Messages in this thread Patch in this message | | | Date | Fri, 29 Jan 2010 09:56:22 +0900 | From | "Jun'ichi Nomura" <> | Subject | [BUGFIX] [PATCH] freeze_bdev: don't deactivate successfully frozen MS_RDONLY sb |
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Thanks Thomas and Christoph for testing and review. I removed 'smp_wmb()' before up_write from the previous patch, since up_write() should have necessary ordering constraints. (I.e. the change of s_frozen is visible to others after up_write) I'm quite sure the change is harmless but if you are uncomfortable with Tested-by/Reviewed-by on the modified patch, please remove them.
If MS_RDONLY, freeze_bdev should just up_write(s_umount) instead of deactivate_locked_super(). Also, keep sb->s_frozen consistent so that remount can check the frozen state.
Otherwise a crash reported here can happen: http://lkml.org/lkml/2010/1/16/37 http://lkml.org/lkml/2010/1/28/53
This patch should be applied for 2.6.32 stable series, too.
Reviewed-by: Christoph Hellwig <hch@lst.de> Tested-by: Thomas Backlund <tmb@mandriva.org> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: stable@kernel.org
diff --git a/fs/block_dev.c b/fs/block_dev.c index 73d6a73..d11d028 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -246,7 +246,8 @@ struct super_block *freeze_bdev(struct block_device *bdev) if (!sb) goto out; if (sb->s_flags & MS_RDONLY) { - deactivate_locked_super(sb); + sb->s_frozen = SB_FREEZE_TRANS; + up_write(&sb->s_umount); mutex_unlock(&bdev->bd_fsfreeze_mutex); return sb; } @@ -307,7 +308,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb) BUG_ON(sb->s_bdev != bdev); down_write(&sb->s_umount); if (sb->s_flags & MS_RDONLY) - goto out_deactivate; + goto out_unfrozen; if (sb->s_op->unfreeze_fs) { error = sb->s_op->unfreeze_fs(sb); @@ -321,11 +322,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb) } } +out_unfrozen: sb->s_frozen = SB_UNFROZEN; smp_wmb(); wake_up(&sb->s_wait_unfrozen); -out_deactivate: if (sb) deactivate_locked_super(sb); out_unlock:
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