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Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1wIXuC-000000001R0-39ZE; Thu, 30 Apr 2026 16:22:40 -0400 From: Rik van Riel To: linux-kernel@vger.kernel.org Cc: kernel-team@meta.com, linux-mm@kvack.org, david@kernel.org, willy@infradead.org, surenb@google.com, hannes@cmpxchg.org, ljs@kernel.org, ziy@nvidia.com, usama.arif@linux.dev, Rik van Riel , Rik van Riel Subject: [RFC PATCH 14/45] mm: page_alloc: extract claim_whole_block from try_to_claim_block Date: Thu, 30 Apr 2026 16:20:43 -0400 Message-ID: <20260430202233.111010-15-riel@surriel.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260430202233.111010-1-riel@surriel.com> References: <20260430202233.111010-1-riel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 21EB218000A X-Stat-Signature: cbxr4pifz1qphsxp8tukunm73mthwcsn X-HE-Tag: 1777580575-164293 X-HE-Meta: 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 h4ueJ+US 6nsCzIiJ4pR9oAiH7ATUJNaqzUDT4KSBuvYxMb667nJPK9fXqHpr13vvntApeOJAi/QFQ7QvCxD4GmV5ipX3Bkabv+B8a2Sw0wwBa19sD/zWiilFkCWTBEPMOgIsaUVqgmvn4FwlzS6BGbHJlNhBGSRBipbSkCOBIwC+XK6WCJADx+zXzRi3coWHes0NeOwZ1alswegrM7PJpJdiia00PY2AHbey4p84+UskzEZGZT5a/SPhfe49Uk7mGgl9nMv7ySYUAr/mW+DSkkJvpjmcqetr8Ig6WTHRpGBRFDPtiWYY5EGt6ir6Btheu3A03Kgdxcz53Pa/oPmosS8dRyv0iOX1THg4KuRgNrg2gXU1YU4usalAoTEQXU1Msenvww3W1omgcb5HxD3oVsyQNzCxk9CkDaKwBQw4j37tZ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Rik van Riel Extract the whole-pageblock claiming logic from try_to_claim_block() into a standalone claim_whole_block() function. This handles the PB_all_free → used transition, pageblock migratetype change, and block splitting for orders >= pageblock_order. Pure refactoring, no functional change. Prepares for reuse of this logic in the per-superpageblock free lists patch. Signed-off-by: Rik van Riel Assisted-by: Claude:claude-opus-4.7 syzkaller --- mm/page_alloc.c | 90 +++++++++++++++++++++++++++++-------------------- 1 file changed, 54 insertions(+), 36 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8b10322d5221..907ce46c060f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2731,6 +2731,57 @@ int find_suitable_fallback(struct free_area *area, unsigned int order, return -1; } +/* + * claim_whole_block - claim a free block (>= pageblock_order) for a new type + * @zone: zone containing the page + * @page: free page to claim + * @current_order: order of the free page + * @order: requested allocation order + * @new_type: migratetype to assign + * @old_type: current migratetype of the block (for free list removal) + * + * Handle the PB_all_free → used transition, change the pageblock + * migratetype, split the block down to @order, and return the page. + */ +static struct page * +claim_whole_block(struct zone *zone, struct page *page, + int current_order, int order, int new_type, int old_type) +{ + struct superpageblock *sb; + unsigned int nr_added; + unsigned long pb_pfn; + + VM_WARN_ON_ONCE(current_order < order); + + /* + * Clear PB_all_free for pageblocks being claimed. + * This path bypasses page_del_and_expand(), so we + * must handle the free→used transition here. + */ + for (pb_pfn = page_to_pfn(page); + pb_pfn < page_to_pfn(page) + (1 << current_order); + pb_pfn += pageblock_nr_pages) { + struct page *pb_page = pfn_to_page(pb_pfn); + + if (get_pfnblock_bit(pb_page, pb_pfn, PB_all_free)) { + clear_pfnblock_bit(pb_page, pb_pfn, PB_all_free); + superpageblock_pb_now_used(pb_page); + } + __spb_set_has_type(pb_page, new_type); + } + + del_page_from_free_list(page, zone, current_order, old_type); + change_pageblock_range(page, current_order, new_type); + nr_added = expand(zone, page, order, current_order, new_type); + account_freepages(zone, nr_added, new_type); + + /* Single list update after all pageblocks processed */ + sb = pfn_to_superpageblock(zone, page_to_pfn(page)); + if (sb) + spb_update_list(sb); + return page; +} + /* * This function implements actual block claiming behaviour. If order is large * enough, we can claim the whole pageblock for the requested migratetype. If @@ -2754,42 +2805,9 @@ try_to_claim_block(struct zone *zone, struct page *page, return NULL; /* Take ownership for orders >= pageblock_order */ - if (current_order >= pageblock_order) { - unsigned int nr_added; - unsigned long pb_pfn; - - /* - * Clear PB_all_free for pageblocks being claimed. - * This path bypasses page_del_and_expand(), so we - * must handle the free→used transition here. - * Use block_type (the original migratetype) because - * that's what was decremented when PB_all_free was set. - */ - for (pb_pfn = page_to_pfn(page); - pb_pfn < page_to_pfn(page) + (1 << current_order); - pb_pfn += pageblock_nr_pages) { - struct page *pb_page = pfn_to_page(pb_pfn); - - if (get_pfnblock_bit(pb_page, pb_pfn, PB_all_free)) { - clear_pfnblock_bit(pb_page, pb_pfn, PB_all_free); - superpageblock_pb_now_used(pb_page); - } - __spb_set_has_type(pb_page, start_type); - } - /* Single list update after all pageblocks processed */ - { - struct superpageblock *sb = - pfn_to_superpageblock(zone, page_to_pfn(page)); - if (sb) - spb_update_list(sb); - } - - del_page_from_free_list(page, zone, current_order, block_type); - change_pageblock_range(page, current_order, start_type); - nr_added = expand(zone, page, order, current_order, start_type); - account_freepages(zone, nr_added, start_type); - return page; - } + if (current_order >= pageblock_order) + return claim_whole_block(zone, page, current_order, order, + start_type, block_type); /* moving whole block can fail due to zone boundary conditions */ if (!prep_move_freepages_block(zone, page, &start_pfn, &free_pages, -- 2.52.0