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Date: Thu, 9 Nov 2023 15:35:17 +0100
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, Ed Tsai <ed.tsai@mediatek.com>
Subject: Re: [PATCH V2 1/2] block: don't call into iov_iter_revert if
 nothing is left
Message-ID: <20231109143517.GA30592@lst.de>
References: <20231109082827.2276696-1-ming.lei@redhat.com> <20231109082827.2276696-2-ming.lei@redhat.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

>  	if (bio->bi_bdev) {
>  		size_t trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
> -		iov_iter_revert(iter, trim);
> -		size -= trim;
> +
> +		if (trim) {
> +			iov_iter_revert(iter, trim);
> +			size -= trim;
> +		}

We also need to fix this.  This isn't supposed to be called without
a bdev set, but Kent broke this.  But if we don't have a bdev
we need to pass the block size manually and still do the revert if needed.