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elevator: acquire q->sysfs_lock in elevator_change() 

Add locking of q->sysfs_lock into elevator_change() (an exported function)
to ensure it is held to protect q->elevator from elevator_init(), even if
elevator_change() is called from non-sysfs paths.
sysfs path (elv_iosched_store) uses __elevator_change(), non-locking
version, as the lock is already taken by elv_iosched_store().

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tomoki Sekiyama 2013-10-15 16:42:19 -06:00 committed by Jens Axboe
parent eb1c160b22
commit 7c8a3679e3
1 changed files with 14 additions and 2 deletions
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16
block/elevator.c
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@ -965,7 +965,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
/*
* Switch this queue to the given IO scheduler.
*/
int elevator_change(struct request_queue *q, const char *name)
static int __elevator_change(struct request_queue *q, const char *name)
{
char elevator_name[ELV_NAME_MAX];
struct elevator_type *e;
@ -987,6 +987,18 @@ int elevator_change(struct request_queue *q, const char *name)
return elevator_switch(q, e);
}
int elevator_change(struct request_queue *q, const char *name)
{
int ret;
/* Protect q->elevator from elevator_init() */
mutex_lock(&q->sysfs_lock);
ret = __elevator_change(q, name);
mutex_unlock(&q->sysfs_lock);
return ret;
}
EXPORT_SYMBOL(elevator_change);
ssize_t elv_iosched_store(struct request_queue *q, const char *name,
@ -997,7 +1009,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
if (!q->elevator)
return count;
ret = elevator_change(q, name);
ret = __elevator_change(q, name);
if (!ret)
return count;