linux-kernel - [PATCH 1/5] block: cache request queue in bdev

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Message-Id: <a3bfaecdd28956f03629d0ca5c63ebc096e1c809.1634219547.git.asml.silence@gmail.com>
Date:   Thu, 14 Oct 2021 15:03:26 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Christoph Hellwig <hch@...radead.org>, asml.silence@...il.com
Subject: [PATCH 1/5] block: cache request queue in bdev

There are tons of places where we need to get a request_queue only
having bdev, which turns into bdev->bd_disk->queue. There are probably a
hundred of such places considering inline helpers, and enough of them
are in hot paths.

Cache queue pointer in struct block_device and make use of it in
bdev_get_queue().

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 block/bdev.c              | 1 +
 block/genhd.c             | 4 +++-
 include/linux/blk_types.h | 1 +
 include/linux/blkdev.h    | 2 +-
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 567534c63f3d..30ae5b5d5f91 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -494,6 +494,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
 	bdev->bd_disk = disk;
 	bdev->bd_partno = partno;
 	bdev->bd_inode = inode;
+	bdev->bd_queue = disk->queue;
 	bdev->bd_stats = alloc_percpu(struct disk_stats);
 	if (!bdev->bd_stats) {
 		iput(inode);
diff --git a/block/genhd.c b/block/genhd.c
index 5e8aa0ab66c2..e11ee23a4401 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1244,6 +1244,9 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 	if (!disk->bdi)
 		goto out_free_disk;
 
+	/* bdev_alloc() might need the queue, set before the first call */
+	disk->queue = q;
+
 	disk->part0 = bdev_alloc(disk, 0);
 	if (!disk->part0)
 		goto out_free_bdi;
@@ -1259,7 +1262,6 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 	disk_to_dev(disk)->type = &disk_type;
 	device_initialize(disk_to_dev(disk));
 	inc_diskseq(disk);
-	disk->queue = q;
 	q->disk = disk;
 	lockdep_init_map(&disk->lockdep_map, "(bio completion)", lkclass, 0);
 #ifdef CONFIG_BLOCK_HOLDER_DEPRECATED
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 72736b4c057c..1e370929c89e 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -38,6 +38,7 @@ struct block_device {
 	u8			bd_partno;
 	spinlock_t		bd_size_lock; /* for bd_inode->i_size updates */
 	struct gendisk *	bd_disk;
+	struct request_queue *	bd_queue;
 
 	/* The counter of freeze processes */
 	int			bd_fsfreeze_count;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2a8689e949b4..d5b21fc8f49e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -574,7 +574,7 @@ int iocb_bio_iopoll(struct kiocb *kiocb, unsigned int flags);
 
 static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
 {
-	return bdev->bd_disk->queue;	/* this is never NULL */
+	return bdev->bd_queue;	/* this is never NULL */
 }
 
 /*
-- 
2.33.0