freeze_bdev: don't deactivate successfully frozen MS_RDONLY sb
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>
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1 changed files with 4 additions and 3 deletions
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@ -246,7 +246,8 @@ struct super_block *freeze_bdev(struct block_device *bdev)
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if (!sb)
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goto out;
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if (sb->s_flags & MS_RDONLY) {
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deactivate_locked_super(sb);
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sb->s_frozen = SB_FREEZE_TRANS;
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up_write(&sb->s_umount);
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mutex_unlock(&bdev->bd_fsfreeze_mutex);
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return sb;
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}
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@ -307,7 +308,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
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BUG_ON(sb->s_bdev != bdev);
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down_write(&sb->s_umount);
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if (sb->s_flags & MS_RDONLY)
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goto out_deactivate;
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goto out_unfrozen;
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if (sb->s_op->unfreeze_fs) {
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error = sb->s_op->unfreeze_fs(sb);
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@ -321,11 +322,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb)
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}
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}
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out_unfrozen:
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sb->s_frozen = SB_UNFROZEN;
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smp_wmb();
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wake_up(&sb->s_wait_unfrozen);
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out_deactivate:
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if (sb)
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deactivate_locked_super(sb);
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out_unlock:
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