Re: [RFC PATCH 08/53] netfs: Add rsize to netfs_io_request

[Jeff Layton]

On Fri, 2023-10-13 at 17:03 +0100, David Howells wrote:
> Add an rsize parameter to netfs_io_request to be filled in by the network
> filesystem when the request is initialised.  This indicates the maximum
> size of a read request that the netfs will honour in that region.
> 
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Jeff Layton <jlayton@xxxxxxxxxx>
> cc: linux-cachefs@xxxxxxxxxx
> cc: linux-fsdevel@xxxxxxxxxxxxxxx
> cc: linux-mm@xxxxxxxxx
> ---
>  fs/afs/file.c         | 1 +
>  fs/ceph/addr.c        | 2 ++
>  include/linux/netfs.h | 1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/fs/afs/file.c b/fs/afs/file.c
> index 3fea5cd8ef13..3d2e1913ea27 100644
> --- a/fs/afs/file.c
> +++ b/fs/afs/file.c
> @@ -360,6 +360,7 @@ static int afs_symlink_read_folio(struct file *file, struct folio *folio)
>  static int afs_init_request(struct netfs_io_request *rreq, struct file *file)
>  {
>  	rreq->netfs_priv = key_get(afs_file_key(file));
> +	rreq->rsize = 4 * 1024 * 1024;
>  	return 0;
>  }
>  
> diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
> index ced19ff08988..92a5ddcd9a76 100644
> --- a/fs/ceph/addr.c
> +++ b/fs/ceph/addr.c
> @@ -419,6 +419,8 @@ static int ceph_init_request(struct netfs_io_request *rreq, struct file *file)
>  	struct ceph_netfs_request_data *priv;
>  	int ret = 0;
>  
> +	rreq->rsize = 1024 * 1024;
> +

Holy magic numbers, batman! I think this deserves a comment that
explains how you came up with these values.

Also, do 9p and cifs not need this for some reason?

>  	if (rreq->origin != NETFS_READAHEAD)
>  		return 0;
>  
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index daa431c4148d..02e888c170da 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -188,6 +188,7 @@ struct netfs_io_request {
>  	struct list_head	subrequests;	/* Contributory I/O operations */
>  	void			*netfs_priv;	/* Private data for the netfs */
>  	unsigned int		debug_id;
> +	unsigned int		rsize;		/* Maximum read size (0 for none) */
>  	atomic_t		nr_outstanding;	/* Number of ops in progress */
>  	atomic_t		nr_copy_ops;	/* Number of copy-to-cache ops in progress */
>  	size_t			submitted;	/* Amount submitted for I/O so far */
> 

-- 
Jeff Layton <jlayton@xxxxxxxxxx>