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From: Christoph Hellwig <hch@lst.de>
To: Jens Axboe <axboe@kernel.dk>
Cc: dm-devel@redhat.com, linux-kernel@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-xtensa@linux-xtensa.org,
	drbd-dev@lists.linbit.com, linuxppc-dev@lists.ozlabs.org,
	linux-bcache@vger.kernel.org, linux-raid@vger.kernel.org,
	linux-nvdimm@lists.01.org, linux-nvme@lists.infradead.org,
	linux-s390@vger.kernel.org
Subject: [PATCH 18/20] block: refator submit_bio_noacct
Date: Mon, 29 Jun 2020 21:39:45 +0200
Message-ID: <20200629193947.2705954-19-hch@lst.de> (raw)
In-Reply-To: <20200629193947.2705954-1-hch@lst.de>

Split out a __submit_bio_noacct helper for the actual de-recursion
algorithm, and simplify the loop by using a continue when we can't
enter the queue for a bio.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-core.c | 131 +++++++++++++++++++++++++----------------------
 1 file changed, 71 insertions(+), 60 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 1caeb01e127768..b82f48c86e6f7a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1085,6 +1085,74 @@ static blk_qc_t do_make_request(struct bio *bio)
 	return ret;
 }
 
+/*
+ * The loop in this function may be a bit non-obvious, and so deserves some
+ * explanation:
+ *
+ *  - Before entering the loop, bio->bi_next is NULL (as all callers ensure
+ *    that), so we have a list with a single bio.
+ *  - We pretend that we have just taken it off a longer list, so we assign
+ *    bio_list to a pointer to the bio_list_on_stack, thus initialising the
+ *    bio_list of new bios to be added.  ->submit_bio() may indeed add some more
+ *    bios through a recursive call to submit_bio_noacct.  If it did, we find a
+ *    non-NULL value in bio_list and re-enter the loop from the top.
+ *  - In this case we really did just take the bio of the top of the list (no
+ *    pretending) and so remove it from bio_list, and call into ->submit_bio()
+ *    again.
+ *
+ * bio_list_on_stack[0] contains bios submitted by the current ->submit_bio.
+ * bio_list_on_stack[1] contains bios that were submitted before the current
+ *	->submit_bio_bio, but that haven't been processed yet.
+ */
+static blk_qc_t __submit_bio_noacct(struct bio *bio)
+{
+	struct bio_list bio_list_on_stack[2];
+	blk_qc_t ret = BLK_QC_T_NONE;
+
+	BUG_ON(bio->bi_next);
+
+	bio_list_init(&bio_list_on_stack[0]);
+	current->bio_list = bio_list_on_stack;
+
+	do {
+		struct request_queue *q = bio->bi_disk->queue;
+		struct bio_list lower, same;
+
+		if (unlikely(bio_queue_enter(bio) != 0))
+			continue;
+
+		/*
+		 * Create a fresh bio_list for all subordinate requests.
+		 */
+		bio_list_on_stack[1] = bio_list_on_stack[0];
+		bio_list_init(&bio_list_on_stack[0]);
+
+		ret = do_make_request(bio);
+
+		/*
+		 * Sort new bios into those for a lower level and those for the
+		 * same level.
+		 */
+		bio_list_init(&lower);
+		bio_list_init(&same);
+		while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
+			if (q == bio->bi_disk->queue)
+				bio_list_add(&same, bio);
+			else
+				bio_list_add(&lower, bio);
+
+		/*
+		 * Now assemble so we handle the lowest level first.
+		 */
+		bio_list_merge(&bio_list_on_stack[0], &lower);
+		bio_list_merge(&bio_list_on_stack[0], &same);
+		bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
+	} while ((bio = bio_list_pop(&bio_list_on_stack[0])));
+
+	current->bio_list = NULL;
+	return ret;
+}
+
 /**
  * submit_bio_noacct - re-submit a bio to the block device layer for I/O
  * @bio:  The bio describing the location in memory and on the device.
@@ -1096,17 +1164,8 @@ static blk_qc_t do_make_request(struct bio *bio)
  */
 blk_qc_t submit_bio_noacct(struct bio *bio)
 {
-	/*
-	 * bio_list_on_stack[0] contains bios submitted by the current
-	 * ->submit_bio.
-	 * bio_list_on_stack[1] contains bios that were submitted before the
-	 * current ->submit_bio_bio, but that haven't been processed yet.
-	 */
-	struct bio_list bio_list_on_stack[2];
-	blk_qc_t ret = BLK_QC_T_NONE;
-
 	if (!submit_bio_checks(bio))
-		goto out;
+		return BLK_QC_T_NONE;
 
 	/*
 	 * We only want one ->submit_bio to be active at a time, else
@@ -1120,58 +1179,10 @@ blk_qc_t submit_bio_noacct(struct bio *bio)
 	 */
 	if (current->bio_list) {
 		bio_list_add(&current->bio_list[0], bio);
-		goto out;
+		return BLK_QC_T_NONE;
 	}
 
