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Date: Mon, 30 Oct 2023 15:25:11 -0600
From: Keith Busch <kbusch@kernel.org>
To: Kanchan Joshi <joshi.k@samsung.com>
Cc: Keith Busch <kbusch@meta.com>, linux-block@vger.kernel.org,
	linux-nvme@lists.infradead.org, io-uring@vger.kernel.org,
	axboe@kernel.dk, hch@lst.de, martin.petersen@oracle.com
Subject: Re: [PATCHv2 1/4] block: bio-integrity: directly map user buffers
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References: <20231027181929.2589937-1-kbusch@meta.com>
 <CGME20231027182017epcas5p1fb1f91bc876d9bc1b1229c012bcd1ea2@epcas5p1.samsung.com>
 <20231027181929.2589937-2-kbusch@meta.com>
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On Tue, Oct 31, 2023 at 02:32:48AM +0530, Kanchan Joshi wrote:
> On 10/27/2023 11:49 PM, Keith Busch wrote:
> > +
> > +	bip_for_each_vec(bv, bip, iter) {
> > +		if (dirty && !PageCompound(bv.bv_page))
> > +			set_page_dirty_lock(bv.bv_page);
> > +		unpin_user_page(bv.bv_page);
> > +	}
> > +}
> 
> Leak here, page-unpinning loop will not execute for the common (i.e., 
> no-copy) case...
> 
> > +	bip = bio_integrity_alloc(bio, GFP_KERNEL, folios);
> > +	if (IS_ERR(bip)) {
> > +		ret = PTR_ERR(bip);
> > +		goto release_pages;
> > +	}
> > +
> > +	memcpy(bip->bip_vec, bvec, folios * sizeof(*bvec));
> 
> Because with this way of copying, bip->bip_iter.bi_size will remain zero.

Good catch.
 
> Second, is it fine not to have those virt-alignment checks that are done 
> by bvec_gap_to_prev() when the pages are added using 
> bio_integrity_add_page()?

We're mapping a single user buffer. It's guaranteed to be virtually
congiguous, so no gaps.