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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH 1/8] mm/compaction: avoid missing last page block in section after skip offline sections To: Kemeng Shi , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mgorman@techsingularity.net, willy@infradead.org, david@redhat.com References: <20230728171037.2219226-1-shikemeng@huaweicloud.com> <20230728171037.2219226-2-shikemeng@huaweicloud.com> From: Baolin Wang In-Reply-To: <20230728171037.2219226-2-shikemeng@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 678D61C0044 X-Stat-Signature: zpznidzmggnbd64bqnu1y8rso4g69jhp X-Rspam-User: X-HE-Tag: 1690804853-999857 X-HE-Meta: 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 W1BvL2QX b3qviuTwTS6Knf5BBy5cwh9h5uRpk17TNJ6vyYDAlP8wbf6evc4fS4d1iQy7jQQQKaXMBzMZ9khypVcWrH0ZCZ+M9ceEJ18cRwCvLYIsMXPYOGRfCx/ej0sOMyo2iljiXocNZDiZzO0dtW8o= 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 7/29/2023 1:10 AM, Kemeng Shi wrote: > skip_offline_sections_reverse will return the last pfn in found online > section. Then we set block_start_pfn to start of page block which > contains the last pfn in section. Then we continue, move one page > block forward and ignore the last page block in the online section. > Make block_start_pfn point to first page block after online section to fix > this: > 1. make skip_offline_sections_reverse return end pfn of online section, > i.e. pfn of page block after online section. > 2. assign block_start_pfn with next_pfn. > > Fixes: f63224525309 ("mm: compaction: skip the memory hole rapidly when isolating free pages") > Signed-off-by: Kemeng Shi > --- > mm/compaction.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 9b7a0a69e19f..ce7841363b12 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -259,7 +259,7 @@ static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) > > while (start_nr-- > 0) { > if (online_section_nr(start_nr)) > - return section_nr_to_pfn(start_nr) + PAGES_PER_SECTION - 1; > + return section_nr_to_pfn(start_nr + 1); This is incorrect, you returned the start pfn of this section. > } > > return 0; > @@ -1670,8 +1670,7 @@ static void isolate_freepages(struct compact_control *cc) > > next_pfn = skip_offline_sections_reverse(block_start_pfn); > if (next_pfn) > - block_start_pfn = max(pageblock_start_pfn(next_pfn), > - low_pfn); > + block_start_pfn = max(next_pfn, low_pfn); 'block_start_pfn' should be pageblock aligned. If the 'next_pfn' is not pageblock-aligned (though this is not the common case), we should skip it. But if the 'next_pfn' is pageblock-aligned, yes, the commit f63224525309 still ignores the last pageblock, which is not right. So I think it should be: block_start_pfn = pageblock_aligned(next_pfn) ? : pageblock_start_pfn(next_pfn); block_start_pfn = max(block_start_pfn, low_pfn);