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ANDROID: block: Introduce a request queue flag for pipelining zoned writes

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Writes in sequential write required zones must happen at the write
pointer. Even if the submitter of the write commands (e.g. a filesystem)
submits writes for sequential write required zones in order, the block
layer or the storage controller may reorder these write commands.

The zone locking mechanism in the mq-deadline I/O scheduler serializes
write commands for sequential zones. Some but not all storage controllers
require this serialization. Introduce a new flag such that block drivers
can request pipelining of writes for sequential write required zones.

An example of a storage controller standard that requires write
serialization is AHCI (Advanced Host Controller Interface). Submitting
commands to AHCI controllers happens by writing a bit pattern into a
register. Each set bit corresponds to an active command. This mechanism
does not preserve command ordering information.

Bug: 264714656
Change-Id: I1f64eb61571a66b99a0d83bef4438e2187c16f8e
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2023-01-06 17:02:50 -08:00
parent d4f3dbfe1b
commit 54678c4c75
1 changed files with 7 additions and 0 deletions
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7
include/linux/blkdev.h
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@@ -607,6 +607,8 @@ struct request_queue {
#define QUEUE_FLAG_RQ_ALLOC_TIME 27 /* record rq->alloc_time_ns */
#define QUEUE_FLAG_HCTX_ACTIVE 28 /* at least one blk-mq hctx is active */
#define QUEUE_FLAG_NOWAIT 29 /* device supports NOWAIT */
/* Pipeline zoned writes (REQ_OP_WRITE, REQ_OP_WRITE_ZEROES). */
#define QUEUE_FLAG_PIPELINE_ZONED_WRITES 30
#define QUEUE_FLAG_MQ_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_SAME_COMP) | \
@@ -654,6 +656,11 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
#define blk_queue_registered(q) test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
#define blk_queue_nowait(q) test_bit(QUEUE_FLAG_NOWAIT, &(q)->queue_flags)
static inline bool blk_queue_pipeline_zoned_writes(struct request_queue *q)
{
return test_bit(QUEUE_FLAG_PIPELINE_ZONED_WRITES, &q->queue_flags);
}
extern void blk_set_pm_only(struct request_queue *q);
extern void blk_clear_pm_only(struct request_queue *q);