Commit f1282c84 authored by Neil Brown's avatar Neil Brown Committed by Greg Kroah-Hartman
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sysfs: Support sysfs_notify from atomic context with new sysfs_notify_dirent 



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: default avatarNeil Brown <neilb@suse.de>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ec748fa9

fs/sysfs/dir.c

+1 −0
Original line number Diff line number Diff line
@@ -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)

fs/sysfs/file.c

+18 −13
Original line number Diff line number Diff line
@@ -453,17 +453,8 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait) 
	return POLLERR|POLLPRI;

}



void sysfs_notify(struct kobject *k, char *dir, char *attr)

void sysfs_notify_dirent(struct sysfs_dirent *sd)

{

	struct sysfs_dirent *sd = k->sd;



	mutex_lock(&sysfs_mutex);



	if (sd && dir)

		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);
@@ -476,6 +467,20 @@ void sysfs_notify(struct kobject *k, char *dir, char *attr) 


	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;



	mutex_lock(&sysfs_mutex);



	if (sd && dir)

		sd = sysfs_find_dirent(sd, dir);

	if (sd && attr)

		sd = sysfs_find_dirent(sd, attr);

	if (sd)

		sysfs_notify_dirent(sd);



	mutex_unlock(&sysfs_mutex);

}

fs/sysfs/mount.c

+15 −0
Original line number Diff line number Diff line
@@ -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 @@ out_err: 
	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);

fs/sysfs/sysfs.h

+4 −2
Original line number Diff line number Diff line
@@ -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

include/linux/sysfs.h

+24 −3
Original line number Diff line number Diff line
@@ -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)

{

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