[PATCH v3 2/3] block: introduce new field bd_flags in block_device

From: Yu Kuai
Date: Tue Nov 21 2023 - 21:37:27 EST

From: Yu Kuai <yukuai3@xxxxxxxxxx>

There are multiple switches in struct block_device, use separate bool
fields for them is not gracefully. Add a new field bd_flags and replace
swithes to a bit, there are no functional changes, and prepare to add
a new switch in the next patch. In order to keep bd_flags in the first
cacheline and prevent layout to be affected, define it as u16.

Also add new helpers to set/clear/test each bit like 'bio->bi_flags'.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/bdev.c | 15 ++++++++-------
block/blk-core.c | 7 ++++---
block/genhd.c | 15 +++++++++++----
block/ioctl.c | 6 +++++-
include/linux/blk_types.h | 27 +++++++++++++++++++++------
include/linux/blkdev.h | 5 +++--
6 files changed, 52 insertions(+), 23 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index e4cfb7adb645..10f524a7416c 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -402,10 +402,10 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
bdev->bd_partno = partno;
bdev->bd_inode = inode;
bdev->bd_queue = disk->queue;
- if (partno)
- bdev->bd_has_submit_bio = disk->part0->bd_has_submit_bio;
+ if (partno && bdev_flagged(disk->part0, BD_FLAG_HAS_SUBMIT_BIO))
+ bdev_set_flag(bdev, BD_FLAG_HAS_SUBMIT_BIO);
else
- bdev->bd_has_submit_bio = false;
+ bdev_clear_flag(bdev, BD_FLAG_HAS_SUBMIT_BIO);
bdev->bd_stats = alloc_percpu(struct disk_stats);
if (!bdev->bd_stats) {
iput(inode);
@@ -606,7 +606,7 @@ static void bd_end_claim(struct block_device *bdev, void *holder)
bdev->bd_holder = NULL;
bdev->bd_holder_ops = NULL;
mutex_unlock(&bdev->bd_holder_lock);
- if (bdev->bd_write_holder)
+ if (bdev_flagged(bdev, BD_FLAG_WRITE_HOLDER))
unblock = true;
}
if (!whole->bd_holders)
@@ -619,7 +619,7 @@ static void bd_end_claim(struct block_device *bdev, void *holder)
*/
if (unblock) {
disk_unblock_events(bdev->bd_disk);
- bdev->bd_write_holder = false;
+ bdev_clear_flag(bdev, BD_FLAG_WRITE_HOLDER);
}
}

@@ -805,9 +805,10 @@ struct block_device *blkdev_get_by_dev(dev_t dev, blk_mode_t mode, void *holder,
* writeable reference is too fragile given the way @mode is
* used in blkdev_get/put().
*/
- if ((mode & BLK_OPEN_WRITE) && !bdev->bd_write_holder &&
+ if ((mode & BLK_OPEN_WRITE) &&
+ !bdev_flagged(bdev, BD_FLAG_WRITE_HOLDER) &&
(disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
- bdev->bd_write_holder = true;
+ bdev_set_flag(bdev, BD_FLAG_WRITE_HOLDER);
unblock_events = false;
}
}
diff --git a/block/blk-core.c b/block/blk-core.c
index fdf25b8d6e78..f9f8b12ba626 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -482,7 +482,8 @@ __setup("fail_make_request=", setup_fail_make_request);

bool should_fail_request(struct block_device *part, unsigned int bytes)
{
- return part->bd_make_it_fail && should_fail(&fail_make_request, bytes);
+ return bdev_flagged(part, BD_FLAG_MAKE_IT_FAIL) &&
+ should_fail(&fail_make_request, bytes);
}

static int __init fail_make_request_debugfs(void)
@@ -595,7 +596,7 @@ static void __submit_bio(struct bio *bio)
if (unlikely(!blk_crypto_bio_prep(&bio)))
return;

- if (!bio->bi_bdev->bd_has_submit_bio) {
+ if (!bdev_flagged(bio->bi_bdev, BD_FLAG_HAS_SUBMIT_BIO)) {
blk_mq_submit_bio(bio);
} else if (likely(bio_queue_enter(bio) == 0)) {
struct gendisk *disk = bio->bi_bdev->bd_disk;
@@ -703,7 +704,7 @@ void submit_bio_noacct_nocheck(struct bio *bio)
*/
if (current->bio_list)
bio_list_add(&current->bio_list[0], bio);
- else if (!bio->bi_bdev->bd_has_submit_bio)
+ else if (!bdev_flagged(bio->bi_bdev, BD_FLAG_HAS_SUBMIT_BIO))
__submit_bio_noacct_mq(bio);
else
__submit_bio_noacct(bio);
diff --git a/block/genhd.c b/block/genhd.c
index c9d06f72c587..57f96c0c8da0 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -413,7 +413,8 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
elevator_init_mq(disk->queue);

