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Commit c847b28a authored by Josef Bacik's avatar Josef Bacik Committed by Greg Kroah-Hartman
Browse files

btrfs: clean up our handling of refs == 0 in snapshot delete 



[ Upstream commit b8ccef048354074a548f108e51d0557d6adfd3a3 ]

In reada we BUG_ON(refs == 0), which could be unkind since we aren't
holding a lock on the extent leaf and thus could get a transient
incorrect answer.  In walk_down_proc we also BUG_ON(refs == 0), which
could happen if we have extent tree corruption.  Change that to return
-EUCLEAN.  In do_walk_down() we catch this case and handle it correctly,
however we return -EIO, which -EUCLEAN is a more appropriate error code.
Finally in walk_up_proc we have the same BUG_ON(refs == 0), so convert
that to proper error handling.  Also adjust the error message so we can
actually do something with the information.

Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 2df0e486

fs/btrfs/extent-tree.c

+23 −5
Original line number Diff line number Diff line
@@ -8409,7 +8409,15 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans, 
		/* We don't care about errors in readahead. */

		if (ret < 0)

			continue;

		BUG_ON(refs == 0);



		/*

		 * This could be racey, it's conceivable that we raced and end

		 * up with a bogus refs count, if that's the case just skip, if

		 * we are actually corrupt we will notice when we look up

		 * everything again with our locks.

		 */

		if (refs == 0)

			continue;



		if (wc->stage == DROP_REFERENCE) {

			if (refs == 1)
@@ -8476,7 +8484,11 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans, 
		BUG_ON(ret == -ENOMEM);

		if (ret)

			return ret;

		BUG_ON(wc->refs[level] == 0);

		if (unlikely(wc->refs[level] == 0)) {

			btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",

				  eb->start);

			return -EUCLEAN;

		}

	}



	if (wc->stage == DROP_REFERENCE) {
@@ -8584,8 +8596,9 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans, 
		goto out_unlock;



	if (unlikely(wc->refs[level - 1] == 0)) {

		btrfs_err(fs_info, "Missing references.");

		ret = -EIO;

		btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",

			  bytenr);

		ret = -EUCLEAN;

		goto out_unlock;

	}

	*lookup_info = 0;
@@ -8753,7 +8766,12 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans, 
				path->locks[level] = 0;

				return ret;

			}

			BUG_ON(wc->refs[level] == 0);

			if (unlikely(wc->refs[level] == 0)) {

				btrfs_tree_unlock_rw(eb, path->locks[level]);

				btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",

					  eb->start);

				return -EUCLEAN;

			}

			if (wc->refs[level] == 1) {

				btrfs_tree_unlock_rw(eb, path->locks[level]);

				path->locks[level] = 0;