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block: Introduce elevator features

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Introduce the definition of elevator features through the
elevator_features flags in the elevator_type structure. Each flag can
represent a feature supported by an elevator. The first feature defined
by this patch is support for zoned block device sequential write
constraint with the flag ELEVATOR_F_ZBD_SEQ_WRITE, which is implemented
by the mq-deadline elevator using zone write locking.

Other possible features are IO priorities, write hints, latency targets
or single-LUN dual-actuator disks (for which the elevator could maintain
one LBA ordered list per actuator).

The required_elevator_features field is also added to the request_queue
structure to allow a device driver to specify elevator feature flags
that an elevator must support for the correct operation of the device
(e.g. device drivers for zoned block devices can have the
ELEVATOR_F_ZBD_SEQ_WRITE flag as a required feature).
The helper function blk_queue_required_elevator_features() is
defined for setting this new field.

With these two new fields in place, the elevator functions
elevator_match() and elevator_find() are modified to allow a user to set
only an elevator with a set of features that satisfies the device
required features. Elevators not matching the device requirements are
not shown in the device sysfs queue/scheduler file to prevent their use.

The "none" elevator can always be selected as before.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Damien Le Moal 2019-09-05 18:51:31 +09:00 committed by Jens Axboe
parent 954b4a5ce4
commit 68c43f133a
5 changed files with 67 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
block/blk-settings.c
View File

@ -832,6 +832,22 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
}
EXPORT_SYMBOL_GPL(blk_queue_write_cache);
/**
* blk_queue_required_elevator_features - Set a queue required elevator features
* @q: the request queue for the target device
* @features: Required elevator features OR'ed together
*
* Tell the block layer that for the device controlled through @q, only the
* only elevators that can be used are those that implement at least the set of
* features specified by @features.
*/
void blk_queue_required_elevator_features(struct request_queue *q,
unsigned int features)
{
q->required_elevator_features = features;
}
EXPORT_SYMBOL_GPL(blk_queue_required_elevator_features);
static int __init blk_settings_init(void)
{
blk_max_low_pfn = max_low_pfn - 1;

49
block/elevator.c
View File

@ -83,8 +83,26 @@ bool elv_bio_merge_ok(struct request *rq, struct bio *bio)
}
EXPORT_SYMBOL(elv_bio_merge_ok);
static bool elevator_match(const struct elevator_type *e, const char *name)
static inline bool elv_support_features(unsigned int elv_features,
unsigned int required_features)
{
return (required_features & elv_features) == required_features;
}
/**
* elevator_match - Test an elevator name and features
* @e: Scheduler to test
* @name: Elevator name to test
* @required_features: Features that the elevator must provide
*
* Return true is the elevator @e name matches @name and if @e provides all the
* the feratures spcified by @required_features.
*/
static bool elevator_match(const struct elevator_type *e, const char *name,
unsigned int required_features)
{
if (!elv_support_features(e->elevator_features, required_features))
return false;
if (!strcmp(e->elevator_name, name))
return true;
if (e->elevator_alias && !strcmp(e->elevator_alias, name))
@ -93,15 +111,21 @@ static bool elevator_match(const struct elevator_type *e, const char *name)
return false;
}
/*
* Return scheduler with name 'name'
/**
* elevator_find - Find an elevator
* @name: Name of the elevator to find
* @required_features: Features that the elevator must provide
*
* Return the first registered scheduler with name @name and supporting the
* features @required_features and NULL otherwise.
*/
static struct elevator_type *elevator_find(const char *name)
static struct elevator_type *elevator_find(const char *name,
unsigned int required_features)
{
struct elevator_type *e;
list_for_each_entry(e, &elv_list, list) {
if (elevator_match(e, name))
if (elevator_match(e, name, required_features))
return e;
}
@ -120,12 +144,12 @@ static struct elevator_type *elevator_get(struct request_queue *q,
spin_lock(&elv_list_lock);
e = elevator_find(name);
e = elevator_find(name, q->required_elevator_features);
if (!e && try_loading) {
spin_unlock(&elv_list_lock);
request_module("%s-iosched", name);
spin_lock(&elv_list_lock);
e = elevator_find(name);
e = elevator_find(name, q->required_elevator_features);
}
if (e && !try_module_get(e->elevator_owner))
@ -525,7 +549,7 @@ int elv_register(struct elevator_type *e)
/* register, don't allow duplicate names */
spin_lock(&elv_list_lock);
if (elevator_find(e->elevator_name)) {
if (elevator_find(e->elevator_name, 0)) {
spin_unlock(&elv_list_lock);
kmem_cache_destroy(e->icq_cache);
return -EBUSY;
@ -709,7 +733,8 @@ static int __elevator_change(struct request_queue *q, const char *name)
if (!e)
return -EINVAL;
if (q->elevator && elevator_match(q->elevator->type, elevator_name)) {
if (q->elevator &&
elevator_match(q->elevator->type, elevator_name, 0)) {
elevator_put(e);
return 0;
}
@ -749,11 +774,13 @@ ssize_t elv_iosched_show(struct request_queue *q, char *name)
spin_lock(&elv_list_lock);
list_for_each_entry(__e, &elv_list, list) {
if (elv && elevator_match(elv, __e->elevator_name)) {
if (elv && elevator_match(elv, __e->elevator_name, 0)) {
len += sprintf(name+len, "[%s] ", elv->elevator_name);
continue;
}
if (elv_support_iosched(q))
if (elv_support_iosched(q) &&
elevator_match(__e, __e->elevator_name,
q->required_elevator_features))
len += sprintf(name+len, "%s ", __e->elevator_name);
}
spin_unlock(&elv_list_lock);

1
block/mq-deadline.c
View File

@ -794,6 +794,7 @@ static struct elevator_type mq_deadline = {
.elevator_attrs = deadline_attrs,
.elevator_name = "mq-deadline",
.elevator_alias = "deadline",
.elevator_features = ELEVATOR_F_ZBD_SEQ_WRITE,
.elevator_owner = THIS_MODULE,
};
MODULE_ALIAS("mq-deadline-iosched");

4
include/linux/blkdev.h
View File

@ -496,6 +496,8 @@ struct request_queue {
struct queue_limits limits;
unsigned int required_elevator_features;
#ifdef CONFIG_BLK_DEV_ZONED
/*
* Zoned block device information for request dispatch control.
@ -1097,6 +1099,8 @@ extern void blk_queue_dma_alignment(struct request_queue *, int);
extern void blk_queue_update_dma_alignment(struct request_queue *, int);
extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);
extern void blk_queue_required_elevator_features(struct request_queue *q,
unsigned int features);
/*
* Number of physical segments as sent to the device.

8
include/linux/elevator.h
View File

@ -76,6 +76,7 @@ struct elevator_type
struct elv_fs_entry *elevator_attrs;
const char *elevator_name;
const char *elevator_alias;
const unsigned int elevator_features;
struct module *elevator_owner;
#ifdef CONFIG_BLK_DEBUG_FS
const struct blk_mq_debugfs_attr *queue_debugfs_attrs;
@ -165,5 +166,12 @@ extern struct request *elv_rb_find(struct rb_root *, sector_t);
#define rq_entry_fifo(ptr) list_entry((ptr), struct request, queuelist)
#define rq_fifo_clear(rq) list_del_init(&(rq)->queuelist)
/*
* Elevator features.
*/
/* Supports zoned block devices sequential write constraint */
#define ELEVATOR_F_ZBD_SEQ_WRITE (1U << 0)
#endif /* CONFIG_BLOCK */
#endif