67320f56fc4d549875b6f3a6940018ef2e5 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Tue, 30 Aug 2016 16:20:55 -0400
Subject: dm log writes: fix bug with too large bios

bio_alloc() can allocate a bio with at most BIO_MAX_PAGES (256) vector
entries.  However, the incoming bio may have more vector entries if it
was allocated by other means.  For example, bcache submits bios with
more than BIO_MAX_PAGES entries.  This results in bio_alloc() failure.

To avoid the failure, change the code so that it allocates bio with at
most BIO_MAX_PAGES entries.  If the incoming bio has more entries,
bio_add_page() will fail and a new bio will be allocated - the code that
handles bio_add_page() failure already exists in the dm-log-writes
target.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Josef Bacik <jbacik@fb,com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v4.1+
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