From: Josef Bacik <josef@toxicpanda.com>
To: linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH v3 12/15] btrfs: clean up our handling of refs == 0 in snapshot delete
Date: Tue, 7 May 2024 14:12:13 -0400 [thread overview]
Message-ID: <874b3cb1c1591a96572a32d27b80b205cee4b795.1715105406.git.josef@toxicpanda.com> (raw)
In-Reply-To: <cover.1715105406.git.josef@toxicpanda.com>
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>
---
fs/btrfs/extent-tree.c | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index c75a5b3ddb8f..2e3a2aba8001 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5351,7 +5351,15 @@ 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))
@@ -5400,7 +5408,12 @@ 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) {
@@ -5663,8 +5676,9 @@ 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;
@@ -5775,7 +5789,13 @@ 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;
--
2.43.0
next prev parent reply other threads:[~2024-05-07 18:12 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 18:12 [PATCH v3 00/15] btrfs: snapshot delete cleanups Josef Bacik
2024-05-07 18:12 ` [PATCH v3 01/15] btrfs: don't do find_extent_buffer in do_walk_down Josef Bacik
2024-05-07 18:12 ` [PATCH v3 02/15] btrfs: remove all extra btrfs_check_eb_owner() calls Josef Bacik
2024-05-07 20:39 ` Qu Wenruo
2024-05-07 18:12 ` [PATCH v3 03/15] btrfs: use btrfs_read_extent_buffer in do_walk_down Josef Bacik
2024-05-07 18:12 ` [PATCH v3 04/15] btrfs: push lookup_info into walk_control Josef Bacik
2024-05-07 18:12 ` [PATCH v3 05/15] btrfs: move the eb uptodate code into it's own helper Josef Bacik
2024-05-07 18:12 ` [PATCH v3 06/15] btrfs: remove need_account in do_walk_down Josef Bacik
2024-05-07 18:12 ` [PATCH v3 07/15] btrfs: unify logic to decide if we need to walk down into a node Josef Bacik
2024-05-07 18:12 ` [PATCH v3 08/15] btrfs: extract the reference dropping code into it's own helper Josef Bacik
2024-05-07 18:12 ` [PATCH v3 09/15] btrfs: don't BUG_ON ENOMEM in walk_down_proc Josef Bacik
2024-05-07 18:12 ` [PATCH v3 10/15] btrfs: handle errors from ref mods during UPDATE_BACKREF Josef Bacik
2024-05-07 18:12 ` [PATCH v3 11/15] btrfs: replace BUG_ON with ASSERT in walk_down_proc Josef Bacik
2024-05-07 18:12 ` Josef Bacik [this message]
2024-05-07 18:12 ` [PATCH v3 13/15] btrfs: convert correctness BUG_ON()'s to ASSERT()'s in walk_up_proc Josef Bacik
2024-05-07 18:12 ` [PATCH v3 14/15] btrfs: handle errors from btrfs_dec_ref properly Josef Bacik
2024-05-07 18:12 ` [PATCH v3 15/15] btrfs: add documentation around snapshot delete Josef Bacik
2024-05-15 18:18 ` [PATCH v3 00/15] btrfs: snapshot delete cleanups David Sterba
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