NFS: Minor read optimisation...

Since PG_uptodate may now end up getting set during the call to
nfs_wb_page(), we can avoid putting a read request on the wire in those
situations.

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

1 files changed, 23 insertions, 11 deletions

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 7bd7cb95c03..c07d0d10d9e 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -483,17 +483,19 @@ int nfs_readpage(struct file *file, struct page *page)
          */
         error = nfs_wb_page(inode, page);
         if (error)
-                goto out_error;
+                goto out_unlock;
+        if (PageUptodate(page))
+                goto out_unlock;
 
         error = -ESTALE;
         if (NFS_STALE(inode))
-                goto out_error;
+                goto out_unlock;
 
         if (file == NULL) {
                 error = -EBADF;
                 ctx = nfs_find_open_context(inode, NULL, FMODE_READ);
                 if (ctx == NULL)
-                        goto out_error;
+                        goto out_unlock;
         } else
                 ctx = get_nfs_open_context((struct nfs_open_context *)
                                 file->private_data);
@@ -502,8 +504,7 @@ int nfs_readpage(struct file *file, struct page *page)
 
         put_nfs_open_context(ctx);
         return error;
-
-out_error:
+out_unlock:
         unlock_page(page);
         return error;
 }
@@ -520,21 +521,32 @@ readpage_async_filler(void *data, struct page *page)
         struct inode *inode = page->mapping->host;
         struct nfs_page *new;
         unsigned int len;
+        int error;
+
+        error = nfs_wb_page(inode, page);
+        if (error)
+                goto out_unlock;
+        if (PageUptodate(page))
+                goto out_unlock;
 
-        nfs_wb_page(inode, page);
         len = nfs_page_length(page);
         if (len == 0)
                 return nfs_return_empty_page(page);
+
         new = nfs_create_request(desc->ctx, inode, page, 0, len);
-        if (IS_ERR(new)) {
-                        SetPageError(page);
-                        unlock_page(page);
-                        return PTR_ERR(new);
-        }
+        if (IS_ERR(new))
+                goto out_error;
+
         if (len < PAGE_CACHE_SIZE)
                 zero_user_page(page, len, PAGE_CACHE_SIZE - len, KM_USER0);
         nfs_pageio_add_request(desc->pgio, new);
         return 0;
+out_error:
+        error = PTR_ERR(new);
+        SetPageError(page);
+out_unlock:
+        unlock_page(page);
+        return error;
 }
 
 int nfs_readpages(struct file *filp, struct address_space *mapping,