct mm_struct *mm)
{
struct mmu_gather tlb;
struct vm_area_struct *vma;
unsigned long nr_accounted = 0;
/* mm's last user has gone, and its about to be pulled down */
mmu_notifier_release(mm);
if (mm->locked_vm) {
vma = mm->mmap;
while (vma) {
if (vma->vm_flags & VM_LOCKED)
munlock_vma_pages_all(vma);
vma = vma->vm_next;
}
}
arch_exit_mmap(mm);
vma = mm->mmap;
if (!vma) /* Can happen if dup_mmap() received an OOM */
return;
lru_add_drain();
flush_cache_mm(mm);
tlb_gather_mmu(&tlb, mm, 0, -1);
/* update_hiwater_rss(mm) here? but nobody should be looking */
/* Use -1 here to ensure all VMAs in the mm are unmapped */
unmap_vmas(&tlb, vma, 0, -1);
free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
tlb_finish_mmu(&tlb, 0, -1);
/*
* Walk the list again, actually closing and freeing it,
* with preemption enabled, without holding any MM locks.
*/
while (vma) {
if (vma->vm_flags & VM_ACCOUNT)
nr_accounted += vma_pages(vma);
vma = remove_vma(vma);
}
vm_unacct_memory(nr_accounted);
WARN_ON(atomic_long_read(&mm->nr_ptes) >
(FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT);
}
/* Insert vm structure into process list sorted by address
* and into the inode's i_mmap tree. If vm_file is non-NULL
* then i_mmap_mutex is taken here.
*/
int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
{
struct vm_area_struct *prev;
struct rb_node **rb_link, *rb_parent;
/*
* The vm_pgoff of a purely anonymous vma should be irrelevant
* until its first write fault, when page's anon_vma and index
* are set. But now set the vm_pgoff it will almost certainly
* end up with (unless mremap moves it elsewhere before that
* first wfault), so /proc/pid/maps tells a consistent story.
*
* By setting it to reflect the virtual start address of the
* vma, merges and splits can happen in a seamless way, just
* using the existing file pgoff checks and manipulations.
* Similarly in do_mmap_pgoff and in do_brk.
*/
if (!vma->vm_file) {
BUG_ON(vma->anon_vma);
vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
}
if (find_vma_links(mm, vma->vm_start, vma->vm_end,
&prev, &rb_link, &rb_parent))
return -ENOMEM;
if ((vma->vm_flags & VM_ACCOUNT) &&
security_vm_enough_memory_mm(mm, vma_pages(vma)))
return -ENOMEM;
vma_link(mm, vma, prev, rb_link, rb_parent);
return 0;
}
/*
* Copy the vma structure to a new location in the same mm,
* prior to moving page table entries, to effect an mremap move.
*/
struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
unsigned long addr, unsigned long len, pgoff_t pgoff,
bool *need_rmap_locks)
{
struct vm_area_struct *vma = *vmap;
unsigned long vma_start = vma->vm_start;
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *new_vma, *prev;
struct rb_node **rb_link, *rb_parent;
bool faulted_in_anon_vma = true;
/*
* If anonymous vma has not yet been faulted, update new pgoff
* to match new location, to increase its chance of merging.
*/
if (unlikely(!vma->vm_file && !vma->anon_vma)) {
pgoff = addr >> PAGE_SHIFT;
faulted_in_anon_vma = false;
}
if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
return NULL; /* should never get here */
new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma));
if (new_vma) {
/*
* Source vma may have been merged into new_vma
*/
if (unlikely(vma_start >= new_vma->vm_start &&
vma_start < new_vma->vm_end)) {
/*
* The only way we can get a vma_merge with
* self during an mremap is if the vma hasn't
* been faulted in yet and we were allowed to
* reset the dst vma->vm_pgoff to the
* destination address of the mremap to allow
* the merge to happen. mremap must change the
* vm_pgoff linearity between src and dst vmas
* (in turn preventing a vma_merge) to be
* safe. It is only safe to keep the vm_pgoff
* linear if there are no pages mapped yet.
*/
VM_BUG_ON(faulted_in_anon_vma);
*vmap = vma = new_vma;
}
*need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
} else {
new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
if (new_vma) {
*new_vma = *vma;
new_vma->vm_start = addr;
new_vma->vm_end = addr + len;
new_vma->vm_pgoff = pgoff;
if (vma_dup_policy(vma, new_vma))
goto out_free_vma;
INIT_LIST_HEAD(&new_vma->anon_vma_chain);
if (anon_vma_clone(new_vma, vma))
goto out_free_mempol;
if (new_vma->vm_file)
get_file(new_vma->vm_file);
if (new_vma->vm_ops && new_vma->vm_ops->open)
new_vma->vm_ops->open(new_vma);
vma_link(mm, new_vma, prev, rb_link, rb_parent);
*need_rmap_locks = false;
}
}
return new_vma;
out_free_mempol:
mpol_put(vma_policy(new_vma));
out_free_vma:
kmem_cache_free(vm_area_cachep, new_vma);
return NULL;
}
/*
* Return true if the calling process may expand its vm space by the passed
* number of pages
*/
int may_expand_vm(struct mm_struct *mm, unsigned long npages)
{
unsigned long cur = mm->total_vm; /* pages */
unsigned long lim;
lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
if (cur + npages > lim)
return 0;
return 1;
}
static int special_mapping_fault(struct vm_area_struct *vma,
struct vm_fault *vmf)
{
pgoff_t pgoff;
struct page **pages;
/*
* special mappings have no vm_file, and in that case, the mm
* uses vm_pgoff internally. So we have to subtract it from here.
