[dm-devel] [RFC PATCH v3 1/2] block: add simple copy support

[Johannes Thumshirn]

On 11/12/2020 15:57, SelvaKumar S wrote:
[...] 
> +int blk_copy_emulate(struct block_device *bdev, struct blk_copy_payload *payload,
> +		gfp_t gfp_mask)
> +{
> +	struct request_queue *q = bdev_get_queue(bdev);
> +	struct bio *bio;
> +	void *buf = NULL;
> +	int i, nr_srcs, max_range_len, ret, cur_dest, cur_size;
> +
> +	nr_srcs = payload->copy_range;
> +	max_range_len = q->limits.max_copy_range_sectors << SECTOR_SHIFT;
> +	cur_dest = payload->dest;
> +	buf = kvmalloc(max_range_len, GFP_ATOMIC);

Why GFP_ATOMIC and not the passed in gfp_mask? Especially as this is a kvmalloc()
which has the potential to grow quite big.

> +int __blkdev_issue_copy(struct block_device *bdev, sector_t dest,
> +		sector_t nr_srcs, struct range_entry *rlist, gfp_t gfp_mask,
> +		int flags, struct bio **biop)
> +{

[...]

> +	total_size = struct_size(payload, range, nr_srcs);
> +	payload = kmalloc(total_size, GFP_ATOMIC | __GFP_NOWARN);

Same here. 


> diff --git a/block/ioctl.c b/block/ioctl.c
> index 6b785181344f..a4a507d85e56 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -142,6 +142,47 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode,
>  				    GFP_KERNEL, flags);
>  }
>  
> +static int blk_ioctl_copy(struct block_device *bdev, fmode_t mode,
> +		unsigned long arg, unsigned long flags)
> +{

[...]

> +
> +	rlist = kmalloc_array(crange.nr_range, sizeof(*rlist),
> +			GFP_ATOMIC | __GFP_NOWARN);

And here. I think this one can even be GFP_KERNEL.