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b=D26D8gOgBYtI9taH8eQ4kzyi2d8YxkZt8dSUwKgAIsKyai5Pvavyf/lTEVNg0+rSx qXAiAuDFxir6oTPrOR+KcHn93C4TOIONsOi6a9mfJaFjrtAXVoEHVVpTDpDfwaCinp zB6ialuk5Pk2obvLcr9QSOS73hKuFBvypa2DqZMU= Date: Tue, 7 Apr 2026 14:42:59 -0700 From: Andrew Morton To: "Lorenzo Stoakes (Oracle)" Cc: Nico Pache , "David Hildenbrand (Arm)" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, aarcange@redhat.com, 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 Subject: Re: [PATCH mm-unstable v4 5/5] mm/khugepaged: unify khugepaged and madv_collapse with collapse_single_pmd() Message-Id: <20260407144259.011a26666eff9c96d74e39a2@linux-foundation.org> In-Reply-To: References: <7760c811-e100-4d40-9217-0813c28314be@lucifer.local> <0223d45b-e8b4-49a7-882b-477250d0c14d@kernel.org> <26fcec86-ee78-4f5c-8ca5-0e6230699cfd@kernel.org> <440d6b8a-d299-43eb-83b5-6625f9468e5e@lucifer.local> <37132e09-9c03-4afc-bc73-4bca416c5343@kernel.org> <9d5a4703-a15e-4be6-926b-af2d98db40c0@kernel.org> <87b83f7b-f0b1-4184-93a0-3b4b574c813b@lucifer.local> <20260401133145.90b094a7b87bdceb0013b5af@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; 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I added this to mm-stable a couple of days ago as 5a62019807da ("mm/khugepaged: fix issue with tracking lock"), below. It does have the Fixes: so I think we're good. commit 5a62019807da4a7add0717c962ac83b23dd12b2c Author: Lorenzo Stoakes (Oracle) Date: Tue Mar 31 13:11:18 2026 +0100 mm/khugepaged: fix issue with tracking lock =20 We are incorrectly treating lock_dropped to track both whether the lock= is currently held and whether or not the lock was ever dropped. =20 Update this change to account for this. =20 Link: https://lkml.kernel.org/r/7760c811-e100-4d40-9217-0813c28314be@lu= cifer.local Fixes: 330f3758a3bc ("mm/khugepaged: unify khugepaged and madv_collapse= with collapse_single_pmd()") Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Lance Yang Reviewed-by: Nico Pache Cc: Alistair Popple Cc: Andrea Arcangeli Cc: Anshuman Khandual Cc: Baolin Wang Cc: Barry Song Cc: Brendan Jackman Cc: Byungchul Park Cc: Catalin Marinas Cc: David Hildenbrand Cc: David Rientjes Cc: Dev Jain Cc: Gregory Price Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Kefeng Wang Cc: Liam Howlett Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Nanyong Sun Cc: Pedro Falcato Cc: Peter Xu Cc: Rafael Aquini Cc: Rakie Kim Cc: Randy Dunlap Cc: Ryan Roberts Cc: Shivank Garg Cc: Steven Rostedt Cc: Suren Baghdasaryan Cc: Takashi Iwai (SUSE) Cc: Thomas Hellstr=F6m Cc: Usama Arif Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Wei Yang Cc: Will Deacon Cc: Yang Shi Cc: Zach O'Keefe Cc: Zi Yan Signed-off-by: Andrew Morton 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, unsi= gned long start, unsigned long hstart, hend, addr; enum scan_result last_fail =3D SCAN_FAIL; int thps =3D 0; + bool mmap_unlocked =3D false; =20 BUG_ON(vma->vm_start > start); BUG_ON(vma->vm_end < end); @@ -2850,10 +2851,11 @@ int madvise_collapse(struct vm_area_struct *vma, un= signed long start, for (addr =3D hstart; addr < hend; addr +=3D HPAGE_PMD_SIZE) { enum scan_result result =3D SCAN_FAIL; =20 - if (*lock_dropped) { + if (mmap_unlocked) { cond_resched(); mmap_read_lock(mm); - *lock_dropped =3D false; + mmap_unlocked =3D false; + *lock_dropped =3D true; result =3D hugepage_vma_revalidate(mm, addr, false, &vma, cc); if (result !=3D SCAN_SUCCEED) { @@ -2864,7 +2866,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsi= gned long start, hend =3D min(hend, vma->vm_end & HPAGE_PMD_MASK); } =20 - result =3D collapse_single_pmd(addr, vma, lock_dropped, cc); + result =3D collapse_single_pmd(addr, vma, &mmap_unlocked, cc); =20 switch (result) { case SCAN_SUCCEED: @@ -2893,8 +2895,10 @@ int madvise_collapse(struct vm_area_struct *vma, uns= igned long start, =20 out_maybelock: /* Caller expects us to hold mmap_lock on return */ - if (*lock_dropped) + if (mmap_unlocked) { + *lock_dropped =3D true; mmap_read_lock(mm); + } out_nolock: mmap_assert_locked(mm); mmdrop(mm);