[PATCH v4] btrfs: improve error reporting in lookup_inline_extent_backref

[Nikolay Borisov <nborisov@suse.com>]

When iterating the backrefs in an extent item if the ptr to the
'current' backref record goes beyond the extent item a warning is
generated and -ENOENT is returned. However what's more appropriate to
debug such cases would be to return EUCLEAN and also print identifying
information about the performed search as well as the current content of
the leaf containing the possibly corrupted extent item.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---

V4:
 * Also print the value of 'parent' as it's pertinent when metadata inline backrefs
 are being searched (Filipe)
 * Print the leaf before printing the error message so that the latter is
 not lost (Filipe)

V3:
 * Fixed format for the btree slot
 * Removed redundant argument passed to format string

 fs/btrfs/extent-tree.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 963160a0c393..cae2ef560f3f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -895,7 +895,14 @@ int lookup_inline_extent_backref(struct btrfs_trans_handle *trans,
 	err = -ENOENT;
 	while (1) {
 		if (ptr >= end) {
-			WARN_ON(ptr > end);
+			if (ptr > end) {
+				err = -EUCLEAN;
+				btrfs_print_leaf(path->nodes[0]);
+				btrfs_crit(fs_info,
+"overrun extent record at slot %d [%llu BTRFS_EXTENT_ITEM_KEY %llu] while looking for inline extent for root %llu owner %llu offset %llu parent %llu",
+				path->slots[0], bytenr, num_bytes,
+				root_objectid, owner, offset, parent);
+			}
 			break;
 		}
 		iref = (struct btrfs_extent_inline_ref *)ptr;
--
2.25.1