Re: [PATCH v2 1/2] block: introduce new field flags in block_device

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Hi,

在 2023/11/21 17:33, Ming Lei 写道:
On Tue, Nov 21, 2023 at 07:19:26PM +0800, Yu Kuai wrote:
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 flags and replace
swithes to a bit, there are no functional changes, and preare to add
a new switch in the next patch.

In order to keep flags in the first cacheline, define it as u32 and 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 fc8d28d77495..6b420cbd4f3d 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -408,10 +408,10 @@ 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);
@@ -612,7 +612,7 @@ 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)
@@ -625,7 +625,7 @@ 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);
  	}
  }
@@ -878,9 +878,10 @@ struct bdev_handle *bdev_open_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 52e264d5a830..f7a7965eeb25 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 int		bd_flags;
  	u8			bd_partno;
-	bool			bd_write_holder;
-	bool			bd_has_submit_bio;
   dev_t                   bd_dev;
   atomic_t                bd_openers;
   spinlock_t              bd_size_lock; /* for bd_inode->i_size updates */

As I mentioned, you can convert the above/original 4 fields into single
'unsigned int', otherwise one extra 'int' filed is added. Then, 'bd_size_lock'
is moved to the 2nd cache line, which isn't big deal since the field isn't
touched in fast path. Anyway, it can be one future cleanup, so:

Thanks for the explanation, if you don't mind, I can change bd_flags to
unsigned short to keep this behaviour in the next version.

Thanks,
Kuai

Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>

Thanks,
Ming


.






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