linux-kernel - Re: [RFC PATCH v3 1/2] block: add simple copy support

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Message-ID: <SN4PR0401MB359867B95139ACD1ACFF0E709BCA0@SN4PR0401MB3598.namprd04.prod.outlook.com>
Date:   Fri, 11 Dec 2020 16:25:57 +0000
From:   Johannes Thumshirn <Johannes.Thumshirn@....com>
To:     SelvaKumar S <selvakuma.s1@...sung.com>,
        "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>
CC:     "kbusch@...nel.org" <kbusch@...nel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        Damien Le Moal <Damien.LeMoal@....com>,
        "hch@....de" <hch@....de>, "sagi@...mberg.me" <sagi@...mberg.me>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "mpatocka@...hat.com" <mpatocka@...hat.com>,
        "hare@...e.de" <hare@...e.de>,
        "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "snitzer@...hat.com" <snitzer@...hat.com>,
        "selvajove@...il.com" <selvajove@...il.com>,
        "nj.shetty@...sung.com" <nj.shetty@...sung.com>,
        "joshi.k@...sung.com" <joshi.k@...sung.com>,
        "javier.gonz@...sung.com" <javier.gonz@...sung.com>
Subject: Re: [RFC PATCH v3 1/2] block: add simple copy support

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.