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block: turn bdev->bd_openers into an atomic_t

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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-03-30 07:29:07 +02:00 committed by Jens Axboe
parent dbdc1be325
commit 9acf381f3e
4 changed files with 11 additions and 11 deletions
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16
block/bdev.c
View File

@ -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) {
/*

2
block/partitions/core.c
View File

@ -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);

2
include/linux/blk_types.h
View File

@ -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;

2
include/linux/blkdev.h
View File

@ -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);
}
/*