Commit 9acf381f authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: turn bdev->bd_openers into an atomic_t 



All manipulation of bd_openers is under disk->open_mutex and will remain
so for the foreseeable future.  But at least one place reads it without
the lock (blkdev_get) and there are more to be added.  So make sure the
compiler does not do turn the increments and decrements into non-atomic
sequences by using an atomic_t.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-6-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent dbdc1be3

block/bdev.c

+8 −8
Original line number Diff line number Diff line
@@ -673,17 +673,17 @@ static int blkdev_get_whole(struct block_device *bdev, fmode_t mode) 
		}

	}



	if (!bdev->bd_openers)

	if (!atomic_read(&bdev->bd_openers))

		set_init_blocksize(bdev);

	if (test_bit(GD_NEED_PART_SCAN, &disk->state))

		bdev_disk_changed(disk, false);

	bdev->bd_openers++;

	atomic_inc(&bdev->bd_openers);

	return 0;

}



static void blkdev_put_whole(struct block_device *bdev, fmode_t mode)

{

	if (!--bdev->bd_openers)

	if (atomic_dec_and_test(&bdev->bd_openers))

		blkdev_flush_mapping(bdev);

	if (bdev->bd_disk->fops->release)

		bdev->bd_disk->fops->release(bdev->bd_disk, mode);
@@ -694,7 +694,7 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode) 
	struct gendisk *disk = part->bd_disk;

	int ret;



	if (part->bd_openers)

	if (atomic_read(&part->bd_openers))

		goto done;



	ret = blkdev_get_whole(bdev_whole(part), mode);
@@ -708,7 +708,7 @@ static int blkdev_get_part(struct block_device *part, fmode_t mode) 
	disk->open_partitions++;

	set_init_blocksize(part);

done:

	part->bd_openers++;

	atomic_inc(&part->bd_openers);

	return 0;



out_blkdev_put:
@@ -720,7 +720,7 @@ static void blkdev_put_part(struct block_device *part, fmode_t mode) 
{

	struct block_device *whole = bdev_whole(part);



	if (--part->bd_openers)

	if (!atomic_dec_and_test(&part->bd_openers))

		return;

	blkdev_flush_mapping(part);

	whole->bd_disk->open_partitions--;
@@ -899,7 +899,7 @@ void blkdev_put(struct block_device *bdev, fmode_t mode) 
	 * of the world and we want to avoid long (could be several minute)

	 * syncs while holding the mutex.

	 */

	if (bdev->bd_openers == 1)

	if (atomic_read(&bdev->bd_openers) == 1)

		sync_blockdev(bdev);



	mutex_lock(&disk->open_mutex);
@@ -1044,7 +1044,7 @@ void sync_bdevs(bool wait) 
		bdev = I_BDEV(inode);



		mutex_lock(&bdev->bd_disk->open_mutex);

		if (!bdev->bd_openers) {

		if (!atomic_read(&bdev->bd_openers)) {

			; /* skip */

		} else if (wait) {

			/*

block/partitions/core.c

+1 −1
Original line number Diff line number Diff line
@@ -478,7 +478,7 @@ int bdev_del_partition(struct gendisk *disk, int partno) 
		goto out_unlock;



	ret = -EBUSY;

	if (part->bd_openers)

	if (atomic_read(&part->bd_openers))

		goto out_unlock;



	delete_partition(part);

include/linux/blk_types.h

+1 −1
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ struct block_device { 
	unsigned long		bd_stamp;

	bool			bd_read_only;	/* read-only policy */

	dev_t			bd_dev;

	int			bd_openers;

	atomic_t		bd_openers;

	struct inode *		bd_inode;	/* will die */

	struct super_block *	bd_super;

	void *			bd_claiming;

include/linux/blkdev.h

+1 −1
Original line number Diff line number Diff line
@@ -188,7 +188,7 @@ static inline bool disk_live(struct gendisk *disk) 
 */

static inline unsigned int disk_openers(struct gendisk *disk)

{

	return disk->part0->bd_openers;

	return atomic_read(&disk->part0->bd_openers);

}



/*