Re: [PATCH 09/14] xattr: move user limits for xattrs to generic infra

[Christian Brauner <brauner@kernel.org>]

On Fri, Feb 20, 2026 at 04:03:26PM -0800, Darrick J. Wong wrote:
> On Mon, Feb 16, 2026 at 02:32:05PM +0100, Christian Brauner wrote:
> > Signed-off-by: Christian Brauner <brauner@kernel.org>
> > ---
> >  fs/kernfs/inode.c           | 75 ++-------------------------------------------
> >  fs/kernfs/kernfs-internal.h |  3 +-
> >  fs/xattr.c                  | 65 +++++++++++++++++++++++++++++++++++++++
> >  include/linux/kernfs.h      |  2 --
> >  include/linux/xattr.h       | 18 +++++++++++
> >  5 files changed, 87 insertions(+), 76 deletions(-)
> > 
> 
> I know you're just moving code around and that looks ok, but:
> 
> > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> > index b5a5f32fdfd1..d8f57f0af5e4 100644
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -99,8 +99,6 @@ enum kernfs_node_type {
> >  
> >  #define KERNFS_TYPE_MASK		0x000f
> >  #define KERNFS_FLAG_MASK		~KERNFS_TYPE_MASK
> > -#define KERNFS_MAX_USER_XATTRS		128
> > -#define KERNFS_USER_XATTR_SIZE_LIMIT	(128 << 10)
> 
> I guess this means you can't have more than 128 xattrs total, and
> sum(values) must be less than 128k?  The fixed limit is a little odd,
> but it's all pinned kernel memory, right?

Yeah, it's all pinned kernel memory.

> (IOWs, you haven't done anything wild ala xfile.c to make it possible to
> swap that out to disk?)

First time I've seen that. Very creative. But no, I've not done that.
cgroupfs has been fine with a fixed limit for a long time no so for now
it's fine to assume sockfs will be as well.