On Thu, Jun 09, 2016 at 08:21:05AM -0400, Jeff Layton wrote:
> Currently, the layout driver selection code always chooses the first one
> from the list. That's not really ideal however, as the server can send
> the list of layout types in any order that it likes. It's up to the
> client to select the best one for its needs.
>
> This patch adds an ordered list of preferred driver types and has the
> selection code sort the list of avaiable layout drivers according to it.
> Any unrecognized layout type is sorted to the end of the list.
>
> For now, the order of preference is hardcoded, but it should be possible
> to make this configurable in the future.
>
> Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
> ---
> fs/nfs/pnfs.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 50 insertions(+), 7 deletions(-)
>
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 2fc1b9354345..c31d30f1e5f2 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -99,6 +99,21 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
> }
>
> /*
> + * When the server sends a list of layout types, we choose one in the order
> + * given in the list below.
> + *
> + * FIXME: should this list be configurable via module_param or mount option?
> + */
> +static const u32 ld_prefs[] = {
> + LAYOUT_SCSI,
> + LAYOUT_BLOCK_VOLUME,
> + LAYOUT_OSD2_OBJECTS,
> + LAYOUT_FLEX_FILES,
> + LAYOUT_NFSV4_1_FILES,
> + 0
> +};
> +
> +/*
> * Try to set the server's pnfs module to the pnfs layout type specified by id.
> * Currently only one pNFS layout driver per filesystem is supported.
> *
> @@ -110,6 +125,8 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> {
> struct pnfs_layoutdriver_type *ld_type = NULL;
> u32 id;
> + int i, j;
> + bool swapped;
>
> if (!(server->nfs_client->cl_exchange_flags &
> (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
> @@ -118,18 +135,44 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> goto out_no_driver;
> }
>
> - id = ids[0];
> - if (!id)
> - goto out_no_driver;
> + /* bubble sort into ld_prefs order */
> + do {
> + swapped = false;
> + for (i = 0; i < (NFS_MAX_LAYOUT_TYPES - 1); i++) {
>
> - ld_type = find_pnfs_driver(id);
> - if (!ld_type) {
> - request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
> + /* If either is zero then we're done with this pass */
> + if (ids[i] == 0 || ids[i + 1] == 0)
> + break;
> +
> + for (j = 0; ld_prefs[j] != 0; j++) {
> + /* If we match left entry first, no swap */
> + if (ids[i] == ld_prefs[j])
> + break;
> +
> + /* if we match the right, we need to swap */
> + if (ids[i + 1] == ld_prefs[j]) {
> + swap(ids[i], ids[i + 1]);
> + swapped = true;
> + break;
> + }
> + }
> + }
> + } while (swapped);
Maybe I'm strange, but, yes, to me this is easier to read as on a first
pass I can just take your word that the above is doing a sort and see
much more quickly what's happening....
Anyway, ACK to the series from me.
--b.
> +
> + for (i = 0; i < NFS_MAX_LAYOUT_TYPES && ids[i] != 0; i++) {
> + id = ids[i];
> ld_type = find_pnfs_driver(id);
> + if (!ld_type) {
> + request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX,
> + id);
> + ld_type = find_pnfs_driver(id);
> + }
> + if (ld_type)
> + break;
> }
>
> if (!ld_type) {
> - dprintk("%s: No pNFS module found for %u.\n", __func__, id);
> + dprintk("%s: No pNFS module found!\n", __func__);
> goto out_no_driver;
> }
>
> --
> 2.5.5
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