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>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, Kiryl Shutsemau <kas@kernel.org>
Subject: Re: [PATCH 2/2] mm/truncate: Unmap large folio on split failure
Date: Tue, 21 Oct 2025 11:44:28 +0200 [thread overview]
Message-ID: <a013f044-1dc6-4c2c-9d9a-99f223157c69@redhat.com> (raw)
In-Reply-To: <20251021063509.1101728-2-kirill@shutemov.name>
On 21.10.25 08:35, 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.
Was the discussion on the old patch set already done? I can spot that
you send this series 20min after asking Christoph a question in reply to
pushback.
--
Cheers
David / dhildenb
next prev parent reply other threads:[~2025-10-21 9:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-21 6:35 [PATCH 1/2] mm/memory: Do not populate page table entries beyond i_size Kiryl Shutsemau
2025-10-21 6:35 ` [PATCH 2/2] mm/truncate: Unmap large folio on split failure Kiryl Shutsemau
2025-10-21 9:44 ` David Hildenbrand [this message]
2025-10-21 9:47 ` David Hildenbrand
2025-10-21 11:31 ` Kiryl Shutsemau
2025-10-21 11:54 ` David Hildenbrand
2025-10-21 12:25 ` Kiryl Shutsemau
2025-10-21 12:33 ` David Hildenbrand
2025-10-21 12:58 ` Kiryl Shutsemau
2025-10-21 12:08 ` [PATCH 1/2] mm/memory: Do not populate page table entries beyond i_size David Hildenbrand
2025-10-21 12:28 ` Kiryl Shutsemau
-- strict thread matches above, loose matches on Subject: below --
2025-10-20 16:30 [RFC, PATCH 0/2] Large folios vs. SIGBUS semantics Kiryl Shutsemau
2025-10-20 16:30 ` [PATCH 2/2] mm/truncate: Unmap large folio on split failure Kiryl Shutsemau
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