cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue()
authorTejun Heo <tj@kernel.org>
Tue, 18 Aug 2015 21:55:02 +0000 (14:55 -0700)
committerJens Axboe <axboe@fb.com>
Tue, 18 Aug 2015 22:49:16 +0000 (15:49 -0700)
commit2da8de0bb799bf2bdfa893e5a1e294eb6bafba62
tree6f8898af2df9a9bd687e97b08a0d7cdbc52dcd17
parentd93a11f1cd890d4ea72f7cef75fac56801b099b3
cfq-iosched: remove @gfp_mask from cfq_find_alloc_queue()

Even when allocations fail, cfq_find_alloc_queue() always returns a
valid cfq_queue by falling back to the oom cfq_queue.  As such, there
isn't much point in taking @gfp_mask and trying "harder" if __GFP_WAIT
is set.  GFP_NOWAIT allocations don't fail often and even when they do
the degraded behavior is acceptable and temporary.

After all, the only reason get_request(), which ultimately determines
the gfp_mask, cares about __GFP_WAIT is to guarantee request
allocation, assuming IO forward progress, for callers which are
willing to wait.  There's no reason for cfq_find_alloc_queue() to
behave differently on __GFP_WAIT when it already has a fallback
mechanism.

Remove @gfp_mask from cfq_find_alloc_queue() and propagate the changes
to its callers.  This simplifies the function quite a bit and will
help making async queues per-cfq_group.

v2: Updated to reflect GFP_ATOMIC -> GPF_NOWAIT.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
block/cfq-iosched.c