On Fri, Feb 27, 2026 at 04:00:37PM +0100, Jan Kara wrote:

On Mon 16-02-26 14:32:00, Christian Brauner wrote:

quoted

Adapt kernfs to use the rhashtable-based xattr path and switch from an
embedded struct to pointer-based lazy allocation.

Change kernfs_iattrs.xattrs from embedded 'struct simple_xattrs' to a
pointer 'struct simple_xattrs *', initialized to NULL (zeroed by
kmem_cache_zalloc). Since kernfs_iattrs is already lazily allocated
itself, this adds a second level of lazy allocation specifically for
the xattr store.

The xattr store is allocated on first setxattr. Read paths
check for NULL and return -ENODATA or empty list.

Replaced xattr entries are freed via simple_xattr_free_rcu() to allow
concurrent RCU readers to finish.

The cleanup paths in kernfs_free_rcu() and __kernfs_new_node() error
handling conditionally free the xattr store only when allocated.

Signed-off-by: Christian Brauner <brauner@kernel.org>

...

quoted

@@ -584,6 +582,12 @@ void kernfs_put(struct kernfs_node *kn)
 	if (kernfs_type(kn) == KERNFS_LINK)
 		kernfs_put(kn->symlink.target_kn);
 
+	if (kn->iattr && kn->iattr->xattrs) {
+		simple_xattrs_free(kn->iattr->xattrs, NULL);
+		kfree(kn->iattr->xattrs);
+		kn->iattr->xattrs = NULL;
+	}
+
 	spin_lock(&root->kernfs_idr_lock);
 	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
 	spin_unlock(&root->kernfs_idr_lock);

This is a slight change in the lifetime rules because previously kernfs
xattrs could be safely accessed only under RCU but after this change you
have to hold inode reference *and* RCU to safely access them. I don't think
anybody would be accessing xattrs without holding inode reference so this
should be safe but it would be good to mention this in the changelog.

Done.