* We are allowed to do this because we are the mm; do not copy
* this code into drivers!
*/
pgoff = vmf->pgoff - vma->vm_pgoff;
for (pages = vma->vm_private_data; pgoff && *pages; ++pages)
pgoff--;
if (*pages) {
struct page *page = *pages;
get_page(page);
vmf->page = page;
return 0;
}
return VM_FAULT_SIGBUS;
}
/*
* Having a close hook prevents vma merging regardless of flags.
*/
static void special_mapping_close(struct vm_area_struct *vma)
{
}
static const struct vm_operations_struct special_mapping_vmops = {
.close = special_mapping_close,
.fault = special_mapping_fault,
};
/*
* Called with mm->mmap_sem held for writing.
* Insert a new vma covering the given region, with the given flags.
* Its pages are supplied by the given array of struct page *.
* The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
* The region past the last page supplied will always produce SIGBUS.
* The array pointer and the pages it points to are assumed to stay alive
* for as long as this mapping might exist.
*/
struct vm_area_struct *_install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, struct page **pages)
{
int ret;
struct vm_area_struct *vma;
vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (unlikely(vma == NULL))
return ERR_PTR(-ENOMEM);
INIT_LIST_HEAD(&vma->anon_vma_chain);
vma->vm_mm = mm;
vma->vm_start = addr;
vma->vm_end = addr + len;
vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
vma->vm_ops = &special_mapping_vmops;
vma->vm_private_data = pages;
ret = insert_vm_struct(mm, vma);
if (ret)
goto out;
mm->total_vm += len >> PAGE_SHIFT;
perf_event_mmap(vma);
return vma;
out:
kmem_cache_free(vm_area_cachep, vma);
return ERR_PTR(ret);
}
int install_special_mapping(struct mm_struct *mm,
unsigned long addr, unsigned long len,
unsigned long vm_flags, struct page **pages)
{
struct vm_area_struct *vma = _install_special_mapping(mm,
addr, len, vm_flags, pages);
if (IS_ERR(vma))
return PTR_ERR(vma);
return 0;
}
static DEFINE_MUTEX(mm_all_locks_mutex);
static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
{
if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
/*
* The LSB of head.next can't change from under us
* because we hold the mm_all_locks_mutex.
*/
down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
/*
* We can safely modify head.next after taking the
* anon_vma->root->rwsem. If some other vma in this mm shares
* the same anon_vma we won't take it again.
*
* No need of atomic instructions here, head.next
* can't change from under us thanks to the
* anon_vma->root->rwsem.
*/
if (__test_and_set_bit(0, (unsigned long *)
&anon_vma->root->rb_root.rb_node))
BUG();
}
}
static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
{
if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
/*
* AS_MM_ALL_LOCKS can't change from under us because
* we hold the mm_all_locks_mutex.
*
* Operations on ->flags have to be atomic because
* even if AS_MM_ALL_LOCKS is stable thanks to the
* mm_all_locks_mutex, there may be other cpus
* changing other bitflags in parallel to us.
*/
if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
BUG();
mutex_lock_nest_lock(&mapping->i_mmap_mutex, &mm->mmap_sem);
}
}
/*
* This operation locks against the VM for all pte/vma/mm related
* operations that could ever happen on a certain mm. This includes
* vmtruncate, try_to_unmap, and all page faults.
*
* The caller must take the mmap_sem in write mode before calling
* mm_take_all_locks(). The caller isn't allowed to release the
* mmap_sem until mm_drop_all_locks() returns.
*
* mmap_sem in write mode is required in order to block all operations
* that could modify pagetables and free pages without need of
* altering the vma layout (for example populate_range() with
* nonlinear vmas). It's also needed in write mode to avoid new
* anon_vmas to be associated with existing vmas.
*
* A single task can't take more than one mm_take_all_locks() in a row
* or it would deadlock.
*
* The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
* mapping->flags avoid to take the same lock twice, if more than one
* vma in this mm is backed by the same anon_vma or address_space.
*
* We can take all the locks in random order because the VM code
* taking i_mmap_mutex or anon_vma->rwsem outside the mmap_sem never
* takes more than one of them in a row. Secondly we're protected
* against a concurrent mm_take_all_locks() by the mm_all_locks_mutex.
*
* mm_take_all_locks() and mm_drop_all_locks are expensive operations
* that may have to take thousand of locks.
*
* mm_take_all_locks() can fail if it's interrupted by signals.
