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>

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 7bd7cb95c034d8bbcdbcdb05fbba5f46a291e68c..c07d0d10d9eddf5a915b71950e1ef24670fac7de 100644 (file)
--- 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,