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authorDamien Le Moal <damien.lemoal@wdc.com>2019-09-05 18:51:31 +0900
committerJens Axboe <axboe@kernel.dk>2019-09-05 19:52:33 -0600
commit68c43f133a754c7bf5cb1018bb16dc0821cc43a1 (patch)
tree79d8eba4264de5d90e3f8bedd2329e5802c94b6e /block/blk-settings.c
parent954b4a5ce4a806e7c284ce6b2659abdd03d0b6e2 (diff)
block: Introduce elevator features
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>
Diffstat (limited to 'block/blk-settings.c')
-rw-r--r--block/blk-settings.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/block/blk-settings.c b/block/blk-settings.c
index a058997b9cce..6bd1e3b082d8 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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;