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b=TkQVQASh19TdIE+kSJCQVylESD/gh9WNHjm+1ZaxFTtvW/Tm88WijUSmhVopEuP7Q P6m9W2moTIeXZcx1kzsNkFvwnT3ubCqFs19USnBKKTEJLVv16VDsR0kGy/II0S177L AcXrm4yLCQudSpD3y/RjZ86rarGElt+/x5rynEI1oUKEODe6e0HQu/odmnwT5yS67v H6CsFr+QoA7JliPDDu5IWdSAKfRyD17zHFHS/M1C8X1wMFeXs54/stDLEdaa/SFhoc gnJnjlK1S1Il7UJuIZyssypjNbnuk9h/BtAAfLphXMqayX1r9Y1Rcavw/NIH3yjJM1 Yyg6bBB8fMPxw== Message-ID: <1cdec848-4822-402d-91fb-50237488aec3@kernel.org> Date: Wed, 1 Apr 2026 09:05:39 +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: Nico Pache , Andrew Morton Cc: "Lorenzo Stoakes (Oracle)" , 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 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> <26fcec86-ee78-4f5c-8ca5-0e6230699cfd@kernel.org> <20260331143538.f41a5fef4201a7384388f31c@linux-foundation.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: u6m49q1p6qi6nqpxcphcm9pb93k1xtsa X-Rspamd-Queue-Id: 0629D1A0005 X-Rspamd-Server: rspam09 X-HE-Tag: 1775027156-285954 X-HE-Meta: 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 gpuOt2ED 19o7QGL4QsoNKTnckvAmlgrP33Wog763DkhbxDMVMOiSl/fYXOpiNKvdjFzcyvtAnhUoIHYd7wWAHq2ShCRpwTiRmLZQVSA/1g6S/2QI283SuJGCDf/z2GL0OgiqOEhQZLzlmHWRYuXDfyq34zWc4xdot66Xz8znsb3YWRd2YBCJXEthSwGZ6Bb5PtMgUtBzkiCiWg4iredNtbq4Xv5nYqP7PJtDTo+dVXdSTFBU44TLEecT6tAqYKrnDmAWaagTyh07shK8boTonULZMmcnmLjDQVev2cZ00WHp/XAk7cV6TJt0/pNWxqVkmIsHLTx3EFNpaZ/tXFvpPDyWEez3NS0ncn+shXcn5D+JCCT2o+fEYLEPG9FFPjF+uar0Elf8dHwREANuV7f/mCWXBr1xtxDk3Bp7MMemrH424Vppt6wwgS0Ms5zofIxMWS02YSkGiXAz7R3bV3LVjTdXfKnYlIS7W4mDQJzFNTNckJQveT1C+TEivlmdzsPSlMrGX6uU/Et6W43VhTCm/DeBFaUBFhQJQBA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/31/26 23:49, Nico Pache wrote: > On Tue, Mar 31, 2026 at 3:35 PM Andrew Morton wrote: >> >> On Tue, 31 Mar 2026 22:00:58 +0200 "David Hildenbrand (Arm)" wrote: >> >>> >>> Right. >>> >>> The original code used >>> >>> bool mmap_locked = true; >>> >>> If the fix get squashed, maybe we should revert to that handling to >>> minimize the churn? >>> >>> (this is not in stable, right?) >> >> "mm/khugepaged: unify khugepaged and madv_collapse with >> collapse_single_pmd(): is presently in mm-stable. >> >> Doing a big rebase&rework isn't the done thing, I believe. So queue it >> afterwards, add the Fixes: and tolerate the minor runtime bisection >> hole. It ends up looking like a later hotfix. >> >> >> Below is what I added to mm-unstable. I added a note-to-self to check >> in on Nico's question at >> https://lore.kernel.org/all/CAA1CXcCYLGQBy9nT-MSTPVK=XgWWtD6Af-QiA_6pXtM_2pybPg@mail.gmail.com/T/#u >> >> >> From: "Lorenzo Stoakes (Oracle)" >> Subject: mm/khugepaged: fix issue with tracking lock >> Date: Tue, 31 Mar 2026 13:11:18 +0100 >> >> 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. >> >> Link: https://lkml.kernel.org/r/7760c811-e100-4d40-9217-0813c28314be@lucifer.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 >> ... >> Signed-off-by: Andrew Morton >> --- >> >> mm/khugepaged.c | 12 ++++++++---- >> 1 file changed, 8 insertions(+), 4 deletions(-) >> >> --- a/mm/khugepaged.c~mm-khugepaged-fix-issue-with-tracking-lock >> +++ a/mm/khugepaged.c >> @@ -2828,6 +2828,7 @@ int madvise_collapse(struct vm_area_stru >> 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_stru >> 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_stru >> hend = min(hend, vma->vm_end & HPAGE_PMD_MASK); >> } >> >> - result = collapse_single_pmd(addr, vma, lock_dropped, cc); >> + result = collapse_single_pmd(addr, vma, &mmap_unlocked, cc); >> >> switch (result) { >> case SCAN_SUCCEED: >> @@ -2893,8 +2895,10 @@ int madvise_collapse(struct vm_area_stru >> >> out_maybelock: >> /* Caller expects us to hold mmap_lock on return */ >> - if (*lock_dropped) >> + if (mmap_unlocked) { >> + *lock_dropped = true; > > Hmm this was =false in David's example and = true here? Now i am also > confused hahaha. It seems Lorenzo's code is correct. I think i > responded to my own code changes, when I thought David was replying to > Lorenzo's. I think I messed up that in my posting when manually applying :) So this here is correct. -- Cheers, David