From: Jens Axboe <axboe@kernel.dk>
Date: Mon, 18 Oct 2021 11:39:45 -0600
Subject: [PATCH] block: cache inode size in bdev
Git-commit: f09313c57a17683cbcb305989daf1d94b49fd32c
Patch-mainline: v5.16-rc1
References: jsc#PED-1183

Reading the inode size brings in a new cacheline for IO submit, and
it's in the hot path being checked for every single IO. When doing
millions of IOs per core per second, this is noticeable overhead.

Cache the nr_sectors in the bdev itself.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/genhd.c             | 1 +
 block/partitions/core.c   | 1 +
 include/linux/blk_types.h | 1 +
 include/linux/genhd.h     | 8 ++++----
 4 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 759bc06810f8..53495e3391e3 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -58,6 +58,7 @@ void set_capacity(struct gendisk *disk, sector_t sectors)
 
 	spin_lock(&bdev->bd_size_lock);
 	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
+	bdev->bd_nr_sectors = sectors;
 	spin_unlock(&bdev->bd_size_lock);
 }
 EXPORT_SYMBOL(set_capacity);
diff --git a/block/partitions/core.c b/block/partitions/core.c
index 9dbddc355b40..66ef9bc6d6a1 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -91,6 +91,7 @@ static void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
 {
 	spin_lock(&bdev->bd_size_lock);
 	i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
+	bdev->bd_nr_sectors = sectors;
 	spin_unlock(&bdev->bd_size_lock);
 }
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 472e55e0e94f..fe065c394fff 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -39,6 +39,7 @@ struct bio_crypt_ctx;
 
 struct block_device {
 	sector_t		bd_start_sect;
+	sector_t		bd_nr_sectors;
 	struct disk_stats __percpu *bd_stats;
 	unsigned long		bd_stamp;
 	bool			bd_read_only;	/* read-only policy */
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 7b0326661a1e..900325aa5d31 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -236,14 +236,14 @@ static inline sector_t get_start_sect(struct block_device *bdev)
 	return bdev->bd_start_sect;
 }
 
-static inline loff_t bdev_nr_bytes(struct block_device *bdev)
+static inline sector_t bdev_nr_sectors(struct block_device *bdev)
 {
-	return i_size_read(bdev->bd_inode);
+	return bdev->bd_nr_sectors;
 }
 
-static inline sector_t bdev_nr_sectors(struct block_device *bdev)
+static inline loff_t bdev_nr_bytes(struct block_device *bdev)
 {
-	return bdev_nr_bytes(bdev) >> SECTOR_SHIFT;
+	return bdev_nr_sectors(bdev) << SECTOR_SHIFT;
 }
 
 static inline sector_t get_capacity(struct gendisk *disk)
-- 
2.35.3