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Thu, 29 Aug 2024 09:34:57 +0800 Message-ID: Date: Thu, 29 Aug 2024 09:34:57 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/4] mm: compaction: convert to folio_isolate_movable() Content-Language: en-US To: Baolin Wang , Vishal Moola CC: Andrew Morton , David Hildenbrand , Matthew Wilcox , Zi Yan , References: <20240826040132.1202297-1-wangkefeng.wang@huawei.com> <20240826040132.1202297-3-wangkefeng.wang@huawei.com> <3f8300d9-1c21-46ad-a311-e97dc94eda08@linux.alibaba.com> <606adde7-44ff-476a-bd01-2141eb28943e@huawei.com> <66cfb4c7.050a0220.375d58.00ea@mx.google.com> <13234a3d-1b12-47a1-ab1f-bd9ebbf67b7f@linux.alibaba.com> From: Kefeng Wang In-Reply-To: <13234a3d-1b12-47a1-ab1f-bd9ebbf67b7f@linux.alibaba.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspam-User: X-Rspamd-Queue-Id: 055ED80007 X-Rspamd-Server: rspam01 X-Stat-Signature: xhhjxrpsyaajgpf7sqfh538ngc91g786 X-HE-Tag: 1724895302-109296 X-HE-Meta: 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 oudSzWg+ z7SVrgKThNFKawtKrg4DxAmsi8pWJY2uik31ieBXLb+l9Yat1BnpMUdyKes9l+VXOKfYyIMqKKpbJlGNujl7BMrWwIalHqo1Ev5XYvQBY4qdmnXD5QcNFwIExDosTzzHkOOEcy1IrBqZjaaJt73FIaNa+Iqy8/uU8Qxy/Z+RhiR4Io0izcbdpn1Dp3T54w3OmRgrTr/lYx9myWX4xWPOtZHXhCYYx+WXA05ychyR+BMVA6QtACjbtXXirgkngdYmovhk1cKpKmg3mhNJdhZjwWbRR/jRL2y5S5qkAx5utmiANga7r+DJrUvlOSylD0bIvckw0imG3CxUi6/7I3c2R1RYNFw== 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 2024/8/29 9:11, Baolin Wang wrote: > > > On 2024/8/29 07:37, Vishal Moola wrote: >> On Wed, Aug 28, 2024 at 08:36:03PM +0800, Kefeng Wang wrote: >>> >>> >>> On 2024/8/28 18:04, Baolin Wang wrote: >>>> Hi Kefeng, >>>> >>>> On 2024/8/26 12:01, Kefeng Wang wrote: >>>>> The tail page will always fail to isolate for non-lru-movable and >>>>> LRU page in isolate_migratepages_block(), so move PageTail check >>>>> ahead, then convert to use folio_isolate_movable() helper and more >>>>> folios. >>>>> >>>>> Signed-off-by: Kefeng Wang >>>>> --- >>>>>    mm/compaction.c | 32 +++++++++++++++++--------------- >>>>>    1 file changed, 17 insertions(+), 15 deletions(-) >>>>> >>>>> diff --git a/mm/compaction.c b/mm/compaction.c >>>>> index a2b16b08cbbf..aa2e8bb9fa58 100644 >>>>> --- a/mm/compaction.c >>>>> +++ b/mm/compaction.c >>>>> @@ -1074,39 +1074,41 @@ isolate_migratepages_block(struct >>>>> compact_control *cc, unsigned long low_pfn, >>>>>                } >>>>>            } >>>>> +        if (PageTail(page)) >>>>> +            goto isolate_fail; >>>>> + >>>>> +        folio = page_folio(page); >>>> >>>> I wonder if this is stable. Before page_folio(), it does not hold a >>>> reference on the page, so seems we should re-check the folio still >>>> contains this page after gaining a reference on the folio? >>> >>> Oh, you are right, so two way to avoid this, >>> >>> 1) re-check 'page_folio(page)  == folio', but this need change a little >>> more. >>> >>> 2)  directly use folio_get_nontail_page(page) here, and folio_put in the >>> following path, this will try to get for any pages, but it should be >>> accepted ? >>> >>> I'd prefer 2) but any other suggestion? >> >> I think option 2 makes sense, and simply use folio_put() on success and >> goto isolate_fail_put on failure instead of isolate_fail. >> >> With option 2, it might make sense to have folio_isolate_movable() >> expect to be passed a folio with elevated refcount. Then it could be >> treated similarly to its sister function folio_isolate_lru() and simply >> use folio_get() for its reference. > > Yes, that makes sense to me too. Thanks Vishal/Baolin, will refresh and send v2.