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fs: sys_sync fix

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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: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nick Piggin 2009-01-06 14:40:26 -08:00 committed by Linus Torvalds
parent 38f2197766
commit 856bf4d717
2 changed files with 1 additions and 20 deletions
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20
fs/fs-writeback.c
View file

@ -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);
@ -710,13 +695,10 @@ 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);
}
} }
/** /**

1
include/linux/fs.h
View file

@ -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