From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9E1BC3876D3 for ; Fri, 1 May 2026 10:41:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777632074; cv=none; b=TDeosBegDK7y1HabAA5sLQt/PV1ytQ/5PtMt6cBpYj0Cd8WZzlWi0wubxccbThXLapjU9EG8aU1gOHf4X/4YgXN/LdLwmdl6CbC2V5yECk/r4biaKbG66ii4Gpl1OUuNWfsSLvwtYINwoHVB9XVpNHv07zvhh8N7JastWv1xUNw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777632074; c=relaxed/simple; bh=/l5iTo71MJBR+aBi3Ju86nzZYKybU7sUXPkvn6urlYA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tFu5tV4LJDO42e76gPk1+mY/RHFf5GTsK9UcF46HlzT10pDdUSLgjyNep4i1jC6AzIXNcKzu3vdeEpib3GUNFKLSlTtiYwuCH/2kTlKEJeSE/oq8BsAWRGr0d9p5BCe6rd4CHn/H7TR8Mkvjb1X7zJ1p5Y9bs7v6iUpTezdn4Lg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=dK8huKGP; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="dK8huKGP" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A06AF176B; Fri, 1 May 2026 03:41:00 -0700 (PDT) Received: from [10.164.11.2] (unknown [10.164.11.2]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D86783F7B4; Fri, 1 May 2026 03:41:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1777632066; bh=/l5iTo71MJBR+aBi3Ju86nzZYKybU7sUXPkvn6urlYA=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=dK8huKGPMBqdQfhZpl3EVu3JypzYlWsSoY2FRosjQ+8l2RCK5BbdsqBgJeCNSut6C oEE00PbrwzvN+wQ/+SdSrGYhVDqJZTnsVgr4rcuZnQ8lrWXA4uvFf+yyShS2sRpCKD x1VwsJ7WgomrM0Si/wbkHNPW9nFL5C55EomYnZqQ= Message-ID: Date: Fri, 1 May 2026 16:10:58 +0530 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/khugepaged: clear MMF_VM_HUGEPAGE on mm_slot_alloc() failure To: Ye Liu , Andrew Morton , David Hildenbrand , Lorenzo Stoakes Cc: Ye Liu , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260501075708.327217-1-ye.liu@linux.dev> Content-Language: en-US From: Dev Jain In-Reply-To: <20260501075708.327217-1-ye.liu@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 01/05/26 1:27 pm, Ye Liu wrote: > From: Ye Liu > > __khugepaged_enter() sets MMF_VM_HUGEPAGE before allocating the > corresponding mm_slot. If mm_slot_alloc() fails, the function > returns with the flag set but without inserting the mm into the > khugepaged tracking structures. > > This leaves the mm in an inconsistent state: it is marked as > registered (MMF_VM_HUGEPAGE set), but will never be scanned by > khugepaged. Future attempts to register the mm are skipped since > khugepaged_enter_vma() checks the flag and returns early. > > Fix this by clearing MMF_VM_HUGEPAGE when mm_slot_alloc() fails, > restoring the ability to retry registration later. > > Signed-off-by: Ye Liu > --- > mm/khugepaged.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 7d48d4fbd5f3..60ab7c1b61dd 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -559,8 +559,10 @@ void __khugepaged_enter(struct mm_struct *mm) > return; > > slot = mm_slot_alloc(mm_slot_cache); > - if (!slot) > + if (!slot) { > + mm_flags_clear(MMF_VM_HUGEPAGE, mm); > return; > + } You could just move the test_and_set() after this no? So if slot allocation fails then MMF_VM_HUGEPAGE is never set. Fixes tag is probably required but not sure about Ccing stable. > > spin_lock(&khugepaged_mm_lock); > mm_slot_insert(mm_slots_hash, mm, slot);