summaryrefslogtreecommitdiffstats
path: root/include/linux/elevator.h
diff options
context:
space:
mode:
authorTejun Heo <tj@kernel.org>2011-12-14 00:33:42 +0100
committerJens Axboe <axboe@kernel.dk>2011-12-14 00:33:42 +0100
commitf1f8cc94651738b418ba54c039df536303b91704 (patch)
treeeb8bc5a33dec104ab32a935a5bb1e1da2e7cdd34 /include/linux/elevator.h
parent9b84cacd013996f244d85b3d873287c2a8f88658 (diff)
downloadop-kernel-dev-f1f8cc94651738b418ba54c039df536303b91704.zip
op-kernel-dev-f1f8cc94651738b418ba54c039df536303b91704.tar.gz
block, cfq: move icq creation and rq->elv.icq association to block core
Now block layer knows everything necessary to create and associate icq's with requests. Move ioc_create_icq() to blk-ioc.c and update get_request() such that, if elevator_type->icq_size is set, requests are automatically associated with their matching icq's before elv_set_request(). io_context reference is also managed by block core on request alloc/free. * Only ioprio/cgroup changed handling remains from cfq_get_cic(). Collapsed into cfq_set_request(). * This removes queue kicking on icq allocation failure (for now). As icq allocation failure is rare and the only effect of queue kicking achieved was possibily accelerating queue processing, this change shouldn't be noticeable. There is a larger underlying problem. Unlike request allocation, icq allocation is not guaranteed to succeed eventually after retries. The number of icq is unbound and thus mempool can't be the solution either. This effectively adds allocation dependency on memory free path and thus possibility of deadlock. This usually wouldn't happen because icq allocation is not a hot path and, even when the condition triggers, it's highly unlikely that none of the writeback workers already has icq. However, this is still possible especially if elevator is being switched under high memory pressure, so we better get it fixed. Probably the only solution is just bypassing elevator and appending to dispatch queue on any elevator allocation failure. * Comment added to explain how icq's are managed and synchronized. This completes cleanup of io_context interface. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/elevator.h')
-rw-r--r--include/linux/elevator.h8
1 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index c8f1e67..c24f3d7 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -60,8 +60,8 @@ struct elevator_ops
elevator_request_list_fn *elevator_former_req_fn;
elevator_request_list_fn *elevator_latter_req_fn;
- elevator_init_icq_fn *elevator_init_icq_fn;
- elevator_exit_icq_fn *elevator_exit_icq_fn;
+ elevator_init_icq_fn *elevator_init_icq_fn; /* see iocontext.h */
+ elevator_exit_icq_fn *elevator_exit_icq_fn; /* ditto */
elevator_set_req_fn *elevator_set_req_fn;
elevator_put_req_fn *elevator_put_req_fn;
@@ -90,8 +90,8 @@ struct elevator_type
/* fields provided by elevator implementation */
struct elevator_ops ops;
- size_t icq_size;
- size_t icq_align;
+ size_t icq_size; /* see iocontext.h */
+ size_t icq_align; /* ditto */
struct elv_fs_entry *elevator_attrs;
char elevator_name[ELV_NAME_MAX];
struct module *elevator_owner;
OpenPOWER on IntegriCloud