[PATCHv5 12/16] ext4: fix race condition in marking SB dirty
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From: Artem Bityutskiy on 6 Jun 2010 11:00 From: Artem Bityutskiy <Artem.Bityutskiy(a)nokia.com> When synchronizing the superblock, ext4 first starts changing the SB (a) and then marks the superblock as clean (b). However, meanwhile (between (a) and (b)) someone else can modify the superblock and mark it as dirty. This would be a race condition, and the result would be that we'd end up with a modified superblock which would nevertheless be marked as clean (because of (b)). This means that 'sync_supers()' would never call our '->write_super()', at least not until yet another SB change happens. This patch fixes this race condition by marking the superblock as clean before starting SB changes. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy(a)nokia.com> Cc: linux-ext4(a)vger.kernel.org Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy(a)nokia.com> --- fs/ext4/super.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index d1707a0..7b19932 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3372,6 +3372,7 @@ static int ext4_commit_super(struct super_block *sb, int sync) clear_buffer_write_io_error(sbh); set_buffer_uptodate(sbh); } + sb_mark_clean(sb); /* * If the file system is mounted read-only, don't update the * superblock write time. This avoids updating the superblock @@ -3392,7 +3393,6 @@ static int ext4_commit_super(struct super_block *sb, int sync) &EXT4_SB(sb)->s_freeblocks_counter)); es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive( &EXT4_SB(sb)->s_freeinodes_counter)); - sb_mark_clean(sb); BUFFER_TRACE(sbh, "marking dirty"); mark_buffer_dirty(sbh); if (sync) { -- 1.7.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |