[PATCH V6 4/6] block: prepare for passing RQF_PREEMPT to request allocation

Ming Lei
2017-09-27T05:48:51Z

REQF_PREEMPT is a bit special because the request is required
to be dispatched to lld even when SCSI device is quiesced.

So this patch introduces __blk_get_request() and allows users to pass
RQF_PREEMPT flag in, then we can allow to allocate request of RQF_PREEMPT
when queue is in mode of PREEMPT ONLY which will be introduced
in the following patch.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/blk-core.c | 19 +++++++++----------
block/blk-mq.c | 3 +--
include/linux/blk-mq.h | 7 ++++---
include/linux/blkdev.h | 17 ++++++++++++++---
4 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index be17b5bcf6e7..0a8396e8e4ff 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1395,7 +1395,8 @@ static struct request *get_request(struct request_queue *q, unsigned int op,
}

static struct request *blk_old_get_request(struct request_queue *q,
- unsigned int op, gfp_t gfp_mask)
+ unsigned int op, gfp_t gfp_mask,
+ unsigned int flags)
{
struct request *rq;
int ret = 0;
@@ -1405,8 +1406,7 @@ static struct request *blk_old_get_request(struct request_queue *q,
/* create ioc upfront */
create_io_context(gfp_mask, q->node);

- ret = blk_queue_enter(q, !(gfp_mask & __GFP_DIRECT_RECLAIM) ?
- BLK_REQ_NOWAIT : 0);
+ ret = blk_queue_enter(q, flags & BLK_REQ_BITS_MASK);
if (ret)
return ERR_PTR(ret);
spin_lock_irq(q->queue_lock);
@@ -1424,26 +1424,25 @@ static struct request *blk_old_get_request(struct request_queue *q,
return rq;
}

-struct request *blk_get_request(struct request_queue *q, unsigned int op,
- gfp_t gfp_mask)
+struct request *__blk_get_request(struct request_queue *q, unsigned int op,
+ gfp_t gfp_mask, unsigned int flags)
{
struct request *req;

+ flags |= gfp_mask & __GFP_DIRECT_RECLAIM ? 0 : BLK_REQ_NOWAIT;
if (q->mq_ops) {
- req = blk_mq_alloc_request(q, op,
- (gfp_mask & __GFP_DIRECT_RECLAIM) ?
- 0 : BLK_MQ_REQ_NOWAIT);
+ req = blk_mq_alloc_request(q, op, flags);
if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn)
q->mq_ops->initialize_rq_fn(req);
} else {
- req = blk_old_get_request(q, op, gfp_mask);
+ req = blk_old_get_request(q, op, gfp_mask, flags);
if (!IS_ERR(req) && q->initialize_rq_fn)
q->initialize_rq_fn(req);
}

return req;
}
-EXPORT_SYMBOL(blk_get_request);
+EXPORT_SYMBOL(__blk_get_request);

/**
* blk_requeue_request - put a request back on queue
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 45bff90e08f7..90b43f607e3c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -384,8 +384,7 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
struct request *rq;
int ret;

- ret = blk_queue_enter(q, (flags & BLK_MQ_REQ_NOWAIT) ?
- BLK_REQ_NOWAIT : 0);
+ ret = blk_queue_enter(q, flags & BLK_REQ_BITS_MASK);
if (ret)
return ERR_PTR(ret);

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 50c6485cb04f..066a676d7749 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -197,9 +197,10 @@ void blk_mq_free_request(struct request *rq);
bool blk_mq_can_queue(struct blk_mq_hw_ctx *);

enum {
- BLK_MQ_REQ_NOWAIT = (1 << 0), /* return when out of requests */
- BLK_MQ_REQ_RESERVED = (1 << 1), /* allocate from reserved pool */
- BLK_MQ_REQ_INTERNAL = (1 << 2), /* allocate internal/sched tag */
+ BLK_MQ_REQ_NOWAIT = BLK_REQ_NOWAIT, /* return when out of requests */
+ BLK_MQ_REQ_PREEMPT = BLK_REQ_PREEMPT, /* allocate for RQF_PREEMPT */
+ BLK_MQ_REQ_RESERVED = (1 << BLK_REQ_MQ_START_BIT), /* allocate from reserved pool */
+ BLK_MQ_REQ_INTERNAL = (1 << (BLK_REQ_MQ_START_BIT + 1)), /* allocate internal/sched tag */
};

struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 107e2fd48486..d1ab950a7f72 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -859,7 +859,10 @@ enum {

/* passed to blk_queue_enter */
enum {
- BLK_REQ_NOWAIT = (1 << 0),
+ BLK_REQ_NOWAIT = (1 << 0),
+ BLK_REQ_PREEMPT = (1 << 1),
+ BLK_REQ_MQ_START_BIT = 2,
+ BLK_REQ_BITS_MASK = (1U << BLK_REQ_MQ_START_BIT) - 1,
};

extern unsigned long blk_max_low_pfn, blk_max_pfn;
@@ -944,8 +947,9 @@ extern void blk_rq_init(struct request_queue *q, struct request *rq);
extern void blk_init_request_from_bio(struct request *req, struct bio *bio);
extern void blk_put_request(struct request *);
extern void __blk_put_request(struct request_queue *, struct request *);
-extern struct request *blk_get_request(struct request_queue *, unsigned int op,
- gfp_t gfp_mask);
+extern struct request *__blk_get_request(struct request_queue *,
+ unsigned int op, gfp_t gfp_mask,
+ unsigned int flags);
extern void blk_requeue_request(struct request_queue *, struct request *);
extern int blk_lld_busy(struct request_queue *q);
extern int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
@@ -996,6 +1000,13 @@ blk_status_t errno_to_blk_status(int errno);

bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie);

+static inline struct request *blk_get_request(struct request_queue *q,
+ unsigned int op,
+ gfp_t gfp_mask)
+{
+ return __blk_get_request(q, op, gfp_mask, 0);
+}
+
static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
{
return bdev->bd_disk->queue; /* this is never NULL */
--
2.9.5