From: Mike Snitzer <snitzer@redhat.com>
Date: Thu, 19 Sep 2013 22:49:11 +0000 (-0400)
Subject: dm thin: do not expose non-zero discard limits if discards disabled
X-Git-Tag: v3.12-rc3~25^2~3
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b60ab990ccdf34b0159bf5ff52f4acee7c940d78;p=pandora-kernel.git

dm thin: do not expose non-zero discard limits if discards disabled

Fix issue where the block layer would stack the discard limits of the
pool's data device even if the "ignore_discard" pool feature was
specified.

The pool and thin device(s) still had discards disabled because the
QUEUE_FLAG_DISCARD request_queue flag wasn't set.  But to avoid user
confusion when "ignore_discard" is used: both the pool device and the
thin device(s) have zeroes for all discard limits.

Also, always set discard_zeroes_data_unsupported in targets because they
should never advertise the 'discard_zeroes_data' capability (even if the
pool's data device supports it).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
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