nfs: don't create zero-length requests

commit 149a4fddd0a72d526abbeac0c8deaab03559836a upstream.

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>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index ecb0f9fd56326766ce9b54971cfcdc3c9114d019..34f18294817aa09d0de0d090589863620e424bf1 100644 (file)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1222,6 +1222,9 @@ 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;
@@ -1232,7 +1235,7 @@ 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;