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 915883126DF for ; Tue, 31 Mar 2026 14:13:43 +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=1774966423; cv=none; b=r3vrjsOM9bJfVSCo1+NuJBhoq5hFoeHT50bNPap8lKa1N90HN/aDnRDor/c4hYllsHW/VAR08lgQSdkSw0nYTZKpZpG828kcmKBh5PAAW9cTP6X4tx1nR/2gDR3fP6sNHbiiBrah6b/Cu/eqsgoydF4DtOcNnKpGL8m2armD4QQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774966423; c=relaxed/simple; bh=GNemy5BN+CGFx1ZwGeM3VFL0of0Cf3xkUkABcfcUz64=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Wf5rtyoBogo6ZWCTw3lylcOFHiH2ocm0afvaUp5s+Lm+clk0ZRXSSZ4K1xVZCGnQ91CPBXLafQjnFfztnJC6jsDJEqwvh9k6sEBQgVCpDx3WAtILVeJ+rc3C6AOETwivTJKttNibqEiypixG92suBjTpG9LQ5s9tVDJ+0OyhNpE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CovphkuT; 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="CovphkuT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 383F1C19423; Tue, 31 Mar 2026 14:13:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774966423; bh=GNemy5BN+CGFx1ZwGeM3VFL0of0Cf3xkUkABcfcUz64=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=CovphkuT1CwVRkGB7m0PrEwmP54yl6LImh92u3SL7qbbZPA5+9tBaJYj2qnS00A5g iC+Lu3RXlI7no/6ZK0c+6sQwndKKttgEh3w0EyG8vTIAS0fucIna1Txz9CGyjwdGKK 7qwjxCsYI25TNAHCLpuYenW0kCsUdb8BQCmBxCKM6UDo2xGHdZU7NwZ6Um0banwCbh qVgDMUv3lWPneRvrf3OZapuxILlOypvkUsl85vXr81PogJPRiLEiOPi0EApbqlAl46 yef/uApqF2re7OQzIwBMtBOEfZBpQcVowtJsXLUeSIyCWg5gw8Z6LHjwXRiR8NDljc 3RrdRd0TjYydQ== Message-ID: <0223d45b-e8b4-49a7-882b-477250d0c14d@kernel.org> Date: Tue, 31 Mar 2026 16:13:29 +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-unstable v4 5/5] mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() To: "Lorenzo Stoakes (Oracle)" , Nico Pache Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260325114022.444081-1-npache@redhat.com> <20260325114022.444081-6-npache@redhat.com> <7760c811-e100-4d40-9217-0813c28314be@lucifer.local> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit >> + if (*lock_dropped) { >> cond_resched(); >> mmap_read_lock(mm); >> - mmap_locked = true; >> + *lock_dropped = false; > > So this is the bug. 'lock_dropped' needs to record if the lock was _ever_ > dropped, not if it is _currently_ dropped. Ah, well spotted. I thought we discussed that at some point during review ... Thanks for tackling this! [...] > > ----8<---- > From a4dfc7718a15035449f344a0bc7f58e449366405 Mon Sep 17 00:00:00 2001 > From: "Lorenzo Stoakes (Oracle)" > Date: Tue, 31 Mar 2026 13:11:18 +0100 > Subject: [PATCH] mm/khugepaged: fix issue with tracking lock > > We are incorrectly treating lock_dropped to track both whether the lock is > currently held and whether or not the lock was ever dropped. > > Update this change to account for this. > > Signed-off-by: Lorenzo Stoakes (Oracle) > --- > mm/khugepaged.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index d21348b85a59..b8452dbdb043 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2828,6 +2828,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, > unsigned long hstart, hend, addr; > enum scan_result last_fail = SCAN_FAIL; > int thps = 0; > + bool mmap_unlocked = false; > > BUG_ON(vma->vm_start > start); > BUG_ON(vma->vm_end < end); > @@ -2850,10 +2851,11 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, > for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) { > enum scan_result result = SCAN_FAIL; > > - if (*lock_dropped) { > + if (mmap_unlocked) { > cond_resched(); > mmap_read_lock(mm); > - *lock_dropped = false; > + mmap_unlocked = false; > + *lock_dropped = true; > result = hugepage_vma_revalidate(mm, addr, false, &vma, > cc); > if (result != SCAN_SUCCEED) { > @@ -2864,7 +2866,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, (in hurry so I might be wrong) Do we have to handle when collapse_single_pmd() dropped the lock as well? -- Cheers, David