From: Jens Axboe <axboe@fb.com>
Date: Wed, 10 Sep 2014 15:02:03 +0000 (-0600)
Subject: blk-mq: scale depth and rq map appropriate if low on memory
X-Git-Tag: fixes-for-v3.18-merge-window~132^2
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a516440542afcb9647f88d12c35640baf02d07ea;p=pandora-kernel.git

blk-mq: scale depth and rq map appropriate if low on memory

If we are running in a kdump environment, resources are scarce.
For some SCSI setups with a huge set of shared tags, we run out
of memory allocating what the drivers is asking for. So implement
a scale back logic to reduce the tag depth for those cases, allowing
the driver to successfully load.

We should extend this to detect low memory situations, and implement
a sane fallback for those (1 queue, 64 tags, or something like that).

Tested-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
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