From: sashiko-bot@kernel.org
To: "Heiko Carstens" <hca@linux.ibm.com>
Cc: "Vasily Gorbik" <gor@linux.ibm.com>,
"Alexander Gordeev" <agordeev@linux.ibm.com>,
"Christian Borntraeger" <borntraeger@linux.ibm.com>,
"Heiko Carstens" <hca@linux.ibm.com>,
linux-s390@vger.kernel.org
Subject: Re: [PATCH] s390/mm: Simplify crst_table_upgrade()
Date: Thu, 27 Aug 2026 10:37:28 +0000 [thread overview]
Message-ID: <20260827103729.080BD1F000E9@smtp.kernel.org> (raw)
In-Reply-To: <20260827102832.3823857-1-hca@linux.ibm.com>
> In case of an upgrade from four to five level page tables, and a failing
> pgd allocation, the exit path of crst_table_upgrade() would incorrectly
> dereference the p4d NULL pointer via pagetable_dtor().
>
> Address this by reworking crst_table_upgrade(), which basically is a
> revert of [1]. Take into account that GFP_KERNEL order-2 allocation
> failures are very unlikely. Therefore keep the code as simple as
> possible:
>
> In case of an upgrade from three to five levels, and an allocation
> failure of the fifth page table level, keep the upgrade to four levels
> instead of reverting back to three levels. This allows to keep error
> handling minimal.
>
> [1] commit 31932757c612 ("s390/mm: optimize page table upgrade routine")
>
> Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260827102832.3823857-1-hca@linux.ibm.com?part=1
next prev parent reply other threads:[~2026-08-27 10:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-27 10:28 [PATCH] s390/mm: Simplify crst_table_upgrade() Heiko Carstens
2026-08-27 10:37 ` sashiko-bot [this message]
2026-08-27 15:59 ` Vasily Gorbik
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