tree d6e1cdc5f18f6c8025d4fb6415e682bb0b60dd29
parent df35c7c912fe668797681842b3b74c61b0664050
author Jens Axboe <axboe@fb.com> 1410361323 -0600
committer Jens Axboe <axboe@fb.com> 1410361323 -0600

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>