linux-ext4 - Re: [PATCH RFC 02/15] fanotify: Split fsid check from other fid mode checks

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Date:   Tue, 27 Apr 2021 07:53:06 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     Theodore Tso <tytso@....edu>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
        David Howells <dhowells@...hat.com>,
        Khazhismel Kumykov <khazhy@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>, kernel@...labora.com
Subject: Re: [PATCH RFC 02/15] fanotify: Split fsid check from other fid mode checks

On Mon, Apr 26, 2021 at 9:42 PM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> FAN_ERROR will require fsid, but not necessarily require the filesystem
> to expose a file handle.  Split those checks into different functions, so
> they can be used separately when creating a mark.

Ok for the split, but...

>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
>  fs/notify/fanotify/fanotify_user.c | 35 +++++++++++++++++++-----------
>  1 file changed, 22 insertions(+), 13 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 0332c4afeec3..e0d113e3b65c 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1055,7 +1055,23 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
>  }
>
>  /* Check if filesystem can encode a unique fid */
> -static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
> +static int fanotify_test_fid(struct path *path)

This helper can take a dentry.

> +{
> +       /*
> +        * We need to make sure that the file system supports at least
> +        * encoding a file handle so user can use name_to_handle_at() to
> +        * compare fid returned with event to the file handle of watched
> +        * objects. However, name_to_handle_at() requires that the
> +        * filesystem also supports decoding file handles.
> +        */
> +       if (!path->dentry->d_sb->s_export_op ||
> +           !path->dentry->d_sb->s_export_op->fh_to_dentry)
> +               return -EOPNOTSUPP;
> +
> +       return 0;
> +}
> +
> +static int fanotify_check_path_fsid(struct path *path, __kernel_fsid_t *fsid)

And so does this helper.
I certainly don't see the need for the _path_ in the helper name.

>  {
>         __kernel_fsid_t root_fsid;
>         int err;
> @@ -1082,17 +1098,6 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
>             root_fsid.val[1] != fsid->val[1])
>                 return -EXDEV;
>
> -       /*
> -        * We need to make sure that the file system supports at least
> -        * encoding a file handle so user can use name_to_handle_at() to
> -        * compare fid returned with event to the file handle of watched
> -        * objects. However, name_to_handle_at() requires that the
> -        * filesystem also supports decoding file handles.
> -        */
> -       if (!path->dentry->d_sb->s_export_op ||
> -           !path->dentry->d_sb->s_export_op->fh_to_dentry)
> -               return -EOPNOTSUPP;
> -
>         return 0;
>  }
>
> @@ -1230,7 +1235,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
>         }
>
>         if (fid_mode) {
> -               ret = fanotify_test_fid(&path, &__fsid);
> +               ret = fanotify_check_path_fsid(&path, &__fsid);
> +               if (ret)
> +                       goto path_put_and_out;
> +
> +               ret = fanotify_test_fid(&path);

Whether _test_ or _check_ please stick to one.

Thanks,
Amir.