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, 22 insertions, 7 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 80bc4ea1b824..1ce0c200df16 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -89,18 +89,33 @@ static mempool_t *nfs_commit_mempool;
 
 static DECLARE_WAIT_QUEUE_HEAD(nfs_write_congestion);
 
-static inline struct nfs_write_data *nfs_commit_alloc(void)
+static inline struct nfs_write_data *nfs_commit_alloc(unsigned int pagecount)
 {
         struct nfs_write_data *p = mempool_alloc(nfs_commit_mempool, SLAB_NOFS);
+
         if (p) {
                 memset(p, 0, sizeof(*p));
                 INIT_LIST_HEAD(&p->pages);
+                if (pagecount < NFS_PAGEVEC_SIZE)
+                        p->pagevec = &p->page_array[0];
+                else {
+                        size_t size = ++pagecount * sizeof(struct page *);
+                        p->pagevec = kmalloc(size, GFP_NOFS);
+                        if (p->pagevec) {
+                                memset(p->pagevec, 0, size);
+                        } else {
+                                mempool_free(p, nfs_commit_mempool);
+                                p = NULL;
+                        }
+                }
         }
         return p;
 }
 
 static inline void nfs_commit_free(struct nfs_write_data *p)
 {
+        if (p && (p->pagevec != &p->page_array[0]))
+                kfree(p->pagevec);
         mempool_free(p, nfs_commit_mempool);
 }
 
@@ -167,7 +182,7 @@ static int nfs_writepage_sync(struct nfs_open_context *ctx, struct inode *inode,
         int             result, written = 0;
         struct nfs_write_data *wdata;
 
-        wdata = nfs_writedata_alloc();
+        wdata = nfs_writedata_alloc(1);
         if (!wdata)
                 return -ENOMEM;
 
@@ -909,7 +924,7 @@ static int nfs_flush_multi(struct list_head *head, struct inode *inode, int how)
 
         nbytes = req->wb_bytes;
         for (;;) {
-                data = nfs_writedata_alloc();
+                data = nfs_writedata_alloc(1);
                 if (!data)
                         goto out_bad;
                 list_add(&data->pages, &list);
@@ -973,7 +988,7 @@ static int nfs_flush_one(struct list_head *head, struct inode *inode, int how)
         if (NFS_SERVER(inode)->wsize < PAGE_CACHE_SIZE)
                 return nfs_flush_multi(head, inode, how);
 
-        data = nfs_writedata_alloc();
+        data = nfs_writedata_alloc(NFS_SERVER(inode)->wpages);
         if (!data)
                 goto out_bad;
 
@@ -1241,12 +1256,12 @@ static void nfs_commit_rpcsetup(struct list_head *head,
  * Commit dirty pages
  */
 static int
-nfs_commit_list(struct list_head *head, int how)
+nfs_commit_list(struct inode *inode, struct list_head *head, int how)
 {
         struct nfs_write_data   *data;
         struct nfs_page         *req;
 
-        data = nfs_commit_alloc();
+        data = nfs_commit_alloc(NFS_SERVER(inode)->wpages);
 
         if (!data)
                 goto out_bad;
@@ -1351,7 +1366,7 @@ int nfs_commit_inode(struct inode *inode, int how)
         res = nfs_scan_commit(inode, &head, 0, 0);
         spin_unlock(&nfsi->req_lock);
         if (res) {
-                error = nfs_commit_list(&head, how);
+                error = nfs_commit_list(inode, &head, how);
                 if (error < 0)
                         return error;
         }