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sysfs: Support sysfs_notify from atomic context with new sysfs_notify_dirent

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Support sysfs_notify from atomic context with new sysfs_notify_dirent

sysfs_notify currently takes sysfs_mutex.
This means that it cannot be called in atomic context.
sysfs_mutex  is sometimes held over a malloc (sysfs_rename_dir)
so it can block on low memory.

In md I want to be able to notify on a sysfs attribute from
atomic context, and I don't want to block on low memory because I
could be in the writeout path for freeing memory.

So:
 - export the "sysfs_dirent" structure along with sysfs_get, sysfs_put
   and sysfs_get_dirent so I can get the sysfs_dirent that I want to
   notify on and hold it in an md structure.
 - split sysfs_notify_dirent out of sysfs_notify so the sysfs_dirent
   can be notified on with no blocking (just a spinlock).

Signed-off-by: Neil Brown <neilb@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Neil Brown 2008-07-16 08:58:04 +10:00 committed by Greg Kroah-Hartman
parent ec748fa9ed
commit f1282c844e
5 changed files with 62 additions and 18 deletions
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1
fs/sysfs/dir.c
View file

@ -636,6 +636,7 @@ struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
return sd;
}
EXPORT_SYMBOL_GPL(sysfs_get_dirent);
static int create_dir(struct kobject *kobj, struct sysfs_dirent *parent_sd,
const char *name, struct sysfs_dirent **p_sd)

31
fs/sysfs/file.c
View file

@ -453,6 +453,22 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
return POLLERR|POLLPRI;
}
void sysfs_notify_dirent(struct sysfs_dirent *sd)
{
struct sysfs_open_dirent *od;
spin_lock(&sysfs_open_dirent_lock);
od = sd->s_attr.open;
if (od) {
atomic_inc(&od->event);
wake_up_interruptible(&od->poll);
}
spin_unlock(&sysfs_open_dirent_lock);
}
EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
void sysfs_notify(struct kobject *k, char *dir, char *attr)
{
struct sysfs_dirent *sd = k->sd;
@ -463,19 +479,8 @@ void sysfs_notify(struct kobject *k, char *dir, char *attr)
sd = sysfs_find_dirent(sd, dir);
if (sd && attr)
sd = sysfs_find_dirent(sd, attr);
if (sd) {
struct sysfs_open_dirent *od;
spin_lock(&sysfs_open_dirent_lock);
od = sd->s_attr.open;
if (od) {
atomic_inc(&od->event);
wake_up_interruptible(&od->poll);
}
spin_unlock(&sysfs_open_dirent_lock);
}
if (sd)
sysfs_notify_dirent(sd);
mutex_unlock(&sysfs_mutex);
}

15
fs/sysfs/mount.c
View file

@ -16,6 +16,7 @@
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/module.h>
#include "sysfs.h"
@ -115,3 +116,17 @@ int __init sysfs_init(void)
sysfs_dir_cachep = NULL;
goto out;
}
#undef sysfs_get
struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
{
return __sysfs_get(sd);
}
EXPORT_SYMBOL_GPL(sysfs_get);
#undef sysfs_put
void sysfs_put(struct sysfs_dirent *sd)
{
__sysfs_put(sd);
}
EXPORT_SYMBOL_GPL(sysfs_put);

6
fs/sysfs/sysfs.h
View file

@ -124,7 +124,7 @@ int sysfs_create_subdir(struct kobject *kobj, const char *name,
struct sysfs_dirent **p_sd);
void sysfs_remove_subdir(struct sysfs_dirent *sd);
static inline struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
static inline struct sysfs_dirent *__sysfs_get(struct sysfs_dirent *sd)
{
if (sd) {
WARN_ON(!atomic_read(&sd->s_count));
@ -132,12 +132,14 @@ static inline struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
}
return sd;
}
#define sysfs_get(sd) __sysfs_get(sd)
static inline void sysfs_put(struct sysfs_dirent *sd)
static inline void __sysfs_put(struct sysfs_dirent *sd)
{
if (sd && atomic_dec_and_test(&sd->s_count))
release_sysfs_dirent(sd);
}
#define sysfs_put(sd) __sysfs_put(sd)
/*
* inode.c

27
include/linux/sysfs.h
View file

@ -78,6 +78,8 @@ struct sysfs_ops {
ssize_t (*store)(struct kobject *,struct attribute *,const char *, size_t);
};
struct sysfs_dirent;
#ifdef CONFIG_SYSFS
int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
@ -118,10 +120,13 @@ void sysfs_remove_file_from_group(struct kobject *kobj,
const struct attribute *attr, const char *group);
void sysfs_notify(struct kobject *kobj, char *dir, char *attr);
void sysfs_notify_dirent(struct sysfs_dirent *sd);
struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
const unsigned char *name);
struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd);
void sysfs_put(struct sysfs_dirent *sd);
void sysfs_printk_last_file(void);
extern int __must_check sysfs_init(void);
int __must_check sysfs_init(void);
#else /* CONFIG_SYSFS */
@ -227,6 +232,22 @@ static inline void sysfs_remove_file_from_group(struct kobject *kobj,
static inline void sysfs_notify(struct kobject *kobj, char *dir, char *attr)
{
}
static inline void sysfs_notify_dirent(struct sysfs_dirent *sd)
{
}
static inline
struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
const unsigned char *name)
{
return NULL;
}
static inline struct sysfs_dirent *sysfs_get(struct sysfs_dirent *sd)
{
return NULL;
}
static inline void sysfs_put(struct sysfs_dirent *sd)
{
}
static inline int __must_check sysfs_init(void)
{