linux-kernel - Re: [f2fs-dev] [PATCH V3 4/6] nvmet: ignore discard return value

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Message-ID: <e40cb47c-9f92-4982-bf3f-45ec9f2a1681@gmail.com>
Date: Wed, 26 Nov 2025 18:14:32 +0800
From: Yongpeng Yang <yangyongpeng.storage@...il.com>
To: Chaitanya Kulkarni <ckulkarnilinux@...il.com>, axboe@...nel.dk,
 agk@...hat.com, snitzer@...nel.org, mpatocka@...hat.com, song@...nel.org,
 yukuai@...as.com, hch@....de, sagi@...mberg.me, kch@...dia.com,
 jaegeuk@...nel.org, chao@...nel.org, cem@...nel.org
Cc: dm-devel@...ts.linux.dev, linux-raid@...r.kernel.org,
 "Martin K . Petersen" <martin.petersen@...cle.com>,
 Johannes Thumshirn <johannes.thumshirn@....com>,
 linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
 linux-f2fs-devel@...ts.sourceforge.net, linux-block@...r.kernel.org,
 bpf@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [f2fs-dev] [PATCH V3 4/6] nvmet: ignore discard return value

On 11/25/25 07:48, Chaitanya Kulkarni wrote:
> __blkdev_issue_discard() always returns 0, making the error checking
> in nvmet_bdev_discard_range() dead code.
> 
> Kill the function nvmet_bdev_discard_range() and call
> __blkdev_issue_discard() directly from nvmet_bdev_execute_discard(),
> since no error handling is needed anymore for __blkdev_issue_discard()
> call.
> 
> Reviewed-by: Martin K. Petersen <martin.petersen@...cle.com>
> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Chaitanya Kulkarni <ckulkarnilinux@...il.com>
> ---
>   drivers/nvme/target/io-cmd-bdev.c | 28 +++++++---------------------
>   1 file changed, 7 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
> index 8d246b8ca604..ca7731048940 100644
> --- a/drivers/nvme/target/io-cmd-bdev.c
> +++ b/drivers/nvme/target/io-cmd-bdev.c
> @@ -362,29 +362,14 @@ u16 nvmet_bdev_flush(struct nvmet_req *req)
>   	return 0;
>   }
>   
> -static u16 nvmet_bdev_discard_range(struct nvmet_req *req,
> -		struct nvme_dsm_range *range, struct bio **bio)
> -{
> -	struct nvmet_ns *ns = req->ns;
> -	int ret;
> -
> -	ret = __blkdev_issue_discard(ns->bdev,
> -			nvmet_lba_to_sect(ns, range->slba),
> -			le32_to_cpu(range->nlb) << (ns->blksize_shift - 9),
> -			GFP_KERNEL, bio);
> -	if (ret && ret != -EOPNOTSUPP) {
> -		req->error_slba = le64_to_cpu(range->slba);
> -		return errno_to_nvme_status(req, ret);
> -	}
> -	return NVME_SC_SUCCESS;
> -}
> -
>   static void nvmet_bdev_execute_discard(struct nvmet_req *req)
>   {
> +	struct nvmet_ns *ns = req->ns;
>   	struct nvme_dsm_range range;
>   	struct bio *bio = NULL;
> +	sector_t nr_sects;
>   	int i;
> -	u16 status;
> +	u16 status = NVME_SC_SUCCESS;
>   
>   	for (i = 0; i <= le32_to_cpu(req->cmd->dsm.nr); i++) {
>   		status = nvmet_copy_from_sgl(req, i * sizeof(range), &range,
> @@ -392,9 +377,10 @@ static void nvmet_bdev_execute_discard(struct nvmet_req *req)
>   		if (status)
>   			break;
>   
> -		status = nvmet_bdev_discard_range(req, &range, &bio);
> -		if (status)
> -			break;
> +		nr_sects = le32_to_cpu(range.nlb) << (ns->blksize_shift - 9);
> +		__blkdev_issue_discard(ns->bdev,
> +				nvmet_lba_to_sect(ns, range.slba), nr_sects,
> +				GFP_KERNEL, &bio);

We also need to check for memory allocation errors in
__blkdev_issue_discard(). However, this cannot be done by simply
checking if bio is NULL. Similar to the issue with xfs_discard_extents,
once __blkdev_issue_discard()->blk_alloc_discard_bio() succeeds once,
any subsequent memory allocation failures cannot be detected by checking
if bio is NULL.

Yongpeng,

>   	}
>   
>   	if (bio) {