Commit 807d4af2 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: add a __disk_get_part helper 



This helper allows looking up a partion under RCU protection without
grabbing a reference to it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent de65b012

block/blk.h

+2 −0
Original line number Diff line number Diff line
@@ -204,6 +204,8 @@ static inline void elv_deactivate_rq(struct request_queue *q, struct request *rq 
		e->type->ops.sq.elevator_deactivate_req_fn(q, rq);

}



struct hd_struct *__disk_get_part(struct gendisk *disk, int partno);



#ifdef CONFIG_FAIL_IO_TIMEOUT

int blk_should_fake_timeout(struct request_queue *);

ssize_t part_timeout_show(struct device *, struct device_attribute *, char *);

block/genhd.c

+13 −13
Original line number Diff line number Diff line
@@ -82,6 +82,15 @@ void part_in_flight(struct request_queue *q, struct hd_struct *part, 
	}

}



struct hd_struct *__disk_get_part(struct gendisk *disk, int partno)

{

	struct disk_part_tbl *ptbl = rcu_dereference(disk->part_tbl);



	if (unlikely(partno < 0 || partno >= ptbl->len))

		return NULL;

	return rcu_dereference(ptbl->part[partno]);

}



/**

 * disk_get_part - get partition

 * @disk: disk to look partition from
@@ -98,21 +107,12 @@ void part_in_flight(struct request_queue *q, struct hd_struct *part, 
 */

struct hd_struct *disk_get_part(struct gendisk *disk, int partno)

{

	struct hd_struct *part = NULL;

	struct disk_part_tbl *ptbl;



	if (unlikely(partno < 0))

		return NULL;

	struct hd_struct *part;



	rcu_read_lock();



	ptbl = rcu_dereference(disk->part_tbl);

	if (likely(partno < ptbl->len)) {

		part = rcu_dereference(ptbl->part[partno]);

	part = __disk_get_part(disk, partno);

	if (part)

		get_device(part_to_dev(part));

	}



	rcu_read_unlock();



	return part;