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Tue, 10 Nov 2026 17:31:25 -0800 (PST) Received: from [10.125.112.22] ([122.11.210.25]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b182e0ecd3sm441451a91.3.2026.11.10.17.31.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Nov 2026 17:31:24 -0800 (PST) Message-ID: Date: Wed, 11 Nov 2026 09:31:14 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/migrate: improve mlock tracking for PTE-mapped large folios From: Wandun To: david@kernel.org, hughd@google.com, akpm@linux-foundation.org Cc: ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261110123218.1579490-1-chenwandun1@gmail.com> Content-Language: en-US In-Reply-To: <20261110123218.1579490-1-chenwandun1@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/10/26 20:32, Wandun Chen wrote: > From: Wandun Chen > > Commit ab521b4142aa ("mm/rmap: improve mlock tracking for large folios") > mlocks a large folio when all its pages are added in one rmap operation. > However, when a PTE-mapped large folio is migrated, remove_migration_pte() > restores PTEs individually, passing nr_pages = 1 to the rmap helpers. As a > result, PG_mlocked is not set on the destination folio. > > Reclaim can restore mlock in try_to_unmap(), but Mlocked in /proc/meminfo > remains undercounted until that scan occurs. > > Restore mlock once the full mapping has been restored in a locked VMA > under one page table lock, rather than waiting for try_to_unmap() to > restore the mlock state. I forgot to include the v1-to-v2 changelog: Changes in v2: 1. Reword the subject and commit message. 2. Drop the Fixes tag. Best regards, Wandun > > Signed-off-by: Wandun Chen > --- > mm/migrate.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 94033c222e04..140e291d4587 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -353,6 +353,7 @@ static bool remove_migration_pte(struct folio *folio, > { > struct rmap_walk_arg *rmap_walk_arg = arg; > DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION); > + unsigned long nr_ptes = 0; > > while (page_vma_mapped_walk(&pvmw)) { > rmap_t rmap_flags = RMAP_NONE; > @@ -446,9 +447,16 @@ static bool remove_migration_pte(struct folio *folio, > else > folio_add_file_rmap_pte(folio, new, vma); > set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); > + > + nr_ptes++; > } > - if (READ_ONCE(vma->vm_flags) & VM_LOCKED) > + if (READ_ONCE(vma->vm_flags) & VM_LOCKED) { > + if (folio_test_large(folio) && > + nr_ptes == folio_nr_pages(folio) && > + !(pvmw.flags & PVMW_PGTABLE_CROSSED)) > + mlock_vma_folio(folio, vma); > mlock_drain_local(); > + } > > trace_remove_migration_pte(pvmw.address, pte_val(pte), > compound_order(new));