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author | Jens Axboe <jaxboe@fusionio.com> | 2010-08-23 15:52:19 +0400 |
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committer | Jens Axboe <jaxboe@fusionio.com> | 2010-08-23 15:52:19 +0400 |
commit | 5dd531a03ad721b41911ddb32e6e0481404e7aaf (patch) | |
tree | 3d07d0aa902eb61a575bbc7cc2a57c03431e2b01 | |
parent | 220eb7fd984bfc7e6b4005fdf32efe9cd8af7cf2 (diff) | |
download | linux-5dd531a03ad721b41911ddb32e6e0481404e7aaf.tar.xz |
block: add function call to switch the IO scheduler from a driver
Currently drivers must do an elevator_exit() + elevator_init()
to switch IO schedulers. There are a few problems with this:
- Since commit 1abec4fdbb142e3ccb6ce99832fae42129134a96,
elevator_init() requires a zeroed out q->elevator
pointer. The two existing in-kernel users don't do that.
- It will only work at initialization time, since using the
above two-staged construct does not properly quisce the queue.
So add elevator_change() which takes care of this, and convert
the elv_iosched_store() sysfs interface to use this helper as well.
Reported-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reported-by: Kevin Vigor <kevin@vigor.nu>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
-rw-r--r-- | block/elevator.c | 44 | ||||
-rw-r--r-- | include/linux/elevator.h | 1 |
2 files changed, 32 insertions, 13 deletions
diff --git a/block/elevator.c b/block/elevator.c index ec585c9554d3..205b09a5bd9e 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -1009,18 +1009,19 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) { struct elevator_queue *old_elevator, *e; void *data; + int err; /* * Allocate new elevator */ e = elevator_alloc(q, new_e); if (!e) - return 0; + return -ENOMEM; data = elevator_init_queue(q, e); if (!data) { kobject_put(&e->kobj); - return 0; + return -ENOMEM; } /* @@ -1043,7 +1044,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) __elv_unregister_queue(old_elevator); - if (elv_register_queue(q)) + err = elv_register_queue(q); + if (err) goto fail_register; /* @@ -1056,7 +1058,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name); - return 1; + return 0; fail_register: /* @@ -1071,17 +1073,19 @@ fail_register: queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q); spin_unlock_irq(q->queue_lock); - return 0; + return err; } -ssize_t elv_iosched_store(struct request_queue *q, const char *name, - size_t count) +/* + * Switch this queue to the given IO scheduler. + */ +int elevator_change(struct request_queue *q, const char *name) { char elevator_name[ELV_NAME_MAX]; struct elevator_type *e; if (!q->elevator) - return count; + return -ENXIO; strlcpy(elevator_name, name, sizeof(elevator_name)); e = elevator_get(strstrip(elevator_name)); @@ -1092,13 +1096,27 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name, if (!strcmp(elevator_name, q->elevator->elevator_type->elevator_name)) { elevator_put(e); - return count; + return 0; } - if (!elevator_switch(q, e)) - printk(KERN_ERR "elevator: switch to %s failed\n", - elevator_name); - return count; + return elevator_switch(q, e); +} +EXPORT_SYMBOL(elevator_change); + +ssize_t elv_iosched_store(struct request_queue *q, const char *name, + size_t count) +{ + int ret; + + if (!q->elevator) + return count; + + ret = elevator_change(q, name); + if (!ret) + return count; + + printk(KERN_ERR "elevator: switch to %s failed\n", name); + return ret; } ssize_t elv_iosched_show(struct request_queue *q, char *name) diff --git a/include/linux/elevator.h b/include/linux/elevator.h index 2c958f4fce1e..926b50322a46 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -136,6 +136,7 @@ extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t); extern int elevator_init(struct request_queue *, char *); extern void elevator_exit(struct elevator_queue *); +extern int elevator_change(struct request_queue *, const char *); extern int elv_rq_merge_ok(struct request *, struct bio *); /* |