From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 517712E54A3 for ; Tue, 14 Apr 2026 09:46:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776159999; cv=none; b=WPhc3tiSkJdaLcylT57mQ84/3bBHZ2tO92kKqXJLGqrK+bt2UU3ch5qbvmazRA6KfbwaGvp9ussOD1voN4qjMIkOa0cMRLV42RN+eYNT847WgTosBfyUXRM1OU+ZJJr1uawNgajRK0d3jnRyWLhpvq3+K19lXXQ2+drA7hBC7e8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776159999; c=relaxed/simple; bh=6sEhxOOE1Aj7pCDiLrWqUUaqum3nPTJ8S4/1FTOMZ/k=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=aTvMngFTak1K+UQgsfxW3m8lnsQKFpPvtZ+VbwM2TxOney8yWMv1WUOugMjf+IBwoMriDP5Uuh8U5vDrAw9wwDDyfhzvoqv6mSnJ5ssEPCE0gbF63hYTlQHIyIvD3EtOJa+6sqO/yohrQytWv2cC7GGaKBK2tPUMK68n9q/C2Hc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kIdLQ3ob; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kIdLQ3ob" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2C87FC2BCB4; Tue, 14 Apr 2026 09:46:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776159999; bh=6sEhxOOE1Aj7pCDiLrWqUUaqum3nPTJ8S4/1FTOMZ/k=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=kIdLQ3obujLEplnrv+jkqgccCFd1D+wekSsoKKeRVxq80FUf2iFHPBipViZo/dXW9 y1ET3yZgrUSmUaN8Bb/Qypty2L5rzXf8S68UhZgJLjqxgEUlotzWXrqV9XsrdvQWT5 FHynNmxIcfiCL9HnuUa/UCKSCVr6RMPptdukwKOl94rN0ISUMn1xrTu7CkvQ8Hom+N MNQKqJzaAhs2WZDHpV1Q+JQKAy3CZxghj04bLBcb2PkWq9g0xX1EZxZscGHZbNfRv+ w+HHVNvNG7qir8DdWuko87cWdFx/G8hJMMU1Ws792PDSQEBXlleqDsRvJn0yfFF2kV MHWV6y0Q8A81w== Message-ID: Date: Tue, 14 Apr 2026 11:46:33 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate_device: fix double unlock and remove dead code To: Matthew Brost , Sunny Patel Cc: Andrew Morton , Zi Yan , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260413130927.13263-1-nueralspacetech@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/14/26 01:30, Matthew Brost wrote: > On Mon, Apr 13, 2026 at 06:39:23PM +0530, Sunny Patel wrote: >> Fix two bugs in device migration paths: >> >> 1) migrate_vma_collect_huge_pmd() calls spin_unlock after >> softleaf_entry_wait_on_locked(), which already releases the ptl. >> >> 2) migrate_vma_insert_huge_pmd_page() has a dead else-if branch and this >> branch is always unreachable. >> >> Signed-off-by: Sunny Patel >> --- >> mm/migrate_device.c | 4 +--- >> 1 file changed, 1 insertion(+), 3 deletions(-) >> >> diff --git a/mm/migrate_device.c b/mm/migrate_device.c >> index 8079676c8f1f..0e005c26ee88 100644 >> --- a/mm/migrate_device.c >> +++ b/mm/migrate_device.c >> @@ -177,7 +177,6 @@ static int migrate_vma_collect_huge_pmd(pmd_t *pmdp, unsigned long start, >> >> if (softleaf_is_migration(entry)) { >> softleaf_entry_wait_on_locked(entry, ptl); >> - spin_unlock(ptl); >> return -EAGAIN; >> } > > This entire if statement is dead code, since we bail out and collect a > skip on !softleaf_is_device_private immediately above. I thought we > already had a patch from Davidlohr Bueso 'mm/migrate_device: remove dead > migration entry check in migrate_vma_collect_huge_pmd()' that removed > this whole if statement. I even have an email from Andrew pulling this > patch, but it looks like the code is still present in 7.0. > > I found this link via a google search which contains the above patch > too: > > https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/25-new/+/f405e7bc5d93a541cf11663b2424baf0a03b496f%5E%21/ > > Look like this change got lost somehow? Oh, even better, then we don't even need a Fixes: -- Cheers, David