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Date: Mon, 31 Aug 2026 17:12:05 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Sarthak Sharma <sarthak.sharma@arm.com>
Cc: David Hildenbrand <david@kernel.org>, Jason Gunthorpe <jgg@ziepe.ca>,
 John Hubbard <jhubbard@nvidia.com>, Peter Xu <peterx@redhat.com>, Kiryl
 Shutsemau <kas@kernel.org>, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm/gup_test: report actual pinned bytes
Message-Id: <20260831171205.9463e83d82da2a0b403da26a@linux-foundation.org>
In-Reply-To: <20260831101304.162867-1-sarthak.sharma@arm.com>
References: <20260831101304.162867-1-sarthak.sharma@arm.com>
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On Mon, 31 Aug 2026 15:43:04 +0530 Sarthak Sharma <sarthak.sharma@arm.com> wrote:

> __gup_test_ioctl() advances addr to the end of the current batch before
> checking if GUP pinned the entire requested batch. If GUP pins more than
> 0 pages but less than the requested batch size, addr still advances by
> the requested batch size.
> 
> The next iteration detects the partial pinning and breaks out of the loop.
> Again gup->size is calculated using addr - gup->addr, so it also includes
> the unpinned pages of the requested batch.
> 
> Calculate gup->size using the actual number of pages pinned multiplied
> by PAGE_SIZE.

Thanks.  Sashiko might have found a somewhat-related overflow on
32-bit.  Maybe fix that while we're in there?

	https://sashiko.dev/#/patchset/20260831101304.162867-1-sarthak.sharma@arm.com