*/
int mm_take_all_locks(struct mm_struct *mm)
{
struct vm_area_struct *vma;
struct anon_vma_chain *avc;
BUG_ON(down_read_trylock(&mm->mmap_sem));
mutex_lock(&mm_all_locks_mutex);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (signal_pending(current))
goto out_unlock;
if (vma->vm_file && vma->vm_file->f_mapping)
vm_lock_mapping(mm, vma->vm_file->f_mapping);
}
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (signal_pending(current))
goto out_unlock;
if (vma->anon_vma)
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
vm_lock_anon_vma(mm, avc->anon_vma);
}
return 0;
out_unlock:
mm_drop_all_locks(mm);
return -EINTR;
}
static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
{
if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
/*
* The LSB of head.next can't change to 0 from under
* us because we hold the mm_all_locks_mutex.
*
* We must however clear the bitflag before unlocking
* the vma so the users using the anon_vma->rb_root will
* never see our bitflag.
*
* No need of atomic instructions here, head.next
* can't change from under us until we release the
* anon_vma->root->rwsem.
*/
if (!__test_and_clear_bit(0, (unsigned long *)
&anon_vma->root->rb_root.rb_node))
BUG();
anon_vma_unlock_write(anon_vma);
}
}
static void vm_unlock_mapping(struct address_space *mapping)
{
if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
/*
* AS_MM_ALL_LOCKS can't change to 0 from under us
* because we hold the mm_all_locks_mutex.
*/
mutex_unlock(&mapping->i_mmap_mutex);
if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
&mapping->flags))
BUG();
}
}
/*
* The mmap_sem cannot be released by the caller until
* mm_drop_all_locks() returns.
*/
void mm_drop_all_locks(struct mm_struct *mm)
{
struct vm_area_struct *vma;
struct anon_vma_chain *avc;
BUG_ON(down_read_trylock(&mm->mmap_sem));
BUG_ON(!mutex_is_locked(&mm_all_locks_mutex));
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (vma->anon_vma)
list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
vm_unlock_anon_vma(avc->anon_vma);
if (vma->vm_file && vma->vm_file->f_mapping)
vm_unlock_mapping(vma->vm_file->f_mapping);
}
mutex_unlock(&mm_all_locks_mutex);
}
/*
* initialise the VMA slab
*/
void __init mmap_init(void)
{
int ret;
ret = percpu_counter_init(&vm_committed_as, 0);
VM_BUG_ON(ret);
}
/*
* Initialise sysctl_user_reserve_kbytes.
*
* This is intended to prevent a user from starting a single memory hogging
* process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
* mode.
*
* The default value is min(3% of free memory, 128MB)
* 128MB is enough to recover with sshd/login, bash, and top/kill.
*/
static int init_user_reserve(void)
{
unsigned long free_kbytes;
free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
return 0;
}
subsys_initcall(init_user_reserve);
/*
* Initialise sysctl_admin_reserve_kbytes.
*
* The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
* to log in and kill a memory hogging process.
*
* Systems with more than 256MB will reserve 8MB, enough to recover
* with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
* only reserve 3% of free pages by default.
*/
static int init_admin_reserve(void)
{
unsigned long free_kbytes;
free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
return 0;
}
subsys_initcall(init_admin_reserve);
/*
* Reinititalise user and admin reserves if memory is added or removed.
*
* The default user reserve max is 128MB, and the default max for the
* admin reserve is 8MB. These are usually, but not always, enough to
* enable recovery from a memory hogging process using login/sshd, a shell,
* and tools like top. It may make sense to increase or even disable the
* reserve depending on the existence of swap or variations in the recovery
* tools. So, the admin may have changed them.
*
* If memory is added and the reserves have been eliminated or increased above
* the default max, then we'll trust the admin.
*
* If memory is removed and there isn't enough free memory, then we
* need to reset the reserves.
*
* Otherwise keep the reserve set by the admin.
*/
static int reserve_mem_notifier(struct notifier_block *nb,
unsigned long action, void *data)
{
unsigned long tmp, free_kbytes;
switch (action) {
case MEM_ONLINE:
/* Default max is 128MB. Leave alone if modified by operator. */
tmp = sysctl_user_reserve_kbytes;
if (0 < tmp && tmp < (1UL << 17))
init_user_reserve();
/* Default max is 8MB. Leave alone if modified by operator. */
tmp = sysctl_admin_reserve_kbytes;
if (0 < tmp && tmp < (1UL << 13))
init_admin_reserve();
break;
case MEM_OFFLINE:
free_kbytes = global_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);
if (sysctl_user_reserve_kbytes > free_kbytes) {
init_user_reserve();
pr_info("vm.user_reserve_kbytes reset to %lu\n",
sysctl_user_reserve_kbytes);
}
if (sysctl_admin_reserve_kbytes > free_kbytes) {
init_admin_reserve();
pr_info("vm.admin_reserve_kbytes reset to %lu\n",
sysctl_admin_reserve_kbytes);
}
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block reserve_mem_nb = {
.notifier_call = reserve_mem_notifier,
};
static int __meminit init_reserve_notifier(void)
{
if (register_hotmemory_notifier(&reserve_mem_nb))
printk("Failed registering memory add/remove notifier for admin reserve");
return 0;
}
subsys_initcall(init_reserve_notifier);
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