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From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
To: David Hildenbrand <david@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Donet Tom <donettom@linux.ibm.com>
Cc: Shuah Khan <shuah@kernel.org>, Matthew Wilcox <willy@infradead.org>, Tony Battersby <tonyb@cybernetics.com>, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Mike Rapoport <rppt@kernel.org>, Muchun Song <songmuchun@bytedance.com>
Subject: Re: [PATCH] selftest: mm: Test if hugepage does not get leaked during __bio_release_pages()
In-Reply-To: <d551d1cd-a02f-42aa-9de2-10ff7757224c@redhat.com>
Date: Fri, 24 May 2024 12:23:15 +0530
Message-ID: <87msofsntw.fsf@gmail.com>
References: <20240523063905.3173-1-donettom@linux.ibm.com> <20240523121344.6a67a109e0af2ba70973b34b@linux-foundation.org> <d551d1cd-a02f-42aa-9de2-10ff7757224c@redhat.com>
Precedence: bulk


dropping stable email again.

David Hildenbrand <david@redhat.com> writes:

> On 23.05.24 21:13, Andrew Morton wrote:
>> On Thu, 23 May 2024 01:39:05 -0500 Donet Tom <donettom@linux.ibm.com> wrote:
>> 
>>> Commit 1b151e2435fc ("block: Remove special-casing of compound
>>> pages") caused a change in behaviour when releasing the pages
>>> if the buffer does not start at the beginning of the page. This
>>> was because the calculation of the number of pages to release
>>> was incorrect.
>>> This was fixed by commit 38b43539d64b ("block: Fix page refcounts
>>> for unaligned buffers in __bio_release_pages()").
>>>
>>> We pin the user buffer during direct I/O writes. If this buffer is a
>>> hugepage, bio_release_page() will unpin it and decrement all references
>>> and pin counts at ->bi_end_io. However, if any references to the hugepage
>>> remain post-I/O, the hugepage will not be freed upon unmap, leading
>>> to a memory leak.
>>>
>>> This patch verifies that a hugepage, used as a user buffer for DIO
>>> operations, is correctly freed upon unmapping, regardless of whether
>>> the offsets are aligned or unaligned w.r.t page boundary.
>>>
>> 
>
> Two SOF, is there a Co-developed-by: missing?
>

Sorry about that. Andrew, could you please add the tag (let me know if you
would like me to send v2). Will take care of it next time.

Co-developed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

-ritesh