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block, cfq: move io_cq exit/release to blk-ioc.c

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With kmem_cache managed by blk-ioc, io_cq exit/release can be moved to
blk-ioc too.  The odd ->io_cq->exit/release() callbacks are replaced
with elevator_ops->elevator_exit_icq_fn() with unlinking from both ioc
and q, and freeing automatically handled by blk-ioc.  The elevator
operation only need to perform exit operation specific to the elevator
- in cfq's case, exiting the cfqq's.

Also, clearing of io_cq's on q detach is moved to block core and
automatically performed on elevator switch and q release.

Because the q io_cq points to might be freed before RCU callback for
the io_cq runs, blk-ioc code should remember to which cache the io_cq
needs to be freed when the io_cq is released.  New field
io_cq->__rcu_icq_cache is added for this purpose.  As both the new
field and rcu_head are used only after io_cq is released and the
q/ioc_node fields aren't, they are put into unions.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2011-12-14 00:33:42 +01:00 • committed by Jens Axboe
parent 3d3c2379fe
commit 7e5a879449
7 changed files with 97 additions and 61 deletions
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20
include/linux/iocontext.h
View file

@ -14,14 +14,22 @@ struct io_cq {
struct request_queue *q;
struct io_context *ioc;
struct list_head q_node;
struct hlist_node ioc_node;
/*
* q_node and ioc_node link io_cq through icq_list of q and ioc
* respectively. Both fields are unused once ioc_exit_icq() is
* called and shared with __rcu_icq_cache and __rcu_head which are
* used for RCU free of io_cq.
*/
union {
struct list_head q_node;
struct kmem_cache *__rcu_icq_cache;
};
union {
struct hlist_node ioc_node;
struct rcu_head __rcu_head;
};
unsigned long changed;
struct rcu_head rcu_head;
void (*exit)(struct io_cq *);
void (*release)(struct io_cq *);
};
/*