From: Kiryl Shutsemau <kirill@shutemov.name>
To: "Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>
Cc: David Hildenbrand <david@redhat.com>,
Ryan Roberts <ryan.roberts@arm.com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Baolin Wang <baolin.wang@linux.alibaba.com>,
Dev Jain <dev.jain@arm.com>, Barry Song <baohua@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Nico Pache <npache@redhat.com>, Zi Yan <ziy@nvidia.com>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
willy@infradead.org, mcgrof@kernel.org, gost.dev@samsung.com,
Pankaj Raghav <p.raghav@samsung.com>
Subject: Re: [PATCH] huge_memory: return -EINVAL in folio split functions when THP is disabled
Date: Tue, 2 Sep 2025 12:22:21 +0100 [thread overview]
Message-ID: <qh7s3j26aac3hyzgnr2ee6byjenstxhjnlwn4qxbvz2l32ohqc@qbhdxvpnuhtp> (raw)
In-Reply-To: <20250902084036.208921-1-kernel@pankajraghav.com>
On Tue, Sep 02, 2025 at 10:40:36AM +0200, Pankaj Raghav (Samsung) wrote:
> From: Pankaj Raghav <p.raghav@samsung.com>
>
> split_huge_page_to_list_[to_order](), split_huge_page() and
> try_folio_split() return 0 on success and error codes on failure.
>
> When THP is disabled, these functions return 0 indicating success even
> though an error code should be returned as it is not possible to split a
> folio when THP is disabled.
Other view is that the page is already split therefore nop.
> Make all these functions return -EINVAL to indicate failure instead of
> 0.
>
> This issue was discovered while experimenting enabling large folios
> without THP and found that returning 0 in these functions is resulting in
> undefined behavior in truncate operations. This change fixes the issue.
Could you elaborate on the undefined behaviour? I don't see it.
If you argue that this code should not be reachable on !THP config, add
WARN() there. But I don't see a value.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2025-09-02 11:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-02 8:40 Pankaj Raghav (Samsung)
2025-09-02 8:43 ` David Hildenbrand
2025-09-02 8:59 ` Pankaj Raghav
2025-09-02 9:06 ` David Hildenbrand
2025-09-02 11:22 ` Kiryl Shutsemau [this message]
2025-09-02 12:15 ` Pankaj Raghav
2025-09-02 12:32 ` Kiryl Shutsemau
2025-09-02 13:02 ` Pankaj Raghav
2025-09-02 13:21 ` Kiryl Shutsemau
2025-09-02 13:40 ` Pankaj Raghav (Samsung)
2025-09-02 13:50 ` David Hildenbrand
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=qh7s3j26aac3hyzgnr2ee6byjenstxhjnlwn4qxbvz2l32ohqc@qbhdxvpnuhtp \
--to=kirill@shutemov.name \
--cc=Liam.Howlett@oracle.com \
--cc=akpm@linux-foundation.org \
--cc=baohua@kernel.org \
--cc=baolin.wang@linux.alibaba.com \
--cc=david@redhat.com \
--cc=dev.jain@arm.com \
--cc=gost.dev@samsung.com \
--cc=kernel@pankajraghav.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lorenzo.stoakes@oracle.com \
--cc=mcgrof@kernel.org \
--cc=npache@redhat.com \
--cc=p.raghav@samsung.com \
--cc=ryan.roberts@arm.com \
--cc=willy@infradead.org \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox