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Thu, 13 Jun 2024 18:58:44 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a6f56ed0ea4sm128453966b.116.2024.06.13.18.58.43 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Thu, 13 Jun 2024 18:58:44 -0700 (PDT) From: Wei Yang To: richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net Cc: linux-um@lists.infradead.org, linux-mm@kvack.org, Wei Yang , Jason Lunz , Jeff Dike , Paolo 'Blaisorblade' Giarrusso , Alasdair G Kergon , Jens Axboe , Andrew Morton , Mike Rapoport , David Hildenbrand Subject: [PATCH] um/mm: get max_low_pfn from memblock Date: Fri, 14 Jun 2024 01:58:40 +0000 Message-Id: <20240614015840.12632-1-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: C4A6820007 X-Stat-Signature: h8skgdwnuzuqberiexmxawgnegz4x4dq X-Rspam-User: X-HE-Tag: 1718330326-867217 X-HE-Meta: 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 nkdxZ52u 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 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: Current calculation of max_low_pfn is introduced in commit af84eab20891 ("[PATCH] uml: fix LVM crash"). It is intended to set max_low_pfn to the same value as max_pfn. But I am not sure why the max_pfn is set to totalram_pages, which represents the number of usable pages in system instead of an absolute page frame number. (The change history stops there.) While we can get the maximum page frame number from memblock, this looks more reasonable than setting to totalram_pages. Also this would help changing totalram_pages accounting, since we plan to move the accounting into __free_pages_core(). With this change, totalram_pages may not represent the total usable pages at this point, since some pages would be deferred initialized. Signed-off-by: Wei Yang CC: Jason Lunz CC: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Cc: Alasdair G Kergon Cc: Jens Axboe CC: Andrew Morton CC: Mike Rapoport (IBM) CC: David Hildenbrand --- A simple UML bootup test looks good. --- arch/um/kernel/mem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c index ca91accd64fc..ca682879e28f 100644 --- a/arch/um/kernel/mem.c +++ b/arch/um/kernel/mem.c @@ -73,7 +73,7 @@ void __init mem_init(void) /* this will put all low memory onto the freelists */ memblock_free_all(); - max_low_pfn = totalram_pages(); + max_low_pfn = PFN_DOWN(memblock_end_of_DRAM()); max_pfn = max_low_pfn; kmalloc_ok = 1; } -- 2.34.1