From patchwork Tue Feb 13 21:55:18 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zi Yan X-Patchwork-Id: 200688 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a05:7300:bc8a:b0:106:860b:bbdd with SMTP id dn10csp836264dyb; Tue, 13 Feb 2024 14:11:24 -0800 (PST) X-Forwarded-Encrypted: i=3; AJvYcCXOLILAdl2bQsh3j0RZR7GHbOYtHInfTQiIT2GKrotWkZQnO8WIMytwc2y+zMysYlJkGPl8eQ/QJWd6u97Zp7803XlUZQ== X-Google-Smtp-Source: AGHT+IGw8nXt3AyXX8d+OEaj29J0Srac6LN3v9DnkWLXybHRo9f1aZsjcxHuJuX13QFk5BVqhu1N X-Received: by 2002:a05:6a20:9d90:b0:19e:a19f:f4de with SMTP id mu16-20020a056a209d9000b0019ea19ff4demr954909pzb.41.1707862283964; Tue, 13 Feb 2024 14:11:23 -0800 (PST) ARC-Seal: i=2; a=rsa-sha256; t=1707862283; cv=pass; d=google.com; s=arc-20160816; b=cqoogxW0JKNGg5GFrR7IxKpWXewM7YChozlYKW/LG747uKCn2n+UnW2vKTqCC+vi86 a+KI87VfyOmK9Wz2x7bLVzIEN+31IKChcSjmlJYlbwfUpuqm+EjzW5xUD7MWSnG+b3AG ZYvZHMccsra3m3ybLK+8EqK7QiFB1mfe32Iw7h7xxteVyEuyIoJFk7TNZca3HWaOs1tp esgHxTzhEwpzFzaHjP+vYhyClT9rzYEo0uS/MyWBsTWjdIaX/0feVFkm44OczoAbj9Z7 Xk0h4kv5tbTYU0zTgipI0a+lYeKmYq/oK713k6/YE0qhagDNNA0Wo3Jbc1LK5q8VpKMO CGMg== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:list-unsubscribe :list-subscribe:list-id:precedence:reply-to:references:in-reply-to :message-id:date:subject:cc:to:from:feedback-id:dkim-signature :dkim-signature; bh=53gxtX7iv4MMGU2MQP7E5gE5detLt5TaDUQanNQvBhI=; fh=LUfFLUKn9BEJem6ixCK/ynDAykKgkLx2+U8g5THdq94=; b=Y29ZiwaYSG6IRY3Q4YUdc5gpM9d1Ma+yijtF3xuRNHSyyh2EPXqDss4D2gB9Lb+dlO VgD9rKrTBrzbM5KrVnrY73wr5O+TqYEtQzSkuqiVid1PpOCp4EVTGtLQK/Lr9KiTHDnB M6hZXIRGy5w6HCwjygkzLdhait/9elF/3j6qKjrw0HIsV2Dx9NIxz5LUu93wY5IKMYH7 3gBvIaB3G8u2f74+pMBdnOOVUWoQI0FPbqLBvkw3hIsnXp6Xu4f8w+T+wgJVinN8z3ah cbXBVYoE7NDJi6bTe8rwchGFAgOX/yRdxhvq0+p92FYrFezvfKc7NEnl6TUDhbMN5N/J Ud5w==; dara=google.com ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@sent.com header.s=fm3 header.b=xNCr4Eyx; dkim=pass header.i=@messagingengine.com header.s=fm3 header.b=kTV0K89w; arc=pass (i=1 spf=pass spfdomain=sent.com dkim=pass dkdomain=sent.com dkim=pass dkdomain=messagingengine.com dmarc=pass fromdomain=sent.com); spf=pass (google.com: domain of linux-kernel+bounces-64395-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) smtp.mailfrom="linux-kernel+bounces-64395-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=sent.com X-Forwarded-Encrypted: i=2; AJvYcCXRWupnc6WPFVH5yMe8gR4Owp6uJTqt+ry8lXX2ezRKIU6GtpRZpoXPCF6wGB97UqhjfgsUsUU1vCzp7LljiSsNXlubMA== Received: from sv.mirrors.kernel.org (sv.mirrors.kernel.org. [139.178.88.99]) by mx.google.com with ESMTPS id p16-20020a1709027ed000b001db535f1530si361568plb.419.2024.02.13.14.11.23 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Feb 2024 14:11:23 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel+bounces-64395-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99; Authentication-Results: mx.google.com; dkim=pass header.i=@sent.com header.s=fm3 header.b=xNCr4Eyx; dkim=pass header.i=@messagingengine.com header.s=fm3 header.b=kTV0K89w; arc=pass (i=1 spf=pass spfdomain=sent.com dkim=pass dkdomain=sent.com dkim=pass dkdomain=messagingengine.com dmarc=pass fromdomain=sent.com); spf=pass (google.com: domain of linux-kernel+bounces-64395-ouuuleilei=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) smtp.mailfrom="linux-kernel+bounces-64395-ouuuleilei=gmail.com@vger.kernel.org"; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=sent.com Received: from smtp.subspace.kernel.org (wormhole.subspace.