Re: [RFC PATCH] ceph: guard against __ceph_remove_cap races

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2020-11-11 at 14:11 +0000, Luis Henriques wrote:
> 
> 

It think this looks reasonable. Minor nits below:

> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> index ded4229c314a..917dfaf0bd01 100644
> --- a/fs/ceph/caps.c
> +++ b/fs/ceph/caps.c
> @@ -1140,12 +1140,17 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release)
>  {
>         struct ceph_mds_session *session = cap->session;
>         struct ceph_inode_info *ci = cap->ci;
> -       struct ceph_mds_client *mdsc =
> -               ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
> +       struct ceph_mds_client *mdsc;
> +

nit: remove the above newline

>         int removed = 0;
>  

Maybe add a comment here to the effect that a NULL cap->ci indicates
that the remove has already been done?

> +       if (!ci)
> +               return;
> +
>         dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode);
>  
> +       mdsc = ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc;
> +

There's a ceph_inode_to_client helper now that may make this a bit more
readable.

>         /* remove from inode's cap rbtree, and clear auth cap */
>         rb_erase(&cap->ci_node, &ci->i_caps);
>         if (ci->i_auth_cap == cap) {

-- 
Jeff Layton <jlayton@kernel.org>