From: David Hildenbrand <david@redhat.com>
To: Kiryl Shutsemau <kirill@shutemov.name>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@suse.cz>, Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>, Rik van Riel <riel@surriel.com>,
Harry Yoo <harry.yoo@oracle.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeel.butt@linux.dev>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
"Darrick J. Wong" <djwong@kernel.org>,
Dave Chinner <david@fromorbit.com>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Kiryl Shutsemau <kas@kernel.org>
Subject: Re: [PATCHv2 2/2] mm/truncate: Unmap large folio on split failure
Date: Fri, 24 Oct 2025 17:43:36 +0200 [thread overview]
Message-ID: <d186391f-90f9-4fae-a986-6a12ef393c38@redhat.com> (raw)
In-Reply-To: <20251023093251.54146-3-kirill@shutemov.name>
On 23.10.25 11:32, Kiryl Shutsemau wrote:
> From: Kiryl Shutsemau <kas@kernel.org>
>
> Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are
> supposed to generate SIGBUS.
>
> This behavior might not be respected on truncation.
>
> During truncation, the kernel splits a large folio in order to reclaim
> memory. As a side effect, it unmaps the folio and destroys PMD mappings
> of the folio. The folio will be refaulted as PTEs and SIGBUS semantics
> are preserved.
>
> However, if the split fails, PMD mappings are preserved and the user
> will not receive SIGBUS on any accesses within the PMD.
>
> Unmap the folio on split failure. It will lead to refault as PTEs and
> preserve SIGBUS semantics.
>
> Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
> ---
Thanks!
Acked-by: David Hildenbrand <david@redhat.com>
--
Cheers
David / dhildenb
next prev parent reply other threads:[~2025-10-24 15:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-23 9:32 [PATCHv2 0/2] Fix SIGBUS semantics with large folios Kiryl Shutsemau
2025-10-23 9:32 ` [PATCHv2 1/2] mm/memory: Do not populate page table entries beyond i_size Kiryl Shutsemau
2025-10-23 20:49 ` Andrew Morton
2025-10-23 20:54 ` David Hildenbrand
2025-10-23 21:36 ` Andrew Morton
2025-10-24 9:26 ` Kiryl Shutsemau
2025-10-26 4:54 ` Andrew Morton
2025-10-24 15:42 ` David Hildenbrand
2025-10-24 19:32 ` Kirill A. Shutemov
2025-10-27 9:34 ` David Hildenbrand
2025-10-27 8:20 ` Hugh Dickins
2025-10-27 9:14 ` Kiryl Shutsemau
2025-10-27 9:22 ` David Hildenbrand
2025-10-29 8:31 ` Hugh Dickins
2025-10-29 10:11 ` Kiryl Shutsemau
2025-10-30 5:59 ` Hugh Dickins
2025-10-30 17:08 ` Kiryl Shutsemau
2025-10-23 9:32 ` [PATCHv2 2/2] mm/truncate: Unmap large folio on split failure Kiryl Shutsemau
2025-10-23 20:56 ` Andrew Morton
2025-10-24 9:05 ` Kiryl Shutsemau
2025-10-24 15:43 ` David Hildenbrand [this message]
2025-10-27 10:10 ` Hugh Dickins
2025-10-27 10:38 ` David Hildenbrand
2025-10-27 10:40 ` Kiryl Shutsemau
2025-10-29 9:12 ` Hugh Dickins
2025-10-29 10:21 ` Kiryl Shutsemau
2025-10-29 15:19 ` Darrick J. Wong
2025-10-29 17:10 ` Kiryl Shutsemau
2025-10-23 17:47 ` [PATCHv2 0/2] Fix SIGBUS semantics with large folios Darrick J. Wong
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