From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D6E2B12C80B for ; Wed, 27 Mar 2024 14:36:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711550212; cv=none; b=rnxxt9ZDGBHgncvdlK2cVY81qSI6IHCLk7sV3kgP/zEIaukI3dZVldfOJVw/oDMgGzcEXzllLohBU/rHB91Wn/YAaE50zB5VRbRdHUnESRD6abYyzkXEaPMjPVp0SFRVmTiVojrcqbCmPEs4i3qgVt0adXhFLriVMHDqwGWRpbk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711550212; c=relaxed/simple; bh=G/bmYftSW8RpdjE2Zu6JwyE59Vmeguq3tECqXoFRuKY=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=DLNU0VW8SaLzKVpehw3WOgsJg8vcPgqBef0ZdVA8FDkh+T1Yf4VDlnqkbUiYUJzSdR6hFfyPEBwF10fHvcPEd03gh1mUCco65OsmmVimyaEVIvxqgUTHD05Svi9gwrpxzRrpfTXACJ4QKXQ7G1lyWy3aQIv6WPlKhXrVgioOy+s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.174]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4V4Tk16CLmzRjng; Wed, 27 Mar 2024 22:35:53 +0800 (CST) Received: from dggpemm100001.china.huawei.com (unknown [7.185.36.93]) by mail.maildlp.com (Postfix) with ESMTPS id C248C140258; Wed, 27 Mar 2024 22:36:45 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm100001.china.huawei.com (7.185.36.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Wed, 27 Mar 2024 22:36:45 +0800 Message-ID: Date: Wed, 27 Mar 2024 22:36:44 +0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/6] mm: migrate: add isolate_movable_folio() Content-Language: en-US To: Zi Yan CC: Andrew Morton , , Miaohe Lin , Naoya Horiguchi , David Hildenbrand , Oscar Salvador , Hugh Dickins , Jonathan Corbet , , , Baolin Wang References: <20240327141034.3712697-1-wangkefeng.wang@huawei.com> <20240327141034.3712697-2-wangkefeng.wang@huawei.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm100001.china.huawei.com (7.185.36.93) On 2024/3/27 22:29, Zi Yan wrote: > On 27 Mar 2024, at 10:10, Kefeng Wang wrote: > >> Like isolate_lru_page(), make isolate_movable_page() as a wrapper >> around isolate_lru_folio(), since isolate_movable_page() always >> fails on a tail page, add a warn for tail page and return immediately. >> >> Signed-off-by: Kefeng Wang >> --- >> include/linux/migrate.h | 3 +++ >> mm/migrate.c | 41 +++++++++++++++++++++++------------------ >> 2 files changed, 26 insertions(+), 18 deletions(-) >> >> diff --git a/include/linux/migrate.h b/include/linux/migrate.h >> index f9d92482d117..a6c38ee7246a 100644 >> --- a/include/linux/migrate.h >> +++ b/include/linux/migrate.h >> @@ -70,6 +70,7 @@ int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free, >> unsigned int *ret_succeeded); >> struct folio *alloc_migration_target(struct folio *src, unsigned long private); >> bool isolate_movable_page(struct page *page, isolate_mode_t mode); >> +bool isolate_movable_folio(struct folio *folio, isolate_mode_t mode); >> >> int migrate_huge_page_move_mapping(struct address_space *mapping, >> struct folio *dst, struct folio *src); >> @@ -91,6 +92,8 @@ static inline struct folio *alloc_migration_target(struct folio *src, >> { return NULL; } >> static inline bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> { return false; } >> +static inline bool isolate_movable_folio(struct page *page, isolate_mode_t mode) >> + { return false; } >> >> static inline int migrate_huge_page_move_mapping(struct address_space *mapping, >> struct folio *dst, struct folio *src) >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 2228ca681afb..b2195b6ff32c 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -57,31 +57,29 @@ >> >> #include "internal.h" >> >> -bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> +bool isolate_movable_folio(struct folio *folio, isolate_mode_t mode) >> { >> - struct folio *folio = folio_get_nontail_page(page); >> const struct movable_operations *mops; >> >> /* >> - * Avoid burning cycles with pages that are yet under __free_pages(), >> + * Avoid burning cycles with folios that are yet under __free_pages(), >> * or just got freed under us. >> * >> - * In case we 'win' a race for a movable page being freed under us and >> + * In case we 'win' a race for a movable folio being freed under us and >> * raise its refcount preventing __free_pages() from doing its job >> - * the put_page() at the end of this block will take care of >> - * release this page, thus avoiding a nasty leakage. >> + * the folio_put() at the end of this block will take care of >> + * release this folio, thus avoiding a nasty leakage. >> */ >> - if (!folio) >> - goto out; >> + folio_get(folio); > > You need folio_try_get() instead. Since folio_get_nontail_page() calls > get_page_unless_zero() first. Oh, indeed, will fix. > >> >> if (unlikely(folio_test_slab(folio))) >> goto out_putfolio; >> /* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */ >> smp_rmb(); >> /* >> - * Check movable flag before taking the page lock because >> - * we use non-atomic bitops on newly allocated page flags so >> - * unconditionally grabbing the lock ruins page's owner side. >> + * Check movable flag before taking the folio lock because >> + * we use non-atomic bitops on newly allocated folio flags so >> + * unconditionally grabbing the lock ruins folio's owner side. >> */ >> if (unlikely(!__folio_test_movable(folio))) >> goto out_putfolio; >> @@ -91,13 +89,13 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> goto out_putfolio; >> >> /* >> - * As movable pages are not isolated from LRU lists, concurrent >> - * compaction threads can race against page migration functions >> - * as well as race against the releasing a page. >> + * As movable folios are not isolated from LRU lists, concurrent >> + * compaction threads can race against folio migration functions >> + * as well as race against the releasing a folio. >> * >> - * In order to avoid having an already isolated movable page >> + * In order to avoid having an already isolated movable folio >> * being (wrongly) re-isolated while it is under migration, >> - * or to avoid attempting to isolate pages being released, >> + * or to avoid attempting to isolate folios being released, >> * lets be sure we have the page lock >> * before proceeding with the movable page isolation steps. >> */ >> @@ -113,7 +111,7 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> if (!mops->isolate_page(&folio->page, mode)) >> goto out_no_isolated; >> >> - /* Driver shouldn't use PG_isolated bit of page->flags */ >> + /* Driver shouldn't use PG_isolated bit of folio->flags */ >> WARN_ON_ONCE(folio_test_isolated(folio)); >> folio_set_isolated(folio); >> folio_unlock(folio); >> @@ -124,10 +122,17 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> folio_unlock(folio); >> out_putfolio: >> folio_put(folio); >> -out: >> return false; >> } >> >> +bool isolate_movable_page(struct page *page, isolate_mode_t mode) >> +{ >> + if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page")) >> + return false; > > Why bother adding a warning here? There was no warning before. Also, > after this series, isolate_movable_page() will be gone. I copy from isolate_lru_page(), but as you said, it seems useless, will remove it. Thanks. > >> + >> + return isolate_movable_folio((struct folio *)page, mode); >> +} >> + >> static void putback_movable_folio(struct folio *folio) >> { >> const struct movable_operations *mops = folio_movable_ops(folio); >> -- >> 2.27.0 > > > -- > Best Regards, > Yan, Zi