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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774968425; bh=Ykir5ONzmHomVd+ALx+S4o3LLuSFRljRqKIFub+1lSg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=E2hZlHleGJjipODBYKXQl9jJ8ua2xERXwE4CkSZ594U5xwhzxhOx+jj76KuT1Q9Y/ ruBFE5IlBVrZXtKxeBRBYJn0DLLdthndOQ6v7N+v2Npghp+uLJyUbbj9bKSq67VEmr z5ByoQm/oWCBs+ia+K28uqu5Poj7TI8iGoRFY4/shY5gE1kUXShkOz55IzMVCMWYsc 1/3ubpogkyxRp4AcxyEzoVsG9sScT16Z+VWld1qYFDvkUuFPO8DrUy1FVwURyXkZs4 4Xn9/cLIn0ZPG6ZZ30ylOZTtWn1cTaNq+5exskDL4H3+McS98z+F3hyVGf3b6FRKmT r/Omw50/+qqAw== Message-ID: <2b2f935c-e72f-41db-81f9-3ef33139e60c@kernel.org> Date: Tue, 31 Mar 2026 16:46:50 +0200 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)" Cc: Nico Pache , 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> <0223d45b-e8b4-49a7-882b-477250d0c14d@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 9E9B2120012 X-Stat-Signature: tt8jwpnenrrbmc9yrfbnd9go936bcyk3 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1774968426-565916 X-HE-Meta: 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 P0cDgMnQ Iy3XzuUROCR7XgvUPuRZq/gknhaaWwsTWM6uMggMUkHAds0fWvQDFXWnuZDh7wX0z+DV/13o2kMGiTwac/KSDSNN0TZ1cy1OIlcYWnKXKzQw6Cd1VWVJfQnFn9ZetIewtIpiW9cWW7JlT6fSb5Vd4Eg6boaOY+2PgPQhBYKI3zuOzaMOTAqH2YAWjksGgAp3T6iXGxZ2aVx0LlEejupC+jqCl38a6ZkMhqgbXzDtoCnzMEwNWFFehyyR1EoohPFsZFiY4Cnxj/RNJvDQBOaoPQFETtuRGES3kqcAxBoe1SLgrd/jnbrhQce8Y1opbHgJ2g5Q42cYLxYhaZfCjqdSiMY3JmudZDHEo/WKbBTWVsEa6U2DfDZ3r3rhwiwABC1WqJUueKvZXAEa0xB8Al7cEBVeu6w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/31/26 16:15, Lorenzo Stoakes (Oracle) wrote: > On Tue, Mar 31, 2026 at 04:13:29PM +0200, David Hildenbrand (Arm) wrote: >>> >>> 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? Great, thanks! -- Cheers, David