NFS: readdir with vmapped pages

We can use vmapped pages to read more information from the network at once.
This will reduce the number of calls needed to complete a readdir.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
[trondmy: Added #include for linux/vmalloc.h> in fs/nfs/dir.c]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 54 insertions, 12 deletions

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 88cbcda76856..5d7da3ad4e85 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -33,6 +33,7 @@
 #include <linux/namei.h>
 #include <linux/mount.h>
 #include <linux/sched.h>
+#include <linux/vmalloc.h>
 
 #include "delegation.h"
 #include "iostat.h"
@@ -327,7 +328,7 @@ out:
 
 /* Fill a page with xdr information before transferring to the cache page */
 static
-int nfs_readdir_xdr_filler(struct page *xdr_page, nfs_readdir_descriptor_t *desc,
+int nfs_readdir_xdr_filler(struct page **pages, nfs_readdir_descriptor_t *desc,
                         struct nfs_entry *entry, struct file *file, struct inode *inode)
 {
         struct rpc_cred *cred = nfs_file_cred(file);
@@ -337,7 +338,7 @@ int nfs_readdir_xdr_filler(struct page *xdr_page, nfs_readdir_descriptor_t *desc
  again:
         timestamp = jiffies;
         gencount = nfs_inc_attr_generation_counter();
-        error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, xdr_page,
+        error = NFS_PROTO(inode)->readdir(file->f_path.dentry, cred, entry->cookie, pages,
                                           NFS_SERVER(inode)->dtsize, desc->plus);
         if (error < 0) {
                 /* We requested READDIRPLUS, but the server doesn't grok it */
@@ -436,11 +437,11 @@ out:
 /* Perform conversion from xdr to cache array */
 static
 void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *entry,
-                                struct page *xdr_page, struct page *page, unsigned int buflen)
+                                void *xdr_page, struct page *page, unsigned int buflen)
 {
         struct xdr_stream stream;
         struct xdr_buf buf;
-        __be32 *ptr = kmap(xdr_page);
+        __be32 *ptr = xdr_page;
 
         buf.head->iov_base = xdr_page;
         buf.head->iov_len = buflen;
@@ -458,18 +459,59 @@ void nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *e
                 if (desc->plus == 1)
                         nfs_prime_dcache(desc->file->f_path.dentry, entry);
         }
-        kunmap(xdr_page);
+}
+
+static
+void nfs_readdir_free_pagearray(struct page **pages, unsigned int npages)
+{
+        unsigned int i;
+        for (i = 0; i < npages; i++)
+                put_page(pages[i]);
+}
+
+static
+void nfs_readdir_free_large_page(void *ptr, struct page **pages,
+                unsigned int npages)
+{
+        vm_unmap_ram(ptr, npages);
+        nfs_readdir_free_pagearray(pages, npages);
+}
+
+/*
+ * nfs_readdir_large_page will allocate pages that must be freed with a call
+ * to nfs_readdir_free_large_page
+ */
+static
+void *nfs_readdir_large_page(struct page **pages, unsigned int npages)
+{
+        void *ptr;
+        unsigned int i;
+
+        for (i = 0; i < npages; i++) {
+                struct page *page = alloc_page(GFP_KERNEL);
+                if (page == NULL)
+                        goto out_freepages;
+                pages[i] = page;
+        }
+
+        ptr = vm_map_ram(pages, NFS_MAX_READDIR_PAGES, 0, PAGE_KERNEL);
+        if (!IS_ERR_OR_NULL(ptr))
+                return ptr;
+out_freepages:
+        nfs_readdir_free_pagearray(pages, i);
+        return NULL;
 }
 
 static
 int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page, struct inode *inode)
 {
-        struct page *xdr_page;
+        struct page *pages[NFS_MAX_READDIR_PAGES];
+        void *pages_ptr = NULL;
         struct nfs_entry entry;
         struct file     *file = desc->file;
         struct nfs_cache_array *array;
         int status = 0;
-        unsigned int array_size = 1;
+        unsigned int array_size = ARRAY_SIZE(pages);
 
         entry.prev_cookie = 0;
         entry.cookie = *desc->dir_cookie;
@@ -483,18 +525,18 @@ int nfs_readdir_xdr_to_array(nfs_readdir_descriptor_t *desc, struct page *page,
         memset(array, 0, sizeof(struct nfs_cache_array));
         array->eof_index = -1;
 
-        xdr_page = alloc_page(GFP_KERNEL);
-        if (!xdr_page)
+        pages_ptr = nfs_readdir_large_page(pages, array_size);
+        if (!pages_ptr)
                 goto out_release_array;
         do {
-                status = nfs_readdir_xdr_filler(xdr_page, desc, &entry, file, inode);
+                status = nfs_readdir_xdr_filler(pages, desc, &entry, file, inode);
 
                 if (status < 0)
                         break;
-                nfs_readdir_page_filler(desc, &entry, xdr_page, page, array_size * PAGE_SIZE);
+                nfs_readdir_page_filler(desc, &entry, pages_ptr, page, array_size * PAGE_SIZE);
         } while (array->eof_index < 0 && array->size < MAX_READDIR_ARRAY);
 
-        put_page(xdr_page);
+        nfs_readdir_free_large_page(pages_ptr, pages, array_size);
 out_release_array:
         nfs_readdir_release_array(page);
 out: