linux-kernel - [PATCH 3.16 105/346] nfs: don't create zero-length requests

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Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Weston Andros Adamson" <dros@...marydata.com>,
        "Benjamin Coddington" <bcodding@...hat.com>,
        "Trond Myklebust" <trond.myklebust@...marydata.com>,
        "Alexey Dobriyan" <adobriyan@...il.com>
Subject: [PATCH 3.16 105/346] nfs: don't create zero-length requests

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Benjamin Coddington <bcodding@...hat.com>

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@...hat.com>
Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
Reviewed-by: Weston Andros Adamson <dros@...marydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...marydata.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nfs/write.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1222,6 +1222,9 @@ int nfs_updatepage(struct file *file, st
 	dprintk("NFS:       nfs_updatepage(%pD2 %d@...d)\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, st
 		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;