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Commit 6c71013e authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: partition: convert percpu ref 



Percpu refcount is the perfect match for partition's case,
and the conversion is quite straight.

With the convertion, one pair of atomic inc/dec can be saved
for accounting block I/O, which is run in hot path of block I/O.

Signed-off-by: default avatarMing Lei <tom.leiming@gmail.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent b54e5ed8

block/genhd.c

+5 −1
Original line number Diff line number Diff line
@@ -1284,7 +1284,11 @@ struct gendisk *alloc_disk_node(int minors, int node_id) 
		 * converted to make use of bd_mutex and sequence counters.

		 */

		seqcount_init(&disk->part0.nr_sects_seq);

		hd_ref_init(&disk->part0);

		if (hd_ref_init(&disk->part0)) {

			hd_free_part(&disk->part0);

			kfree(disk);

			return NULL;

		}



		disk->minors = minors;

		rand_initialize_disk(disk);

block/partition-generic.c

+5 −4
Original line number Diff line number Diff line
@@ -232,8 +232,9 @@ static void delete_partition_rcu_cb(struct rcu_head *head) 
	put_device(part_to_dev(part));

}



void __delete_partition(struct hd_struct *part)

void __delete_partition(struct percpu_ref *ref)

{

	struct hd_struct *part = container_of(ref, struct hd_struct, ref);

	call_rcu(&part->rcu_head, delete_partition_rcu_cb);

}
@@ -254,7 +255,7 @@ void delete_partition(struct gendisk *disk, int partno) 
	kobject_put(part->holder_dir);

	device_del(part_to_dev(part));



	hd_struct_put(part);

	hd_struct_kill(part);

}



static ssize_t whole_disk_show(struct device *dev,
@@ -355,7 +356,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno, 
	if (!dev_get_uevent_suppress(ddev))

		kobject_uevent(&pdev->kobj, KOBJ_ADD);



	hd_ref_init(p);

	if (!hd_ref_init(p))

		return p;



out_free_info:

include/linux/genhd.h

+17 −10
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/kdev_t.h>

#include <linux/rcupdate.h>

#include <linux/slab.h>

#include <linux/percpu-refcount.h>



#ifdef CONFIG_BLOCK
@@ -124,7 +125,7 @@ struct hd_struct { 
#else

	struct disk_stats dkstats;

#endif

	atomic_t ref;

	struct percpu_ref ref;

	struct rcu_head rcu_head;

};
@@ -611,7 +612,7 @@ extern struct hd_struct * __must_check add_partition(struct gendisk *disk, 
						     sector_t len, int flags,

						     struct partition_meta_info

						       *info);

extern void __delete_partition(struct hd_struct *);

extern void __delete_partition(struct percpu_ref *);

extern void delete_partition(struct gendisk *, int);

extern void printk_all_partitions(void);
@@ -640,33 +641,39 @@ extern ssize_t part_fail_store(struct device *dev, 
			       const char *buf, size_t count);

#endif /* CONFIG_FAIL_MAKE_REQUEST */



static inline void hd_ref_init(struct hd_struct *part)

static inline int hd_ref_init(struct hd_struct *part)

{

	atomic_set(&part->ref, 1);

	smp_mb();

	if (percpu_ref_init(&part->ref, __delete_partition, 0,

				GFP_KERNEL))

		return -ENOMEM;

	return 0;

}



static inline void hd_struct_get(struct hd_struct *part)

{

	atomic_inc(&part->ref);

	smp_mb__after_atomic();

	percpu_ref_get(&part->ref);

}



static inline int hd_struct_try_get(struct hd_struct *part)

{

	return atomic_inc_not_zero(&part->ref);

	return percpu_ref_tryget_live(&part->ref);

}



static inline void hd_struct_put(struct hd_struct *part)

{

	if (atomic_dec_and_test(&part->ref))

		__delete_partition(part);

	percpu_ref_put(&part->ref);

}



static inline void hd_struct_kill(struct hd_struct *part)

{

	percpu_ref_kill(&part->ref);

}



static inline void hd_free_part(struct hd_struct *part)

{

	free_part_stats(part);

	free_part_info(part);

	percpu_ref_exit(&part->ref);

}



/*