From a97dc087da06b69ae976765d59810ca705e8dae1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 23 Feb 2025 20:04:30 -0500 Subject: [PATCH] simple_lookup(): just set DCACHE_DONTCACHE 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 and tracefs; both have ->d_delete() returning 1 on anything fed to simple_lookup(), so both would be fine with simple_lookup() setting DCACHE_DONTCACHE regardless of ->d_op. IOW, we might want to drop the check for ->d_op in simple_lookup(); it's definitely a separate story, though. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- fs/libfs.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/libfs.c b/fs/libfs.c index ab82de070310b..19cc126517088 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; -- 2.47.2