diff options
author | Tejun Heo <tj@kernel.org> | 2011-12-14 00:33:42 +0100 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2011-12-14 00:33:42 +0100 |
commit | f1f8cc94651738b418ba54c039df536303b91704 (patch) | |
tree | eb8bc5a33dec104ab32a935a5bb1e1da2e7cdd34 /include/linux/elevator.h | |
parent | 9b84cacd013996f244d85b3d873287c2a8f88658 (diff) | |
download | linux-stable-f1f8cc94651738b418ba54c039df536303b91704.tar.gz linux-stable-f1f8cc94651738b418ba54c039df536303b91704.tar.bz2 linux-stable-f1f8cc94651738b418ba54c039df536303b91704.zip |
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.h | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/include/linux/elevator.h b/include/linux/elevator.h index c8f1e67a8ebe..c24f3d7fbf1e 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; |