/* Mark bdev as having a submit_bio, if needed */
- disk->part0->bd_has_submit_bio = disk->fops->submit_bio != NULL;
+ if (disk->fops->submit_bio)
+ bdev_set_flag(disk->part0, BD_FLAG_HAS_SUBMIT_BIO);

/*
* If the driver provides an explicit major number it also must provide
@@ -1062,7 +1063,8 @@ static DEVICE_ATTR(diskseq, 0444, diskseq_show, NULL);
ssize_t part_fail_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
- return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_make_it_fail);
+ return sprintf(buf, "%d\n",
+ bdev_flagged(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL));
}

ssize_t part_fail_store(struct device *dev,
@@ -1071,8 +1073,13 @@ ssize_t part_fail_store(struct device *dev,
{
int i;

- if (count > 0 && sscanf(buf, "%d", &i) > 0)
- dev_to_bdev(dev)->bd_make_it_fail = i;
+ if (count > 0 && sscanf(buf, "%d", &i) > 0) {
+ if (!i)
+ bdev_clear_flag(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL);
+ else
+ bdev_set_flag(dev_to_bdev(dev), BD_FLAG_MAKE_IT_FAIL);
+
+ }

return count;
}
diff --git a/block/ioctl.c b/block/ioctl.c
index 4160f4e6bd5b..a64440f4c96b 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -394,7 +394,11 @@ static int blkdev_roset(struct block_device *bdev, unsigned cmd,
if (ret)
return ret;
}
- bdev->bd_read_only = n;
+
+ if (!n)
+ bdev_clear_flag(bdev, BD_FLAG_READ_ONLY);
+ else
+ bdev_set_flag(bdev, BD_FLAG_READ_ONLY);
return 0;
}

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index f7d40692dd94..de652045111b 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -37,6 +37,11 @@ struct bio_crypt_ctx;
#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
#define SECTOR_MASK (PAGE_SECTORS - 1)

+#define BD_FLAG_READ_ONLY 0 /* read-only-policy */
+#define BD_FLAG_WRITE_HOLDER 1
+#define BD_FLAG_HAS_SUBMIT_BIO 2
+#define BD_FLAG_MAKE_IT_FAIL 3
+
struct block_device {
sector_t bd_start_sect;
sector_t bd_nr_sectors;
@@ -44,10 +49,8 @@ struct block_device {
struct request_queue * bd_queue;
struct disk_stats __percpu *bd_stats;
unsigned long bd_stamp;
- bool bd_read_only; /* read-only policy */
+ unsigned short bd_flags;
u8 bd_partno;
- bool bd_write_holder;
- bool bd_has_submit_bio;
dev_t bd_dev;
struct inode *bd_inode; /* will die */

@@ -67,9 +70,6 @@ struct block_device {
struct super_block *bd_fsfreeze_sb;

struct partition_meta_info *bd_meta_info;
-#ifdef CONFIG_FAIL_MAKE_REQUEST
- bool bd_make_it_fail;
-#endif
/*
* keep this out-of-line as it's both big and not needed in the fast
* path
@@ -86,6 +86,21 @@ struct block_device {
#define bdev_kobj(_bdev) \
(&((_bdev)->bd_device.kobj))

+static inline bool bdev_flagged(struct block_device *bdev, unsigned int bit)
+{
+ return bdev->bd_flags & (1U << bit);
+}
+
+static inline void bdev_set_flag(struct block_device *bdev, unsigned int bit)
+{
+ bdev->bd_flags |= (1U << bit);
+}
+
+static inline void bdev_clear_flag(struct block_device *bdev, unsigned int bit)
+{
+ bdev->bd_flags &= ~(1U << bit);
+}
+
/*
* Block error status values. See block/blk-core:blk_errors for the details.
* Alpha cannot write a byte atomically, so we need to use 32-bit value.
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 51fa7ffdee83..fc1d55ef5107 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -741,13 +741,14 @@ void disk_uevent(struct gendisk *disk, enum kobject_action action);

static inline int get_disk_ro(struct gendisk *disk)
{
- return disk->part0->bd_read_only ||
+ return bdev_flagged(disk->part0, BD_FLAG_READ_ONLY) ||
test_bit(GD_READ_ONLY, &disk->state);
}

static inline int bdev_read_only(struct block_device *bdev)
{
- return bdev->bd_read_only || get_disk_ro(bdev->bd_disk);
+ return bdev_flagged(bdev, BD_FLAG_READ_ONLY) ||
+ get_disk_ro(bdev->bd_disk);
}

bool set_capacity_and_notify(struct gendisk *disk, sector_t size);
--
2.39.2