[PATCH] xfs: return -ENOENT for unallocated inodes in xfs_imap_lookup

[Hans Holmberg <hans.holmberg@wdc.com>]

Under heavy garbage collection pressure from RocksDB workloads,
filesystem shutdowns can occur in xfs_zone_gc_iter_irec when
xfs_iget() returns -EINVAL.

xfs_zone_gc_iter_irec expects -ENOENT when garbage collection races
with file deletion, so that blocks belonging to deleted files can be
skipped gracefully. Returning -EINVAL instead causes the GC code to
treat this as a fatal error and forces a shutdown.

Fix this by returning -ENOENT from xfs_imap_lookup for untrusted inodes
when the inode has been deleted, allowing zone GC to safely ignore stale
mappings.

Fixes: 080d01c41d44 ("xfs: implement zoned garbage collection")
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
---

We could also fix this up in xfs_zone_gc_iter_irec, and handle -EINVAL
as a non-fatal error, but returning -ENOENT from xfs_imap_lookup seems
like the more right thing to do.

The check "that the returned record contains the required inode" in
xfs_imap_lookup also returns -EINVAL and might be worth switching
over to -ENOENT but I'm leaving that as is I did not hit that case
in my testing.

 fs/xfs/libxfs/xfs_ialloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index dcef06ec0a02..702e1e853e45 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -2442,7 +2442,7 @@ xfs_imap_lookup(
 	/* for untrusted inodes check it is allocated first */
 	if ((flags & XFS_IGET_UNTRUSTED) &&
 	    (rec.ir_free & XFS_INOBT_MASK(agino - rec.ir_startino)))
-		return -EINVAL;
+		return -ENOENT;
 
 	*chunk_agbno = XFS_AGINO_TO_AGBNO(mp, rec.ir_startino);
 	*offset_agbno = agbno - *chunk_agbno;
-- 
2.34.1