freeze_bdev: don't deactivate successfully frozen MS_RDONLY sb (4b06e5b9) · Commits · 戴 / test

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 Signed-off-by:

Al Viro <viro@zeniv.linux.org.uk>

fs/block_dev.c

+4 −3

Original line number	Original line	Diff line number	Diff line
	@@ -246,7 +246,8 @@ struct super_block freeze_bdev(struct block_device bdev)
	if (!sb)		if (!sb)
	goto out;		goto out;
	if (sb->s_flags & MS_RDONLY) {		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);		mutex_unlock(&bdev->bd_fsfreeze_mutex);
	return sb;		return sb;
	}		}
	@@ -307,7 +308,7 @@ int thaw_bdev(struct block_device bdev, struct super_block sb)
	BUG_ON(sb->s_bdev != bdev);		BUG_ON(sb->s_bdev != bdev);
	down_write(&sb->s_umount);		down_write(&sb->s_umount);
	if (sb->s_flags & MS_RDONLY)		if (sb->s_flags & MS_RDONLY)
	goto out_deactivate;		goto out_unfrozen;

	if (sb->s_op->unfreeze_fs) {		if (sb->s_op->unfreeze_fs) {
	error = sb->s_op->unfreeze_fs(sb);		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;		sb->s_frozen = SB_UNFROZEN;
	smp_wmb();		smp_wmb();
	wake_up(&sb->s_wait_unfrozen);		wake_up(&sb->s_wait_unfrozen);

	out_deactivate:
	if (sb)		if (sb)
	deactivate_locked_super(sb);		deactivate_locked_super(sb);
	out_unlock:		out_unlock:

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