pnfs: add a new mechanism to select a layout driver according to an ordered list

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 available 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 <jlayton@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@fieldses.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 18 insertions, 13 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 41a02f994976..17b4e059c588 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4728,29 +4728,34 @@ static int decode_getfattr(struct xdr_stream *xdr, struct nfs_fattr *fattr,
  * Decode potentially multiple layout types.
  */
 static int decode_pnfs_layout_types(struct xdr_stream *xdr,
-                                         uint32_t *layouttype)
+                                    struct nfs_fsinfo *fsinfo)
 {
         __be32 *p;
-        uint32_t num, i;
+        uint32_t i;
 
         p = xdr_inline_decode(xdr, 4);
         if (unlikely(!p))
                 goto out_overflow;
-        num = be32_to_cpup(p);
+        fsinfo->nlayouttypes = be32_to_cpup(p);
 
         /* pNFS is not supported by the underlying file system */
-        if (num == 0) {
+        if (fsinfo->nlayouttypes == 0)
                 return 0;
-        }
-        if (num > NFS_MAX_LAYOUT_TYPES)
-                printk(KERN_INFO "NFS: %s: Warning: Too many (%d) pNFS layout types\n", __func__, num);
 
         /* Decode and set first layout type, move xdr->p past unused types */
-        p = xdr_inline_decode(xdr, num * 4);
+        p = xdr_inline_decode(xdr, fsinfo->nlayouttypes * 4);
         if (unlikely(!p))
                 goto out_overflow;
-        for(i = 0; i < num && i < NFS_MAX_LAYOUT_TYPES; i++)
-                layouttype[i] = be32_to_cpup(p++);
+
+        /* If we get too many, then just cap it at the max */
+        if (fsinfo->nlayouttypes > NFS_MAX_LAYOUT_TYPES) {
+                printk(KERN_INFO "NFS: %s: Warning: Too many (%u) pNFS layout types\n",
+                        __func__, fsinfo->nlayouttypes);
+                fsinfo->nlayouttypes = NFS_MAX_LAYOUT_TYPES;
+        }
+
+        for(i = 0; i < fsinfo->nlayouttypes; ++i)
+                fsinfo->layouttype[i] = be32_to_cpup(p++);
         return 0;
 out_overflow:
         print_overflow_msg(__func__, xdr);
@@ -4762,7 +4767,7 @@ out_overflow:
  * Note we must ensure that layouttype is set in any non-error case.
  */
 static int decode_attr_pnfstype(struct xdr_stream *xdr, uint32_t *bitmap,
-                                uint32_t *layouttype)
+                                struct nfs_fsinfo *fsinfo)
 {
         int status = 0;
 
@@ -4770,7 +4775,7 @@ static int decode_attr_pnfstype(struct xdr_stream *xdr, uint32_t *bitmap,
         if (unlikely(bitmap[1] & (FATTR4_WORD1_FS_LAYOUT_TYPES - 1U)))
                 return -EIO;
         if (bitmap[1] & FATTR4_WORD1_FS_LAYOUT_TYPES) {
-                status = decode_pnfs_layout_types(xdr, layouttype);
+                status = decode_pnfs_layout_types(xdr, fsinfo);
                 bitmap[1] &= ~FATTR4_WORD1_FS_LAYOUT_TYPES;
         }
         return status;
@@ -4853,7 +4858,7 @@ static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
         status = decode_attr_time_delta(xdr, bitmap, &fsinfo->time_delta);
         if (status != 0)
                 goto xdr_error;
-        status = decode_attr_pnfstype(xdr, bitmap, fsinfo->layouttype);
+        status = decode_attr_pnfstype(xdr, bitmap, fsinfo);
         if (status != 0)
                 goto xdr_error;