SUNRPC: Add a label for RPC calls that require allocation on receive

If the RPC call relies on the receive call allocating pages as buffers,
then let's label it so that we
a) Don't leak memory by allocating pages for requests that do not expect
   this behaviour
b) Can optimise for the common case where calls do not require allocation.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

4 files changed, 6 insertions, 2 deletions

diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index 64e4fa33d89f..d8c4c10b15f7 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -1364,10 +1364,12 @@ static void nfs3_xdr_enc_getacl3args(struct rpc_rqst *req,
 
         encode_nfs_fh3(xdr, args->fh);
         encode_uint32(xdr, args->mask);
-        if (args->mask & (NFS_ACL | NFS_DFACL))
+        if (args->mask & (NFS_ACL | NFS_DFACL)) {
                 prepare_reply_buffer(req, args->pages, 0,
                                         NFSACL_MAXPAGES << PAGE_SHIFT,
                                         ACL3_getaclres_sz);
+                req->rq_rcv_buf.flags |= XDRBUF_SPARSE_PAGES;
+        }
 }
 
 static void nfs3_xdr_enc_setacl3args(struct rpc_rqst *req,
diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h
index 2bd68177a442..431829233392 100644
--- a/include/linux/sunrpc/xdr.h
+++ b/include/linux/sunrpc/xdr.h
@@ -58,6 +58,7 @@ struct xdr_buf {
                         flags;          /* Flags for data disposition */
 #define XDRBUF_READ             0x01            /* target of file read */
 #define XDRBUF_WRITE            0x02            /* source of file write */
+#define XDRBUF_SPARSE_PAGES     0x04            /* Page array is sparse */
 
         unsigned int    buflen,         /* Total length of storage buffer */
                         len;            /* Length of XDR encoded message */
diff --git a/net/sunrpc/auth_gss/gss_rpc_xdr.c b/net/sunrpc/auth_gss/gss_rpc_xdr.c
index 444380f968f1..006062ad5f58 100644
--- a/net/sunrpc/auth_gss/gss_rpc_xdr.c
+++ b/net/sunrpc/auth_gss/gss_rpc_xdr.c
@@ -784,6 +784,7 @@ void gssx_enc_accept_sec_context(struct rpc_rqst *req,
         xdr_inline_pages(&req->rq_rcv_buf,
                 PAGE_SIZE/2 /* pretty arbitrary */,
                 arg->pages, 0 /* page base */, arg->npages * PAGE_SIZE);
+        req->rq_rcv_buf.flags |= XDRBUF_SPARSE_PAGES;
 done:
         if (err)
                 dprintk("RPC:       gssx_enc_accept_sec_context: %d\n", err);
diff --git a/net/sunrpc/socklib.c b/net/sunrpc/socklib.c
index f217c348b341..08f00a98151f 100644
--- a/net/sunrpc/socklib.c
+++ b/net/sunrpc/socklib.c
@@ -104,7 +104,7 @@ ssize_t xdr_partial_copy_from_skb(struct xdr_buf *xdr, unsigned int base, struct
 
                 /* ACL likes to be lazy in allocating pages - ACLs
                  * are small by default but can get huge. */
-                if (unlikely(*ppage == NULL)) {
+                if ((xdr->flags & XDRBUF_SPARSE_PAGES) && *ppage == NULL) {
                         *ppage = alloc_page(GFP_ATOMIC);
                         if (unlikely(*ppage == NULL)) {
                                 if (copied == 0)