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Mon, 20 Jan 2025 14:32:21 +0800 Subject: Re: [PATCH v2 3/3] mm: memory-hotplug: check folio ref count first in do_migrate_rang To: Wupeng Ma CC: , , , , , , References: <20250116061657.227027-1-mawupeng1@huawei.com> <20250116061657.227027-4-mawupeng1@huawei.com> From: Miaohe Lin Message-ID: <3b993af4-1fe2-b250-5d07-5840f1ad530d@huawei.com> Date: Mon, 20 Jan 2025 14:32:20 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20250116061657.227027-4-mawupeng1@huawei.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.173.127.72] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemd200019.china.huawei.com (7.221.188.193) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3183640010 X-Stat-Signature: qkpu67jn4peiztywim6qci4anh5skstd X-Rspam-User: X-HE-Tag: 1737354745-798754 X-HE-Meta: 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 DuX+5Owp vfqZxEjZ0hwRCHp5WNk/wi5+ZSPXCBDTTSP0TbL3TLciVb1HzaHF9rsIo/DltOP7Hs76GjFHPHxqoioC8rCTt8NrKvIJZ6exw/GSy4g2QZ5zhfZVkVanaRAx45G4/gD2siRut4jhnc8rLMeVMmVLPGh2sMtXI1NKQDXmG2Npg/cfIGDNfoYXb4oK67FKBftVsWiSpZ6fjgRMzREadaUY9gZLhTNJwm84LH13rC9jbLnHmHuq0dJAAh9pePWPm8zswuUcQjOBJv3/b8wE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/1/16 14:16, Wupeng Ma wrote: > From: Ma Wupeng > > If a folio has an increased reference count, folio_try_get() will acquire > it, perform necessary operations, and then release it. In the case of a > poisoned folio without an elevated reference count (which is unlikely for > memory-failure), folio_try_get() will simply bypass it. > > Therefore, relocate the folio_try_get() function, responsible for checking > and acquiring this reference count at first. > > Signed-off-by: Ma Wupeng > --- > mm/memory_hotplug.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 2815bd4ea483..3fb75ee185c6 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1786,6 +1786,9 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > page = pfn_to_page(pfn); > folio = page_folio(page); > > + if (!folio_try_get(folio)) > + continue; > + > /* > * No reference or lock is held on the folio, so it might > * be modified concurrently (e.g. split). As such, > @@ -1795,12 +1798,6 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > if (folio_test_large(folio)) > pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1; > > - /* > - * HWPoison pages have elevated reference counts so the migration would > - * fail on them. It also doesn't make any sense to migrate them in the > - * first place. Still try to unmap such a page in case it is still mapped > - * (keep the unmap as the catch all safety net). > - */ > if (folio_test_hwpoison(folio) || > (folio_test_large(folio) && folio_test_has_hwpoisoned(folio))) { > if (WARN_ON(folio_test_lru(folio))) > @@ -1811,12 +1808,9 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > folio_unlock(folio); > } > > - continue; > + goto put_folio; > } > > - if (!folio_try_get(folio)) > - continue; > - > if (unlikely(page_folio(page) != folio)) > goto put_folio; Will it be necessary to move this check above folio_test_hwpoison trunk too? Thanks. .