On Thu 24-03-22 08:51:11, Christoph Hellwig wrote:
> 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@xxxxxx>
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
BTW I suspect that drivers/block/aoe/ could now use bd_openers instead of
its driver specific mirror of it (->nopen). But that's certainly a separate
cleanup for some other time.
Honza
> ---
> block/bdev.c | 16 ++++++++--------
> block/partitions/core.c | 2 +-
> include/linux/blk_types.h | 2 +-
> include/linux/blkdev.h | 2 +-
> 4 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/block/bdev.c b/block/bdev.c
> index 13de871fa8169..7bf88e591aaf3 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -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) {
> /*
> diff --git a/block/partitions/core.c b/block/partitions/core.c
> index 2ef8dfa1e5c85..373ed748dcf26 100644
> --- a/block/partitions/core.c
> +++ b/block/partitions/core.c
> @@ -486,7 +486,7 @@ 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);
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 0c3563b45fe90..b1ced43ed0d3f 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -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;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 9824ebc9b4d31..6b7c5af1d01df 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -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);
> }
>
> /*
> --
> 2.30.2
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
