No need to mess with ->d_op at all. Note that ->d_delete that always
returns 1 is equivalent to having DCACHE_DONTCACHE in ->d_flags.
Later the same thing will be placed into ->s_d_flags of the filesystems
where we want that behaviour for all dentries; then the check in
simple_lookup() will at least get unlikely() slapped on it.
NOTE: there are only two filesystems where
* simple_lookup() might be called
* default ->d_op is non-NULL
* its ->d_delete() doesn't always return 1
If not for those, we could have simple_lookup() just set DCACHE_DONTCACHE
without even looking at ->d_op. Filesystems in question are btrfs
(where ->d_delete() takes care to recognize the dentries that might
come from simple_lookup() and returns 1 for those) and tracefs.
The former would be fine with simple_lookup() setting DCACHE_DONTCACHE;
the latter... probably wants DCACHE_DONTCACHE in default d_flags.
IOW, we might want to drop the check for ->d_op in simple_lookup();
it's definitely a separate story, though.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/libfs.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index ab82de070310..19cc12651708 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -75,9 +75,11 @@ struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, unsigned
{
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
- if (!dentry->d_op)
- d_set_d_op(dentry, &simple_dentry_operations);
-
+ if (!dentry->d_op && !(dentry->d_flags & DCACHE_DONTCACHE)) {
+ spin_lock(&dentry->d_lock);
+ dentry->d_flags |= DCACHE_DONTCACHE;
+ spin_unlock(&dentry->d_lock);
+ }
if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir))
return NULL;
--
2.39.5
