From: Scott Mayhew <smayhew@redhat.com>
Date: Fri, 17 Jan 2014 20:12:05 +0000 (-0500)
Subject: nfs: always make sure page is up-to-date before extending a write to cover the entire... 
X-Git-Tag: v3.14-rc1~77^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=263b4509ec4d47e0da3e753f85a39ea12d1eff24;p=pandora-kernel.git

nfs: always make sure page is up-to-date before extending a write to cover the entire page

We should always make sure the cached page is up-to-date when we're
determining whether we can extend a write to cover the full page -- even
if we've received a write delegation from the server.

Commit c7559663 added logic to skip this check if we have a write
delegation, which can lead to data corruption such as the following
scenario if client B receives a write delegation from the NFS server:

Client A:
    # echo 123456789 > /mnt/file

Client B:
    # echo abcdefghi >> /mnt/file
    # cat /mnt/file
    0�D0�abcdefghi

Just because we hold a write delegation doesn't mean that we've read in
the entire page contents.

Cc: <stable@vger.kernel.org> # v3.11+
Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---

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