lkml.org 
[lkml]   [2013]   [Jan]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 20/24] block: RCU free request_queue
    On Fri, Dec 28, 2012 at 12:35:42PM -0800, Tejun Heo wrote:
    > RCU free request_queue so that blkcg_gq->q can be dereferenced under
    > RCU lock. This will be used to implement hierarchical stats.

    Can we just take a blkg reference on ->q in blkg_alloc() and drop that
    reference in blkg_free(), instead of RCU freeing up queue.

    Thanks
    Vivek

    >
    > Signed-off-by: Tejun Heo <tj@kernel.org>
    > ---
    > block/blk-sysfs.c | 9 ++++++++-
    > include/linux/blkdev.h | 2 ++
    > 2 files changed, 10 insertions(+), 1 deletion(-)
    >
    > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
    > index 7881477..6206a93 100644
    > --- a/block/blk-sysfs.c
    > +++ b/block/blk-sysfs.c
    > @@ -497,6 +497,13 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
    > return res;
    > }
    >
    > +static void blk_free_queue_rcu(struct rcu_head *rcu_head)
    > +{
    > + struct request_queue *q = container_of(rcu_head, struct request_queue,
    > + rcu_head);
    > + kmem_cache_free(blk_requestq_cachep, q);
    > +}
    > +
    > /**
    > * blk_release_queue: - release a &struct request_queue when it is no longer needed
    > * @kobj: the kobj belonging to the request queue to be released
    > @@ -538,7 +545,7 @@ static void blk_release_queue(struct kobject *kobj)
    > bdi_destroy(&q->backing_dev_info);
    >
    > ida_simple_remove(&blk_queue_ida, q->id);
    > - kmem_cache_free(blk_requestq_cachep, q);
    > + call_rcu(&q->rcu_head, blk_free_queue_rcu);
    > }
    >
    > static const struct sysfs_ops queue_sysfs_ops = {
    > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
    > index f94bc83..406343c 100644
    > --- a/include/linux/blkdev.h
    > +++ b/include/linux/blkdev.h
    > @@ -19,6 +19,7 @@
    > #include <linux/gfp.h>
    > #include <linux/bsg.h>
    > #include <linux/smp.h>
    > +#include <linux/rcupdate.h>
    >
    > #include <asm/scatterlist.h>
    >
    > @@ -437,6 +438,7 @@ struct request_queue {
    > /* Throttle data */
    > struct throtl_data *td;
    > #endif
    > + struct rcu_head rcu_head;
    > };
    >
    > #define QUEUE_FLAG_QUEUED 1 /* uses generic tag queueing */
    > --
    > 1.8.0.2


    \
     
     \ /
      Last update: 2013-01-02 20:41    [W:2.664 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site