From b86054540e4ad7d8df67f3a80658d037a2ce1c02 Mon Sep 17 00:00:00 2001
From: Omar Sandoval <osandov@osandov.com>
Date: Tue, 24 Feb 2015 02:47:06 -0800
Subject: [PATCH] btrfs: check io_ctl_prepare_pages return in
 __btrfs_write_out_cache

If io_ctl_prepare_pages fails, the pages in io_ctl.pages are not valid.
When we try to access them later, things will blow up in various ways.

Also fix the comment about the return value, which is an errno on error,
not -1, and update the cases where it was not.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Chris Mason <clm@fb.com>
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