[PATCH] kernfs: avoid iattr allocation in listxattr

[PATCH] kernfs: avoid iattr allocation in listxattr

[Yichong Chen]

kernfs_iop_listxattr() only needs to report existing xattrs, but it uses
kernfs_iattrs(), which allocates kernfs_iattrs when the node does not
have one yet.

This makes a query operation create persistent per-node metadata even
when the xattr list is empty.

Use kernfs_iattrs_noalloc() instead and return an empty list when no
iattrs exist.

Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
---
 fs/kernfs/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 2cb20294aaf5..237dcdd73fc2 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -141,9 +141,9 @@ ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
 	struct kernfs_iattrs *attrs;
 
-	attrs = kernfs_iattrs(kn);
+	attrs = kernfs_iattrs_noalloc(kn);
 	if (!attrs)
-		return -ENOMEM;
+		return 0;
 
 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
 }
-- 
2.51.0

Re: [PATCH] kernfs: avoid iattr allocation in listxattr

[Tejun Heo]

On Fri, Jul 31, 2026 at 08:05:54PM +0800, Yichong Chen wrote:
> kernfs_iop_listxattr() only needs to report existing xattrs, but it uses
> kernfs_iattrs(), which allocates kernfs_iattrs when the node does not
> have one yet.
> 
> This makes a query operation create persistent per-node metadata even
> when the xattr list is empty.
> 
> Use kernfs_iattrs_noalloc() instead and return an empty list when no
> iattrs exist.
> 
> Signed-off-by: Yichong Chen <chenyichong@uniontech.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun