linux-kernel - [PATCH v2 2/6] blk-mq: Add a flag for reserved requests

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Date:   Tue, 21 Jun 2022 19:15:39 +0800
From:   John Garry <john.garry@...wei.com>
To:     <axboe@...nel.dk>, <damien.lemoal@...nsource.wdc.com>,
        <bvanassche@....org>, <hch@....de>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <hare@...e.de>, <satishkh@...co.com>,
        <sebaddel@...co.com>, <kartilak@...co.com>
CC:     <linux-doc@...r.kernel.org>, <linux-rdma@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>, <linux-nvme@...ts.infradead.org>,
        <linux-s390@...r.kernel.org>, <linux-scsi@...r.kernel.org>,
        <mpi3mr-linuxdrv.pdl@...adcom.com>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <nbd@...er.debian.org>,
        John Garry <john.garry@...wei.com>
Subject: [PATCH v2 2/6] blk-mq: Add a flag for reserved requests

Add a flag for reserved requests so that drivers may know this for any
special handling.

Signed-off-by: John Garry <john.garry@...wei.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Bart Van Assche <bvanassche@....org>
Reviewed-by: Hannes Reinecke <hare@...e.de>
---
 block/blk-mq.c         | 6 ++++++
 include/linux/blk-mq.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5aa95964191b..d38c97fe89f5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -474,6 +474,9 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
 	if (!(data->rq_flags & RQF_ELV))
 		blk_mq_tag_busy(data->hctx);
 
+	if (data->flags & BLK_MQ_REQ_RESERVED)
+		data->rq_flags |= RQF_RESV;
+
 	/*
 	 * Try batched alloc if we want more than 1 tag.
 	 */
@@ -588,6 +591,9 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 	else
 		data.rq_flags |= RQF_ELV;
 
+	if (flags & BLK_MQ_REQ_RESERVED)
+		data.rq_flags |= RQF_RESV;
+
 	ret = -EWOULDBLOCK;
 	tag = blk_mq_get_tag(&data);
 	if (tag == BLK_MQ_NO_TAG)
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index e2d9daf7e8dd..6d81fe10e850 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -57,6 +57,7 @@ typedef __u32 __bitwise req_flags_t;
 #define RQF_TIMED_OUT		((__force req_flags_t)(1 << 21))
 /* queue has elevator attached */
 #define RQF_ELV			((__force req_flags_t)(1 << 22))
+#define RQF_RESV			((__force req_flags_t)(1 << 23))
 
 /* flags that prevent us from merging requests: */
 #define RQF_NOMERGE_FLAGS \
@@ -823,6 +824,11 @@ static inline bool blk_mq_need_time_stamp(struct request *rq)
 	return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS | RQF_ELV));
 }
 
+static inline bool blk_mq_is_reserved_rq(struct request *rq)
+{
+	return rq->rq_flags & RQF_RESV;
+}
+
 /*
  * Batched completions only work when there is no I/O error and no special
  * ->end_io handler.
-- 
2.25.1