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

["Darrick J. Wong" <djwong@kernel.org>]

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?

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

--D

>  
>  enum kernfs_node_flag {
>  	KERNFS_ACTIVATED	= 0x0010,
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index f60357d9f938..90a43a117127 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -118,6 +118,20 @@ struct simple_xattr {
>  	char value[];
>  };
>  
> +#define SIMPLE_XATTR_MAX_NR		128
> +#define SIMPLE_XATTR_MAX_SIZE		(128 << 10)
> +
> +struct simple_xattr_limits {
> +	atomic_t	nr_xattrs;	/* current user.* xattr count */
> +	atomic_t	xattr_size;	/* current total user.* value bytes */
> +};
> +
> +static inline void simple_xattr_limits_init(struct simple_xattr_limits *limits)
> +{
> +	atomic_set(&limits->nr_xattrs, 0);
> +	atomic_set(&limits->xattr_size, 0);
> +}
> +
>  int simple_xattrs_init(struct simple_xattrs *xattrs);
>  struct simple_xattrs *simple_xattrs_alloc(void);
>  struct simple_xattrs *simple_xattrs_lazy_alloc(struct simple_xattrs **xattrsp,
> @@ -132,6 +146,10 @@ int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
>  struct simple_xattr *simple_xattr_set(struct simple_xattrs *xattrs,
>  				      const char *name, const void *value,
>  				      size_t size, int flags);
> +int simple_xattr_set_limited(struct simple_xattrs *xattrs,
> +			     struct simple_xattr_limits *limits,
> +			     const char *name, const void *value,
> +			     size_t size, int flags);
>  ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
>  			  char *buffer, size_t size);
>  int simple_xattr_add(struct simple_xattrs *xattrs,
> 
> -- 
> 2.47.3
> 
>