-	/* following loop may be a bit non-obvious, and so deserves some
-	 * explanation.
-	 * Before entering the loop, bio->bi_next is NULL (as all callers
-	 * ensure that) so we have a list with a single bio.
-	 * We pretend that we have just taken it off a longer list, so
-	 * we assign bio_list to a pointer to the bio_list_on_stack,
-	 * thus initialising the bio_list of new bios to be
-	 * added.  ->submit_bio() may indeed add some more bios
-	 * through a recursive call to submit_bio_noacct.  If it
-	 * did, we find a non-NULL value in bio_list and re-enter the loop
-	 * from the top.  In this case we really did just take the bio
-	 * of the top of the list (no pretending) and so remove it from
-	 * bio_list, and call into ->submit_bio() again.
-	 */
-	BUG_ON(bio->bi_next);
-	bio_list_init(&bio_list_on_stack[0]);
-	current->bio_list = bio_list_on_stack;
-	do {
-		struct request_queue *q = bio->bi_disk->queue;
-
-		if (likely(bio_queue_enter(bio) == 0)) {
-			struct bio_list lower, same;
-
-			/* Create a fresh bio_list for all subordinate requests */
-			bio_list_on_stack[1] = bio_list_on_stack[0];
-			bio_list_init(&bio_list_on_stack[0]);
-			ret = do_make_request(bio);
-
-			/* sort new bios into those for a lower level
-			 * and those for the same level
-			 */
-			bio_list_init(&lower);
-			bio_list_init(&same);
-			while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL)
-				if (q == bio->bi_disk->queue)
-					bio_list_add(&same, bio);
-				else
-					bio_list_add(&lower, bio);
-			/* now assemble so we handle the lowest level first */
-			bio_list_merge(&bio_list_on_stack[0], &lower);
-			bio_list_merge(&bio_list_on_stack[0], &same);
-			bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]);
-		}
-		bio = bio_list_pop(&bio_list_on_stack[0]);
-	} while (bio);
-	current->bio_list = NULL; /* deactivate */
-
-out:
-	return ret;
+	return __submit_bio_noacct(bio);
 }
 EXPORT_SYMBOL(submit_bio_noacct);
 
-- 
2.26.2


  parent reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29 19:39 rename ->make_request_fn and move it to the block_device_operations Christoph Hellwig
2020-06-29 19:39 ` [PATCH 01/20] nfblock: stop using ->queuedata Christoph Hellwig
2020-06-29 21:47   ` Geert Uytterhoeven
2020-06-29 19:39 ` [PATCH 02/20] simdisk: " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 03/20] drbd: " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 04/20] null_blk: stop using ->queuedata for bio mode Christoph Hellwig
2020-06-29 19:39 ` [PATCH 05/20] ps3vram: stop using ->queuedata Christoph Hellwig
2020-06-29 19:39 ` [PATCH 06/20] rsxx: " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 07/20] umem: " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 08/20] zram: " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 09/20] bcache: stop setting ->queuedata Christoph Hellwig
2020-06-29 19:39 ` [PATCH 10/20] dm: stop using ->queuedata Christoph Hellwig
2020-06-29 19:39 ` [PATCH 11/20] fs: remove a weird comment in submit_bh_wbc Christoph Hellwig
2020-06-30 13:54   ` Jens Axboe
2020-06-29 19:39 ` [PATCH 12/20] block: remove the request_queue argument from blk_queue_split Christoph Hellwig
2020-06-29 19:39 ` [PATCH 13/20] block: tidy up a warning in bio_check_ro Christoph Hellwig
2020-06-29 19:39 ` [PATCH 14/20] block: remove the NULL queue check in generic_make_request_checks Christoph Hellwig
2020-06-29 19:39 ` [PATCH 15/20] block: remove the nr_sectors variable " Christoph Hellwig
2020-06-29 19:39 ` [PATCH 16/20] block: move ->make_request_fn to struct block_device_operations Christoph Hellwig
2020-06-29 19:39 ` [PATCH 17/20] block: rename generic_make_request to submit_bio_noacct Christoph Hellwig
2020-06-29 19:39 ` Christoph Hellwig [this message]
2020-07-02 14:10   ` [PATCH 18/20] block: refator submit_bio_noacct Qian Cai
2020-07-02 15:14     ` Christoph Hellwig
2020-07-02 15:52       ` Naresh Kamboju
2020-07-02 15:15     ` Naresh Kamboju
2020-06-29 19:39 ` [PATCH 19/20] block: shortcut __submit_bio_noacct for blk-mq drivers Christoph Hellwig
2020-06-29 19:39 ` [PATCH 20/20] block: remove direct_make_request Christoph Hellwig
2020-06-30 13:57 ` rename ->make_request_fn and move it to the block_device_operations Jens Axboe
2020-06-30 15:43   ` Jens Axboe
2020-06-30 18:19     ` Christoph Hellwig
2020-06-30 18:21       ` Jens Axboe
2020-07-01  8:59 rename ->make_request_fn and move it to the block_device_operations v2 Christoph Hellwig
2020-07-01  8:59 ` [PATCH 18/20] block: refator submit_bio_noacct Christoph Hellwig

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