Re: [PATCH 13/14] xattr: add a function to check if a namespace is supported

[Chuck Lever <chuck.lever@oracle.com>]

> On Mar 11, 2020, at 3:59 PM, Frank van der Linden <fllinden@amazon.com> wrote:
> 
> Add a function that checks is an extended attribute namespace is
> supported for an inode.
> 
> To be used by the nfs server code when being queried for extended
> attributes support.

Here's a patch that needs to be cc: linux-fsdevel.

Also, perhaps 13/14 and 14/14 could be squashed together.


> Signed-off-by: Frank van der Linden <fllinden@amazon.com>
> ---
> fs/xattr.c            | 27 +++++++++++++++++++++++++++
> include/linux/xattr.h |  2 ++
> 2 files changed, 29 insertions(+)
> 
> diff --git a/fs/xattr.c b/fs/xattr.c
> index 58013bcbc333..7d0ebab1df30 100644
> --- a/fs/xattr.c
> +++ b/fs/xattr.c
> @@ -134,6 +134,33 @@ xattr_permission(struct inode *inode, const char *name, int mask)
> 	return inode_permission(inode, mask);
> }
> 
> +/*
> + * Look for any handler that deals with the specified namespace.
> + */
> +int
> +xattr_supported_namespace(struct inode *inode, const char *prefix)
> +{
> +	const struct xattr_handler **handlers = inode->i_sb->s_xattr;
> +	const struct xattr_handler *handler;
> +	size_t preflen;
> +
> +	if (!(inode->i_opflags & IOP_XATTR)) {
> +		if (unlikely(is_bad_inode(inode)))
> +			return -EIO;
> +		return -EOPNOTSUPP;
> +	}
> +
> +	preflen = strlen(prefix);
> +
> +	for_each_xattr_handler(handlers, handler) {
> +		if (!strncmp(xattr_prefix(handler), prefix, preflen))
> +			return 0;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +EXPORT_SYMBOL(xattr_supported_namespace);
> +
> int
> __vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
> 	       const void *value, size_t size, int flags)
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index 3a71ad716da5..32e377602068 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -61,6 +61,8 @@ ssize_t generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_siz
> ssize_t vfs_getxattr_alloc(struct dentry *dentry, const char *name,
> 			   char **xattr_value, size_t size, gfp_t flags);
> 
> +int xattr_supported_namespace(struct inode *inode, const char *prefix);
> +
> static inline const char *xattr_prefix(const struct xattr_handler *handler)
> {
> 	return handler->prefix ?: handler->name;
> -- 
> 2.16.6
> 

--
Chuck Lever