Re: [PATCH v3 1/2] exportfs: clarify the documentation of open()/permission() expotrfs ops

["Chuck Lever" <cel@kernel.org>]

Typo in Subject: s/expotrfs/exportfs


On Wed, Jan 28, 2026, at 6:16 AM, Amir Goldstein wrote:
> pidfs and nsfs recently gained support for encode/decode of file handles
> via name_to_handle_at(2)/opan_by_handle_at(2).

s/opan/open

And one more below:


> These special kernel filesystems have custom ->open() and ->permission()
> export methods, which nfsd does not respect and it was never meant to be
> used for exporting those filesystems by nfsd.
>
> Update kernel-doc comments to express the fact the those methods are for
> open_by_handle(2) system only and not compatible with nfsd.
>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> ---
>  include/linux/exportfs.h | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index 262e24d833134..fafd22ed4c648 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -192,7 +192,9 @@ struct handle_to_path_ctx {
>  #define FILEID_VALID_USER_FLAGS	(FILEID_IS_CONNECTABLE | FILEID_IS_DIR)
> 
>  /**
> - * struct export_operations - for nfsd to communicate with file systems
> + * struct export_operations
> + *
> + * Methods for nfsd to communicate with file systems:

Let's not remove the brief description for the export_operations
struct in the Doxygen output.


>   * @encode_fh:      encode a file handle fragment from a dentry
>   * @fh_to_dentry:   find the implied object and get a dentry for it
>   * @fh_to_parent:   find the implied object's parent and get a dentry for it
> @@ -200,6 +202,10 @@ struct handle_to_path_ctx {
>   * @get_parent:     find the parent of a given directory
>   * @commit_metadata: commit metadata changes to stable storage
>   *
> + * Methods for open_by_handle(2) syscall with special kernel file systems:
> + * @permission:     custom permission for opening a file by handle
> + * @open:           custom open routine for opening file by handle
> + *
>   * See Documentation/filesystems/nfs/exporting.rst for details on how to use
>   * this interface correctly and the definition of the flags.
>   *
> @@ -244,10 +250,14 @@ struct handle_to_path_ctx {
>   *    space cannot be allocated, a %ERR_PTR should be returned.
>   *
>   * @permission:
> - *    Allow filesystems to specify a custom permission function.
> + *    Allow filesystems to specify a custom permission function for the
> + *    open_by_handle_at(2) syscall instead of the default permission check.
> + *    This custom permission function is not respected by nfsd.
>   *
>   * @open:
> - *    Allow filesystems to specify a custom open function.
> + *    Allow filesystems to specify a custom open function for the
> + *    open_by_handle_at(2) syscall instead of the default file_open_root().
> + *    This custom open function is not respected by nfsd.
>   *
>   * @commit_metadata:
>   *    @commit_metadata should commit metadata changes to stable storage.
> -- 
> 2.52.0

-- 
Chuck Lever