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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi,

在 2023/11/20 14:58, Ming Lei 写道:
On Mon, Nov 20, 2023 at 02:37:59PM +0800, Yu Kuai wrote:
Hi,

在 2023/11/20 11:00, Ming Lei 写道:
On Mon, Nov 20, 2023 at 05:38:46PM +0800, Yu Kuai wrote:
From: Yu Kuai <yukuai3@xxxxxxxxxx>

There are multiple switches in struct block_device, use seperate bool
fields for them is not gracefully. Add a new field flags and replace
swithes to a bit, there are no functional changes, and preapre to add
a new switch in the next patch.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
   block/bdev.c              | 15 ++++++++-------
   block/blk-core.c          |  7 ++++---
   block/genhd.c             |  8 +++++---
   block/ioctl.c             |  2 +-
   include/linux/blk_types.h | 12 ++++++------
   include/linux/blkdev.h    |  5 +++--
   6 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index fc8d28d77495..cb849bcf61ae 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 && test_bit(BD_FLAG_HAS_SUBMIT_BIO, &disk->part0->flags))
+		set_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
   	else
-		bdev->bd_has_submit_bio = false;
+		clear_bit(BD_FLAG_HAS_SUBMIT_BIO, &bdev->flags);
   	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 (test_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags))
   			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;
+		clear_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags);
   	}
   }
@@ -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) &&
+		    !test_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags) &&
   		    (disk->event_flags & DISK_EVENT_FLAG_BLOCK_ON_EXCL_WRITE)) {
-			bdev->bd_write_holder = true;
+			set_bit(BD_FLAG_WRITE_HOLDER, &bdev->flags);
   			unblock_events = false;
   		}
   	}
diff --git a/block/blk-core.c b/block/blk-core.c
index fdf25b8d6e78..577a693165d8 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 test_bit(BD_FLAG_MAKE_IT_FAIL, &part->flags) &&
+		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 (!test_bit(BD_FLAG_HAS_SUBMIT_BIO, &bio->bi_bdev->flags)) {
   		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 (!test_bit(BD_FLAG_HAS_SUBMIT_BIO, &bio->bi_bdev->flags))
   		__submit_bio_noacct_mq(bio);
   	else
   		__submit_bio_noacct(bio);
diff --git a/block/genhd.c b/block/genhd.c
index c9d06f72c587..026f4c6d5b7e 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)
+		set_bit(BD_FLAG_HAS_SUBMIT_BIO, &disk->part0->flags);
   	/*
   	 * 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",
+		       test_bit(BD_FLAG_MAKE_IT_FAIL, &dev_to_bdev(dev)->flags));
   }
   ssize_t part_fail_store(struct device *dev,
@@ -1072,7 +1074,7 @@ 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;
+		set_bit(BD_FLAG_MAKE_IT_FAIL, &dev_to_bdev(dev)->flags);
   	return count;
   }
diff --git a/block/ioctl.c b/block/ioctl.c
index 4160f4e6bd5b..a548c718a5fb 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -394,7 +394,7 @@ static int blkdev_roset(struct block_device *bdev, unsigned cmd,
   		if (ret)
   			return ret;
   	}
-	bdev->bd_read_only = n;
+	set_bit(BD_FLAG_READ_ONLY, &bdev->flags);
   	return 0;
   }
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 52e264d5a830..95bd26c62655 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -37,17 +37,20 @@ 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;
   	struct gendisk *	bd_disk;
   	struct request_queue *	bd_queue;
   	struct disk_stats __percpu *bd_stats;
+	unsigned long		flags;
   	unsigned long		bd_stamp;
-	bool			bd_read_only;	/* read-only policy */
   	u8			bd_partno;
-	bool			bd_write_holder;
-	bool			bd_has_submit_bio;

The idea looks good, but not necessary to add new 8 bytes, and you may
put all these flags and `bd_partno` into single 'unsigned long', and add
helpers to retrieve part no, since there are not many ->bd_partno
references.

Yes, it make sense.

By the way, take a look at component of block_device, I think they can
be reorganized to save some space, in this case, new 8 bytes won't make
this struct bigger, in fact, total size will be shrinked by 8 types
after following changes:

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 95bd26c62655..c94242a9ad92 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -50,7 +50,6 @@ struct block_device {
         struct disk_stats __percpu *bd_stats;
         unsigned long           flags;
         unsigned long           bd_stamp;
-       u8                      bd_partno;
         dev_t                   bd_dev;
         atomic_t                bd_openers;
         spinlock_t              bd_size_lock; /* for bd_inode->i_size
updates */
@@ -60,13 +59,14 @@ struct block_device {
         const struct blk_holder_ops *bd_holder_ops;
         struct mutex            bd_holder_lock;
         int                     bd_holders;
+       u8                      bd_partno;

'bd_partno' needs to be kept in the 1st cacheline, so not good to move
it.

Got it, and same for bd_dev and bd_openers, I'll send a new version
based on your first adivce.

Thanks,
Kuai


Thanks,
Ming


.






[Index of Archives]     [Linux RAID]     [Linux SCSI]     [Linux ATA RAID]     [IDE]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Device Mapper]

  Powered by Linux