ceph: do not cache negative dentries for snapped directories

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When a LOOKUP/LOOKUPSNAP in a snapped directory returns ENOENT
without a trace, ceph_finish_lookup() creates a negative dentry
via d_add(dentry, NULL).  For live directories this is fine — the
dentry naturally expires.  But for snapped directories,
ceph_d_revalidate() unconditionally trusts all cached dentries
(valid = 1), so a negative dentry created by a transient error
persists forever, hiding entries that genuinely exist in the
snapshot.

Only cache negative dentries for live (non-snapshotted) parent
directories.  For snapped parents, skip the negative dentry so
that VFS retries the lookup on the next access.  Since the
conditions that trigger a negative dentry (MDS transient error,
local ENOENT shortcut, or MDS null dentry lease) are all rare in
snapped directories, the performance impact of this change is
negligible.

Link: https://tracker.ceph.com/issues/78529
Reported-by: Andras Pataki <apataki@flatironinstitute.org>
Signed-off-by: Xiubo Li <xiubo.li@clyso.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

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Xiubo Li 2026-07-23 14:28:19 +08:00 • committed by Ilya Dryomov

parent 699411a353

commit af59562a5b

2 changed files with 10 additions and 3 deletions

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10

fs/ceph/dir.c

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3

fs/ceph/inode.c

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