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Mon, 9 Dec 2024 21:36:40 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2zCyGehiV2dufAAAD6G6ig (envelope-from ); Mon, 09 Dec 2024 21:36:40 +0000 Message-ID: <882cb1b3-8519-46b7-b902-38a4f751b247@suse.cz> Date: Mon, 9 Dec 2024 22:36:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] mm/page_alloc: conditionally split > pageblock_order pages in free_one_page() and move_freepages_block_isolate() Content-Language: en-US To: Zi Yan Cc: David Hildenbrand , linux-kernel@vger.kernel.org, Johannes Weiner , linux-mm@kvack.org, Andrew Morton , Yu Zhao References: <20241206095951.98007-1-david@redhat.com> <20241206095951.98007-2-david@redhat.com> <37B7A92E-B58F-442D-8501-B07A507F0451@nvidia.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <37B7A92E-B58F-442D-8501-B07A507F0451@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 28769160014 X-Stat-Signature: w4496t9sji4sxzbksmxx9bdrwrf36sp3 X-Rspam-User: X-HE-Tag: 1733780187-34 X-HE-Meta: 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 Wc8RwRM5 TXAq40MemwbmFXxucJmbVf5beEwWTYBof1g1YBbQTkZbFkZhoNVM5DUhECL6YuUz8S595osJcfzKQn4nuvsmYcdUIUZ76dPC+QiE8Ks8w3NJ96mKG6brN+jTIDULNVm2sW+NTmy9m9QXqxCqLzdSZGVZatLHeLTr7PBmaUzbvzXftP+Bhz7lHKARQa28Dn+s8/Dklpbt3z6NtpvjGrTsH4HqdHl4VDRSeGK4n9Rnwf8RUapxec6SE1bmf6b3yWlyNa24BsyNvZWxQarER/HOp4I9A3GPtkV8FUxJHWbmBGpZPy7DIrFZaP//dclBpYr3IQc4vapjk0XebdfgSNkC7UDD2pwiepJUCWczHFR2/+UEnpF4= 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 12/9/24 20:23, Zi Yan wrote: > On 9 Dec 2024, at 14:01, Vlastimil Babka wrote: >>> + /* >>> + * With CONFIG_MEMORY_ISOLATION, we might be freeing MAX_ORDER_NR_PAGES >>> + * pages that cover pageblocks with different migratetypes; for example >>> + * only some migratetypes might be MIGRATE_ISOLATE. In that (unlikely) >>> + * case, fallback to freeing individual pageblocks so they get put >>> + * onto the right lists. >>> + */ >>> + if (!IS_ENABLED(CONFIG_MEMORY_ISOLATION) || >>> + likely(order <= pageblock_order) || >>> + pfnblock_migratetype_equal(pfn + pageblock_nr_pages, end_pfn, mt)) { >>> + __free_one_page(page, pfn, zone, order, mt, fpi_flags); >>> + return; >>> + } >>> >>> - __free_one_page(page, pfn, zone, order, mt, fpi); >>> - pfn += 1 << order; >>> + while (pfn != end_pfn) { >>> + mt = get_pfnblock_migratetype(page, pfn); >>> + __free_one_page(page, pfn, zone, pageblock_order, mt, fpi_flags); >>> + pfn += pageblock_nr_pages; >>> page = pfn_to_page(pfn); >> >> This predates your patch, but seems potentially dangerous to attempt >> pfn_to_page(end_pfn) with SPARSEMEM and no vmemmap and the end_pfn perhaps >> being just outside of the valid range? Should we change that? >> >> But seems this code was initially introduced as part of Johannes' >> migratetype hygiene series. > > It starts as split_free_page() from commit b2c9e2fbba32 ("mm: make > alloc_contig_range work at pageblock granularity”), but harmless since > it is only used to split a buddy page. Then commit fd919a85cd55 ("mm: > page_isolation: prepare for hygienic freelists") refactored it, which > should be fine, since it is still used for the same purpose in page > isolation. Then commit e98337d11bbd ("mm/contig_alloc: support __GFP_COMP") > used it for gigantic hugetlb. > > For SPARSEMEM && !SPARSEMEM_VMEMMAP, PFNs are contiguous, vmemmap might not > be. The code above using pfn in the loop might be fine. And since order > is provided, unless the caller is providing a falsely large order, pfn > should be valid. Or am I missing anything? I mean if we are in the last iteration and about to exit the loop because pfn == end_pfn, and it's the very last MAX_ORDER block of a zone and section, end_pfn is already outside of it, and pfn_to_page() might get NULL result from __pfn_to_section() and __section_mem_map_addr() then oops, no? > Best Regards, > Yan, Zi