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Commit 856bf4d7 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
Browse files

fs: sys_sync fix 



s_syncing livelock avoidance was breaking data integrity guarantee of
sys_sync, by allowing sys_sync to skip writing or waiting for superblocks
if there is a concurrent sys_sync happening.

This livelock avoidance is much less important now that we don't have the
get_super_to_sync() call after every sb that we sync.  This was replaced
by __put_super_and_need_restart.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 38f21977

fs/fs-writeback.c

+1 −19
Original line number Original line Diff line number Diff line
@@ -652,18 +652,6 @@ void sync_inodes_sb(struct super_block *sb, int wait) 
	sync_sb_inodes(sb, &wbc);

	sync_sb_inodes(sb, &wbc);

}

}





/*

 * Rather lame livelock avoidance.

 */

static void set_sb_syncing(int val)

{

	struct super_block *sb;

	spin_lock(&sb_lock);

	list_for_each_entry_reverse(sb, &super_blocks, s_list)

		sb->s_syncing = val;

	spin_unlock(&sb_lock);

}



/**

/**

 * sync_inodes - writes all inodes to disk

 * sync_inodes - writes all inodes to disk

 * @wait: wait for completion

 * @wait: wait for completion
@@ -690,9 +678,6 @@ static void __sync_inodes(int wait) 
	spin_lock(&sb_lock);

	spin_lock(&sb_lock);

restart:

restart:

	list_for_each_entry(sb, &super_blocks, s_list) {

	list_for_each_entry(sb, &super_blocks, s_list) {

		if (sb->s_syncing)

			continue;

		sb->s_syncing = 1;

		sb->s_count++;

		sb->s_count++;

		spin_unlock(&sb_lock);

		spin_unlock(&sb_lock);

		down_read(&sb->s_umount);

		down_read(&sb->s_umount);
@@ -710,14 +695,11 @@ restart: 




void sync_inodes(int wait)

void sync_inodes(int wait)

{

{

	set_sb_syncing(0);

	__sync_inodes(0);

	__sync_inodes(0);





	if (wait) {

	if (wait)

		set_sb_syncing(0);

		__sync_inodes(1);

		__sync_inodes(1);

}

}

}





/**

/**

 * write_inode_now	-	write an inode to disk

 * write_inode_now	-	write an inode to disk

include/linux/fs.h

+0 −1
Original line number Original line Diff line number Diff line
@@ -1133,7 +1133,6 @@ struct super_block { 
	struct rw_semaphore	s_umount;

	struct rw_semaphore	s_umount;

	struct mutex		s_lock;

	struct mutex		s_lock;

	int			s_count;

	int			s_count;

	int			s_syncing;

	int			s_need_sync_fs;

	int			s_need_sync_fs;

	atomic_t		s_active;

	atomic_t		s_active;

#ifdef CONFIG_SECURITY

#ifdef CONFIG_SECURITY