Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Jens Axboe <axboe@kernel.dk>
To:     io-uring@vger.kernel.org
Cc:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, akpm@linux-foundation.org,
        Jens Axboe <axboe@kernel.dk>
Subject: [PATCH 01/15] block: provide plug based way of signaling forced no-wait semantics
Date:   Thu, 18 Jun 2020 08:43:41 -0600
Message-Id: <20200618144355.17324-2-axboe@kernel.dk>
In-Reply-To: <20200618144355.17324-1-axboe@kernel.dk>
References: <20200618144355.17324-1-axboe@kernel.dk>
Reply-To: "[PATCHSET v7 0/15]"@vger.kernel.org, Add@vger.kernel.org,
          support@vger.kernel.org, for@vger.kernel.org,
          async@vger.kernel.org, buffered@vger.kernel.org,
          reads@vger.kernel.org
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Provide a way for the caller to specify that IO should be marked
with REQ_NOWAIT to avoid blocking on allocation.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-core.c       | 6 ++++++
 include/linux/blkdev.h | 1 +
 2 files changed, 7 insertions(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index 03252af8c82c..62a4904db921 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -958,6 +958,7 @@ generic_make_request_checks(struct bio *bio)
 	struct request_queue *q;
 	int nr_sectors = bio_sectors(bio);
 	blk_status_t status = BLK_STS_IOERR;
+	struct blk_plug *plug;
 	char b[BDEVNAME_SIZE];
 
 	might_sleep();
@@ -971,6 +972,10 @@ generic_make_request_checks(struct bio *bio)
 		goto end_io;
 	}
 
+	plug = blk_mq_plug(q, bio);
+	if (plug && plug->nowait)
+		bio->bi_opf |= REQ_NOWAIT;
+
 	/*
 	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP
 	 * if queue is not a request based queue.
@@ -1800,6 +1805,7 @@ void blk_start_plug(struct blk_plug *plug)
 	INIT_LIST_HEAD(&plug->cb_list);
 	plug->rq_count = 0;
 	plug->multiple_queues = false;
+	plug->nowait = false;
 
 	/*
 	 * Store ordering should not be needed here, since a potential
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8fd900998b4e..6e067dca94cf 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1189,6 +1189,7 @@ struct blk_plug {
 	struct list_head cb_list; /* md requires an unplug callback */
 	unsigned short rq_count;
 	bool multiple_queues;
+	bool nowait;
 };
 #define BLK_MAX_REQUEST_COUNT 16
 #define BLK_PLUG_FLUSH_SIZE (128 * 1024)
-- 
2.27.0