pnfs: allow splicing pre-encoded pages into the layoutcommit args

Currently there is no XDR buffer space allocated for the per-layout driver
layoutcommit payload, which leads to server buffer overflows in the
blocklayout driver even under simple workloads.  As we can't do per-layout
sizes for XDR operations we'll have to splice a previously encoded list
of pages into the XDR stream, similar to how we handle ACL buffers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 13 insertions, 5 deletions

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index e13b59d8d9aa..f2cd957adb90 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -395,7 +395,10 @@ static int nfs4_stat_to_errno(int);
                                 2 /* last byte written */ + \
                                 1 /* nt_timechanged (false) */ + \
                                 1 /* layoutupdate4 layout type */ + \
-                                1 /* NULL filelayout layoutupdate4 payload */)
+                                1 /* layoutupdate4 opaqueue len */)
+                                  /* the actual content of layoutupdate4 should
+                                     be allocated by drivers and spliced in
+                                     using xdr_write_pages */
 #define decode_layoutcommit_maxsz (op_decode_hdr_maxsz + 3)
 #define encode_layoutreturn_maxsz (8 + op_encode_hdr_maxsz + \
                                 encode_stateid_maxsz + \
@@ -1990,7 +1993,7 @@ encode_layoutget(struct xdr_stream *xdr,
 static int
 encode_layoutcommit(struct xdr_stream *xdr,
                     struct inode *inode,
-                    const struct nfs4_layoutcommit_args *args,
+                    struct nfs4_layoutcommit_args *args,
                     struct compound_hdr *hdr)
 {
         __be32 *p;
@@ -2011,11 +2014,16 @@ encode_layoutcommit(struct xdr_stream *xdr,
         *p++ = cpu_to_be32(0); /* Never send time_modify_changed */
         *p++ = cpu_to_be32(NFS_SERVER(args->inode)->pnfs_curr_ld->id);/* type */
 
-        if (NFS_SERVER(inode)->pnfs_curr_ld->encode_layoutcommit)
+        if (NFS_SERVER(inode)->pnfs_curr_ld->encode_layoutcommit) {
                 NFS_SERVER(inode)->pnfs_curr_ld->encode_layoutcommit(
                         NFS_I(inode)->layout, xdr, args);
-        else
-                encode_uint32(xdr, 0); /* no layout-type payload */
+        } else {
+                encode_uint32(xdr, args->layoutupdate_len);
+                if (args->layoutupdate_pages) {
+                        xdr_write_pages(xdr, args->layoutupdate_pages, 0,
+                                        args->layoutupdate_len);
+                }
+        }
 
         return 0;
 }