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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2017-08-23 19:10:30 +02:00 committed by Jens Axboe
parent de65b01232
commit 807d4af2f6
2 changed files with 15 additions and 13 deletions
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2
block/blk.h
View File

@ -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 *);

26
block/genhd.c
View File

@ -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]);
if (part)
get_device(part_to_dev(part));
}
part = __disk_get_part(disk, partno);
if (part)
get_device(part_to_dev(part));
rcu_read_unlock();
return part;