nfs: don't create zero-length requests

[ Upstream commit 149a4fddd0a72d526abbeac0c8deaab03559836a ]

NFS doesn't expect requests with wb_bytes set to zero and may make
unexpected decisions about how to handle that request at the page IO layer.
Skip request creation if we won't have any wb_bytes in the request.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Weston Andros Adamson <dros@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 6067f2a0b493a96398f88f15ddc7e99bbab86a43..395b93f43df5d597774a73c1590ec5118c457368 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1204,6 +1204,9 @@ int nfs_updatepage(struct file *file, struct page *page,
        dprintk("NFS:       nfs_updatepage(%pD2 %d@%lld)\n",
                file, count, (long long)(page_file_offset(page) + offset));
 
+       if (!count)
+               goto out;
+
        if (nfs_can_extend_write(file, page, inode)) {
                count = max(count + offset, nfs_page_length(page));
                offset = 0;
@@ -1214,7 +1217,7 @@ int nfs_updatepage(struct file *file, struct page *page,
                nfs_set_pageerror(page);
        else
                __set_page_dirty_nobuffers(page);
-
+out:
        dprintk("NFS:       nfs_updatepage returns %d (isize %lld)\n",
                        status, (long long)i_size_read(inode));
        return status;