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Commit 8edd64bd authored by Al Viro's avatar Al Viro
Browse files

get rid of restarts in sync_filesystems() 



At the same time we can kill s_need_restart and local mutex in there.
__put_super() made public for a while; will be gone later.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 551de6f3

fs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -130,7 +130,7 @@ static inline void destroy_super(struct super_block *s) 
 * Drop a superblock's refcount.  Returns non-zero if the superblock was

 * destroyed.  The caller must hold sb_lock.

 */

static int __put_super(struct super_block *sb)

int __put_super(struct super_block *sb)

{

	int ret = 0;

fs/sync.c

+3 −25
Original line number Diff line number Diff line
@@ -80,35 +80,15 @@ EXPORT_SYMBOL_GPL(sync_filesystem); 
/*

 * Sync all the data for all the filesystems (called by sys_sync() and

 * emergency sync)

 *

 * This operation is careful to avoid the livelock which could easily happen

 * if two or more filesystems are being continuously dirtied.  s_need_sync

 * is used only here.  We set it against all filesystems and then clear it as

 * we sync them.  So redirtied filesystems are skipped.

 *

 * But if process A is currently running sync_filesystems and then process B

 * calls sync_filesystems as well, process B will set all the s_need_sync

 * flags again, which will cause process A to resync everything.  Fix that with

 * a local mutex.

 */

static void sync_filesystems(int wait)

{

	struct super_block *sb;

	static DEFINE_MUTEX(mutex);

	struct super_block *sb, *n;



	mutex_lock(&mutex);		/* Could be down_interruptible */

	spin_lock(&sb_lock);

	list_for_each_entry(sb, &super_blocks, s_list)

		if (!list_empty(&sb->s_instances))

			sb->s_need_sync = 1;



restart:

	list_for_each_entry(sb, &super_blocks, s_list) {

	list_for_each_entry_safe(sb, n, &super_blocks, s_list) {

		if (list_empty(&sb->s_instances))

			continue;

		if (!sb->s_need_sync)

			continue;

		sb->s_need_sync = 0;

		sb->s_count++;

		spin_unlock(&sb_lock);
@@ -119,11 +99,9 @@ static void sync_filesystems(int wait) 


		/* restart only when sb is no longer on the list */

		spin_lock(&sb_lock);

		if (__put_super_and_need_restart(sb))

			goto restart;

		__put_super(sb);

	}

	spin_unlock(&sb_lock);

	mutex_unlock(&mutex);

}



/*

include/linux/fs.h

+1 −1
Original line number Diff line number Diff line
@@ -1332,7 +1332,6 @@ struct super_block { 
	struct rw_semaphore	s_umount;

	struct mutex		s_lock;

	int			s_count;

	int			s_need_sync;

	atomic_t		s_active;

#ifdef CONFIG_SECURITY

	void                    *s_security;
@@ -1780,6 +1779,7 @@ extern int get_sb_pseudo(struct file_system_type *, char *, 
	struct vfsmount *mnt);

extern void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb);

int __put_super_and_need_restart(struct super_block *sb);

int __put_super(struct super_block *sb);

void put_super(struct super_block *sb);



/* Alas, no aliases. Too much hassle with bringing module.h everywhere */