NFS: Optimize allocation of nfs_read/write_data structures

Clean up use of page_array, and fix an off-by-one error noticed by Tom
Talpey which causes kmalloc calls in cases where using the page_array
is sufficient.

Test plan:
Normal client functional testing with r/wsize=32768.

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

3 files changed, 13 insertions, 20 deletions

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 4b5f58da5650..fd9018c692bb 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -51,14 +51,11 @@ struct nfs_read_data *nfs_readdata_alloc(unsigned int pagecount)
         if (p) {
                 memset(p, 0, sizeof(*p));
                 INIT_LIST_HEAD(&p->pages);
-                if (pagecount < NFS_PAGEVEC_SIZE)
-                        p->pagevec = &p->page_array[0];
+                if (pagecount <= ARRAY_SIZE(p->page_array))
+                        p->pagevec = p->page_array;
                 else {
-                        size_t size = ++pagecount * sizeof(struct page *);
-                        p->pagevec = kmalloc(size, GFP_NOFS);
-                        if (p->pagevec) {
-                                memset(p->pagevec, 0, size);
-                        } else {
+                        p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_NOFS);
+                        if (!p->pagevec) {
                                 mempool_free(p, nfs_rdata_mempool);
                                 p = NULL;
                         }
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 4cfada2cc09f..a515ec714bb6 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -98,11 +98,10 @@ struct nfs_write_data *nfs_commit_alloc(unsigned int pagecount)
         if (p) {
                 memset(p, 0, sizeof(*p));
                 INIT_LIST_HEAD(&p->pages);
-                if (pagecount < NFS_PAGEVEC_SIZE)
-                        p->pagevec = &p->page_array[0];
+                if (pagecount <= ARRAY_SIZE(p->page_array))
+                        p->pagevec = p->page_array;
                 else {
-                        size_t size = ++pagecount * sizeof(struct page *);
-                        p->pagevec = kzalloc(size, GFP_NOFS);
+                        p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_NOFS);
                         if (!p->pagevec) {
                                 mempool_free(p, nfs_commit_mempool);
                                 p = NULL;
@@ -126,14 +125,11 @@ struct nfs_write_data *nfs_writedata_alloc(unsigned int pagecount)
         if (p) {
                 memset(p, 0, sizeof(*p));
                 INIT_LIST_HEAD(&p->pages);
-                if (pagecount < NFS_PAGEVEC_SIZE)
-                        p->pagevec = &p->page_array[0];
+                if (pagecount <= ARRAY_SIZE(p->page_array))
+                        p->pagevec = p->page_array;
                 else {
-                        size_t size = ++pagecount * sizeof(struct page *);
-                        p->pagevec = kmalloc(size, GFP_NOFS);
-                        if (p->pagevec) {
-                                memset(p->pagevec, 0, size);
-                        } else {
+                        p->pagevec = kcalloc(pagecount, sizeof(struct page *), GFP_NOFS);
+                        if (!p->pagevec) {
                                 mempool_free(p, nfs_wdata_mempool);
                                 p = NULL;
                         }
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index c483e239f993..e206c07080fe 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -694,7 +694,7 @@ struct nfs_read_data {
 #ifdef CONFIG_NFS_V4
         unsigned long           timestamp;      /* For lease renewal */
 #endif
-        struct page             *page_array[NFS_PAGEVEC_SIZE + 1];
+        struct page             *page_array[NFS_PAGEVEC_SIZE];
 };
 
 struct nfs_write_data {
@@ -712,7 +712,7 @@ struct nfs_write_data {
 #ifdef CONFIG_NFS_V4
         unsigned long           timestamp;      /* For lease renewal */
 #endif
-        struct page             *page_array[NFS_PAGEVEC_SIZE + 1];
+        struct page             *page_array[NFS_PAGEVEC_SIZE];
 };
 
 struct nfs_access_entry;