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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn_valid() for start pfn To: Michal Hocko Cc: akpm@linux-foundation.org, rppt@kernel.org, ying.huang@intel.com, mgorman@techsingularity.net, vbabka@suse.cz, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <9fc85cce8908938f4fd75ff50bc981c073779aa5.1682229876.git.baolin.wang@linux.alibaba.com> <7525a9f6-b431-4404-2878-898e52905d4a@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: AF95E140014 X-Rspamd-Server: rspam01 X-Stat-Signature: gqajon7xx5duj9mbk6omsqeio4jb3on8 X-HE-Tag: 1682335300-437673 X-HE-Meta: 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 vrwM87jt /ZSE5K/lXybTFmlXOOgExo6LpiXoA8jTJP8Gmd/XjScCQIN2RqEbHgCE41LHkgVPvDcSXqPANEMNm6kVnA8bk+Zczp+W7UfzLf7Iol9Z24pVsSjxOvpfJm9f50dfHvsJy4Mo9pOWjl7tm06O+X0ZcyHYQHX1jhnLkL8HnMYXi2FNAYo9E1f7MNNqfJGvSzu/OsgK82wfYvCeZxdEN/xDlX/l1KknJCkUPZ1ke/NacEGQAjVb0wqAmdwHgUorbDv4Owo8o 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: On 4/24/2023 6:54 PM, Michal Hocko wrote: > On Mon 24-04-23 18:46:40, Baolin Wang wrote: >> >> >> On 4/24/2023 5:50 PM, Michal Hocko wrote: >>> On Sun 23-04-23 18:59:10, Baolin Wang wrote: >>>> We've already used pfn_to_online_page() for start pfn to make sure >>> >>> Who is we? I do not see any note explicitly requiring that start_pfn has >>> to be valid for __pageblock_pfn_to_page. >> >> Sorry for confusing, what I mean is the __pageblock_pfn_to_page() function, >> which has used pfn_to_online_page() for start pfn. So the pfn_valid() in >> __pageblock_pfn_to_page() for start pfn is unnecessary. >> >> I will update the commit log to make it clear. > > Your comment suggested that the check _has_ already been done. Which is > not the case. pfn_to_online_page is called later in the function so I > guess you should rephrase as following: > > " > __pageblock_pfn_to_page currently performs both pfn_valid check and > pfn_to_online_page. The former one is redundant because the latter is a > stronger check. Drop pfn_valid. > " Yes, will change the commit log. > > With that or something going along with that. Feel free to add > Acked-by: Michal Hocko Thanks. >>>> it is online and valid, so the pfn_valid() for the start pfn is >>>> unnecessary, drop it. >>>> >>>> Signed-off-by: Baolin Wang >>>> Reviewed-by: David Hildenbrand >>>> Reviewed-by: "Huang, Ying" >>>> --- >>>> Changes from v1: >>>> - Collect reviewed tags. Thanks David and Ying. >>>> --- >>>> mm/page_alloc.c | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 9de2a18519a1..6457b64fe562 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn, >>>> /* end_pfn is one past the range we are checking */ >>>> end_pfn--; >>>> - if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn)) >>>> + if (!pfn_valid(end_pfn)) >>>> return NULL; >>>> start_page = pfn_to_online_page(start_pfn); >>>> -- >>>> 2.27.0 >>> >