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authorTejun Heo <tj@kernel.org>2011-12-13 18:33:42 -0500
committerJens Axboe <axboe@kernel.dk>2011-12-13 18:33:42 -0500
commitf1f8cc94651738b418ba54c039df536303b91704 (patch)
treeeb8bc5a33dec104ab32a935a5bb1e1da2e7cdd34 /block/blk.h
parent9b84cacd013996f244d85b3d873287c2a8f88658 (diff)
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 'block/blk.h')
-rw-r--r--block/blk.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/block/blk.h b/block/blk.h
index ed4d9bf2ab16..7efd772336de 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -200,6 +200,7 @@ static inline int blk_do_io_stat(struct request *rq)
200 */ 200 */
201void get_io_context(struct io_context *ioc); 201void get_io_context(struct io_context *ioc);
202struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q); 202struct io_cq *ioc_lookup_icq(struct io_context *ioc, struct request_queue *q);
203struct io_cq *ioc_create_icq(struct request_queue *q, gfp_t gfp_mask);
203void ioc_clear_queue(struct request_queue *q); 204void ioc_clear_queue(struct request_queue *q);
204 205
205void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_mask, 206void create_io_context_slowpath(struct task_struct *task, gfp_t gfp_mask,