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b=CeklMSxH+t1ywJYYBhorrm9NTLcePAfRB4gGZemyHWyXGP3HmFkmtHv5pqG0pBX8X vh/6FezOIJX/Yt/kZj7//FmRaJ2o968Ph2A1zbK0pEc8o2RRSxvB8xhvuvzXfzCxgW sLYrUmaBqvYQJilJfflRLoYBo1hyHZ+sfOhJAU0n2kAkOf9AbvXqnBrHYouplgo3pX DBXA91pfKEym2+WtAbnLEIT4mgKCBgmdOQUNM+fUHqbQb7Pi2pgh4FKepIxbj7YnHm BIXDemZHXJh029bvM7e4dGWfpIVbc+xdZWSBDk8vJDMh2JRxxrAFV0ZvINiW3wuaeR P2scC02/RI2Hw== Date: Sat, 19 Apr 2025 10:16:34 +0300 From: Mike Rapoport To: Ruihan Li Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mm_init: Don't iterate pages below ARCH_PFN_OFFSET Message-ID: References: <20250418162727.1535335-1-lrh2000@pku.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250418162727.1535335-1-lrh2000@pku.edu.cn> X-Rspamd-Queue-Id: 54B6D20003 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: wsbd14zdpw5itaywx1inwf55xi5hszz5 X-HE-Tag: 1745047001-354897 X-HE-Meta: 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 NpiHqLYA 3lh6xDbqFTTKdBiS08xg6Oj/bFpKZ/N6NwyX+xVO1Sl/5bkqBIa0VMks97k6aE6k8pZ08FLVSysw2WqpS+Kr4ICSHFy5ffTIP6pUQBU4aPYtpnxdy+P4tgfEZ83Fp2QCU5X+Gp6GZpooS0IZy59aZ4FMYyEnRYIr1wHnGQNh8y/kWezPMSAchcc0oK8o/ZOuhYUlze/GzfwABsZQ336jzbB64+1t6u0eAj0KD6PwUo0JTQwbI54gm0mCTi3xA+1lBysdCgccFEbgRdi6QGofxSEvSafnDj/kaRR5wxdmAOxcLfJ0= 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 Sat, Apr 19, 2025 at 12:27:27AM +0800, Ruihan Li wrote: > Currently, memmap_init initializes pfn_hole with 0 instead of > ARCH_PFN_OFFSET. Then init_unavailable_range will start iterating each > page from the page at address zero to the first available page, but it > won't do anything for pages below ARCH_PFN_OFFSET because pfn_valid > won't pass. > > If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the > kernel is used as a library and loaded at a very high address), the > pointless iteration for pages below ARCH_PFN_OFFSET will take a very > long time, and the kernel will look stuck at boot time. > > This commit sets the initial value of pfn_hole to ARCH_PFN_OFFSET, which > avoids the problematic and useless iteration mentioned above. > > Fixes: 907ec5fca3dc ("mm: zero remaining unavailable struct pages") I don't think it should be backported, this does not fix a bug. > Signed-off-by: Ruihan Li > --- > mm/mm_init.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 84f14fa12..b3ae9f797 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -966,7 +966,7 @@ static void __init memmap_init_zone_range(struct zone *zone, > static void __init memmap_init(void) > { > unsigned long start_pfn, end_pfn; > - unsigned long hole_pfn = 0; > + unsigned long hole_pfn = ARCH_PFN_OFFSET; ARCH_PFN_OFFSET is defined only for FLATMEM, this won't even build for SPARSEMEM. > int i, j, zone_id = 0, nid; > > for_each_mem_pfn_range(i, MAX_NUMNODES, &start_pfn, &end_pfn, &nid) { > -- > 2.49.0 > > -- Sincerely yours, Mike.