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percpu_ida: add an API to return free tags

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Add an API to return free tags, blk-mq-tag will use it.

Note, this just returns a snapshot of free tags number. blk-mq-tag has
two usages of it. One is for info output for diagnosis. The other is to
quickly check if there are free tags for request dispatch checking.
Neither requires very precise.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Shaohua Li
2013-10-15 09:05:03 +08:00
committed by Jens Axboe
parent 7fc2ba17e8
commit 1dddc01af0
2 changed files with 18 additions and 0 deletions
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17
lib/percpu_ida.c
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@@ -371,3 +371,20 @@ out:
return err;
}
EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);
/**
* percpu_ida_free_tags - return free tags number of a specific cpu or global pool
* @pool: pool related
* @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
*
* Note: this just returns a snapshot of free tags number.
*/
unsigned percpu_ida_free_tags(struct percpu_ida *pool, int cpu)
{
struct percpu_ida_cpu *remote;
if (cpu == nr_cpu_ids)
return pool->nr_free;
remote = per_cpu_ptr(pool->tag_cpu, cpu);
return remote->nr_free;
}
EXPORT_SYMBOL_GPL(percpu_ida_free_tags);