On Mon, 2016-06-13 at 16:05 -0400, J. Bruce Fields wrote: > 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.... > Yeah, it is for me too, actually. Good call on asking for it. ;) That said, I did notice the code in lib/sort.c after I sent this series. It might be better to use that instead of this hand-rolled bubble sort (if only for conciseness -- I doubt it matters for efficiency). > Anyway, ACK to the series from me. > Thanks! > --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 -- Jeff Layton <jlayton@xxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html