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SubjectRe: [PATCH RFC] loop: make partition scanning reliable
Hello, David.

On Mon, Jan 26, 2015 at 11:15:19AM +0100, David Herrmann wrote:
> -static int blkdev_reread_part(struct block_device *bdev)
> +int blkdev_reread_part(struct block_device *bdev, int skipbusy)
> {
> struct gendisk *disk = bdev->bd_disk;
> int res;
> @@ -159,12 +159,15 @@ static int blkdev_reread_part(struct block_device *bdev)
> return -EINVAL;
> if (!capable(CAP_SYS_ADMIN))
> return -EACCES;
> - if (!mutex_trylock(&bdev->bd_mutex))
> + if (!skipbusy)
> + mutex_lock(&bdev->bd_mutex);
> + else if (!mutex_trylock(&bdev->bd_mutex))
> return -EBUSY;

Do we actually need the mutex_trylock() path? Why can't we just
always grab the mutex?

...
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 6cb1beb..4047985 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -637,7 +637,7 @@ out:
> * new backing store is the same size and type as the old backing store.
> */
> static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
> - unsigned int arg)
> + unsigned int arg, int *rrpart)

bool *rrpart would be better but can't we communicate this through the
return value? Wouldn't that be prettier?

Thanks.

--
tejun


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