linux-kernel - [PATCH 3.12 080/100] nfs: don't create zero-length requests

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Date:   Fri, 19 Aug 2016 09:11:19 +0200
From:   Jiri Slaby <jslaby@...e.cz>
To:     stable@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Benjamin Coddington <bcodding@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Trond Myklebust <trond.myklebust@...marydata.com>,
        Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 080/100] nfs: don't create zero-length requests

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

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 fs/nfs/write.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 3a1b1d1a27ce..d194a72b5b66 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -967,6 +967,9 @@ int nfs_updatepage(struct file *file, struct page *page,
 		file->f_path.dentry->d_name.name, 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;
@@ -977,7 +980,7 @@ 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;
-- 
2.9.3