NFS: support large reads and writes on the wire

 Most NFS server implementations allow up to 64KB reads and writes on the
 wire.  The Solaris NFS server allows up to a megabyte, for instance.

 Now the Linux NFS client supports transfer sizes up to 1MB, too.  This will
 help reduce protocol and context switch overhead on read/write intensive NFS
 workloads, and support larger atomic read and write operations on servers
 that support them.

 Test-plan:
 Connectathon and iozone on mount point with wsize=rsize>32768 over TCP.
 Tests with NFS over UDP to verify the maximum RPC payload size cap.

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 16 insertions, 13 deletions

diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index b8b0eed98ec9..9f422fd87673 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -4,6 +4,16 @@
 #include <linux/sunrpc/xprt.h>
 #include <linux/nfsacl.h>
 
+/*
+ * To change the maximum rsize and wsize supported by the NFS client, adjust
+ * NFS_MAX_FILE_IO_SIZE.  64KB is a typical maximum, but some servers can
+ * support a megabyte or more.  The default is left at 4096 bytes, which is
+ * reasonable for NFS over UDP.
+ */
+#define NFS_MAX_FILE_IO_SIZE    (1048576U)
+#define NFS_DEF_FILE_IO_SIZE    (4096U)
+#define NFS_MIN_FILE_IO_SIZE    (1024U)
+
 struct nfs4_fsid {
         __u64 major;
         __u64 minor;
@@ -215,12 +225,6 @@ struct nfs4_delegreturnargs {
 /*
  * Arguments to the read call.
  */
-
-#define NFS_READ_MAXIOV         (9U)
-#if (NFS_READ_MAXIOV > (MAX_IOVEC -2))
-#error "NFS_READ_MAXIOV is too large"
-#endif
-
 struct nfs_readargs {
         struct nfs_fh *         fh;
         struct nfs_open_context *context;
@@ -239,11 +243,6 @@ struct nfs_readres {
 /*
  * Arguments to the write call.
  */
-#define NFS_WRITE_MAXIOV        (9U)
-#if (NFS_WRITE_MAXIOV > (MAX_IOVEC -2))
-#error "NFS_WRITE_MAXIOV is too large"
-#endif
-
 struct nfs_writeargs {
         struct nfs_fh *         fh;
         struct nfs_open_context *context;
@@ -674,6 +673,8 @@ struct nfs4_server_caps_res {
 
 struct nfs_page;
 
+#define NFS_PAGEVEC_SIZE        (8U)
+
 struct nfs_read_data {
         int                     flags;
         struct rpc_task         task;
@@ -682,13 +683,14 @@ struct nfs_read_data {
         struct nfs_fattr        fattr;  /* fattr storage */
         struct list_head        pages;  /* Coalesced read requests */
         struct nfs_page         *req;   /* multi ops per nfs_page */
-        struct page             *pagevec[NFS_READ_MAXIOV];
+        struct page             **pagevec;
         struct nfs_readargs args;
         struct nfs_readres  res;
 #ifdef CONFIG_NFS_V4
         unsigned long           timestamp;      /* For lease renewal */
 #endif
         void (*complete) (struct nfs_read_data *, int);
+        struct page             *page_array[NFS_PAGEVEC_SIZE + 1];
 };
 
 struct nfs_write_data {
@@ -700,13 +702,14 @@ struct nfs_write_data {
         struct nfs_writeverf    verf;
         struct list_head        pages;          /* Coalesced requests we wish to flush */
         struct nfs_page         *req;           /* multi ops per nfs_page */
-        struct page             *pagevec[NFS_WRITE_MAXIOV];
+        struct page             **pagevec;
         struct nfs_writeargs    args;           /* argument struct */
         struct nfs_writeres     res;            /* result struct */
 #ifdef CONFIG_NFS_V4
         unsigned long           timestamp;      /* For lease renewal */
 #endif
         void (*complete) (struct nfs_write_data *, int);
+        struct page             *page_array[NFS_PAGEVEC_SIZE + 1];
 };
 
 struct nfs_access_entry;