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

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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: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2024-05-07 14:12:13 -04:00 committed by David Sterba
parent 1f9d44c0a1
commit b8ccef0483
1 changed files with 23 additions and 5 deletions
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28
fs/btrfs/extent-tree.c
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@ -5350,7 +5350,15 @@ 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 we don't need to visit this node don't reada. */
if (!visit_node_for_delete(root, wc, eb, refs, flags, slot))
@ -5399,7 +5407,11 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
NULL);
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) {
@ -5654,8 +5666,9 @@ 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;
}
wc->lookup_info = 0;
@ -5766,7 +5779,12 @@ 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;