tree 6966f1b059f1bdadc0d679067796d9b4bf9a22c3
parent d5036d770f871bd34c9cfd955e6dee692e1e8e81
author Jens Axboe <jens.axboe@oracle.com> 1246347252 +0200
committer Jens Axboe <jens.axboe@oracle.com> 1246438585 +0200

cfq-iosched: get rid of the need for __GFP_NOFAIL in cfq_find_alloc_queue()

Setup an emergency fallback cfqq that we allocate at IO scheduler init
time. If the slab allocation fails in cfq_find_alloc_queue(), we'll just
punt IO to that cfqq instead. This ensures that cfq_find_alloc_queue()
never fails without having to ensure free memory.

On cfqq lookup, always try to allocate a new cfqq if the given cfq io
context has the oom_cfqq assigned. This ensures that we only temporarily
punt to this shared queue.

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>