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sv.mirrors.kernel.org (Postfix) with ESMTPS id A45A52871FC for ; Tue, 13 Feb 2024 22:00:25 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0A941651BB; Tue, 13 Feb 2024 21:56:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sent.com header.i=@sent.com header.b="xNCr4Eyx"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="kTV0K89w" Received: from out5-smtp.messagingengine.com (out5-smtp.messagingengine.com [66.111.4.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B439C62156; Tue, 13 Feb 2024 21:55:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=66.111.4.29 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707861354; cv=none; b=K0mlsU9fOcoN7eyV8+b+Fb+O99kNa4gy+IxpI2Xj3ybuum2L0F4g2+v9rMyWLAQViNBaI19xhA1tKo+I0kft5FWz+AUTVGxDXgNr0qxfwWtZ1+B+SAD5GnE39O948/+GUc2/qXssNGT4MBkPrXa0CFNVQbQFuJm0AaIYMWp//Hc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707861354; c=relaxed/simple; bh=JHkEikCgY3i/2eUJc8+QZcCJfr8NUuDadSm26SoKiOQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=gAY1e5ygThTC0fF5kWJTqIKRDy6TBlehfaBqjgHrjQ1vClGvclPDqR8yJkoPybEGJlw2gHSe06gOgqsjWjYTmFghtjQ35CrjgBaym3Wj6UkExu6XmHN+1ytyrpFu1akQBkPzhjd4nnKoYGVB3vREP1dKAgWbSiZrX+dz26g1Y10= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sent.com; spf=pass smtp.mailfrom=sent.com; dkim=pass (2048-bit key) header.d=sent.com header.i=@sent.com header.b=xNCr4Eyx; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b=kTV0K89w; arc=none smtp.client-ip=66.111.4.29 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sent.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sent.com Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailout.nyi.internal (Postfix) with ESMTP id CDA975C010C; Tue, 13 Feb 2024 16:55:50 -0500 (EST) Received: from mailfrontend2 ([10.202.2.163]) by compute5.internal (MEProxy); Tue, 13 Feb 2024 16:55:50 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sent.com; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:reply-to:subject:subject:to:to; s=fm3; t= 1707861350; x=1707947750; bh=53gxtX7iv4MMGU2MQP7E5gE5detLt5TaDUQ anNQvBhI=; b=xNCr4EyxjGxqd5ULfKK3OPD5KTVkU9NXO+Lzcrk0IOhb4mSXvlq UcfsCv9V6oLlEwlMByomljWq8tGq7IoO5kc9DLSJKn97sNF/wCRtYLb+l+UFfPQK lWuhXmydaRbO9+/OnoXoPiuoPP7gK61p5wJzd4wI/ku3tkYP6a/aan4szsYsZ6dF xtaIFU1UP1kRIflWHy90+v4V0+MwGNMiasr3yA0H35nShrUfxxzwMP5Zwlu+jafz g6Q6K44gxCWbjhLjib6CT2N0u5YF056zZ3lijA+vlMIaT3QZ6pEftWnFkvC3/vIQ JuTdL78x+/59LVC0ilI1UbBmoMZPR/Ea5VQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:reply-to:subject:subject:to:to:x-me-proxy :x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t= 1707861350; x=1707947750; bh=53gxtX7iv4MMGU2MQP7E5gE5detLt5TaDUQ anNQvBhI=; b=kTV0K89wR4dDFy2qyiolbWIpksbaSJ3bo6a7ddpoRpQiRviYWSe 7IxKMPBhhrDQUulsuPyI/9FGyErLQLPENI7Z5yXfK8aTj/kiovVBxIe6liP70IEI KBmyUdPW5F5KMdJkIu+otGExEiashwZ1GMhbG0Wa2+ujjLHoc4NudbSpk3gE7fIn uXCYOTW1oliAQuvnZh6FXjpqKkBfu5badMEpa/tXUg5yAXZ+q22ApxUhsy3UCTma zdwrfq0KS0g1L+o6168BHfZViCRw7tcGDIdIY+vBeVAOY/jXaoDA5DzlCyVRM9CA SmjG4sdK6XSgbNOMp+S/djUu0g1e9FGRpdg== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvledrudehgdduheegucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucdnrfhurhgthhgrshgvucdluddtmdenucfjughrpe fhvfevufffkffojghfrhggtgfgsehtkeertdertdejnecuhfhrohhmpegkihcujggrnhcu oeiiihdrhigrnhesshgvnhhtrdgtohhmqeenucggtffrrghtthgvrhhnpeejkeetkeffle elkeduffdtfedvtdejjeeutdeutdetgeejgfevtdefudejkeeiveenucevlhhushhtvghr ufhiiigvpedtnecurfgrrhgrmhepmhgrihhlfhhrohhmpeiiihdrhigrnhesshgvnhhtrd gtohhm X-ME-Proxy: Feedback-ID: iccd040f4:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Tue, 13 Feb 2024 16:55:50 -0500 (EST) From: Zi Yan To: "Pankaj Raghav (Samsung)" , linux-mm@kvack.org Cc: Zi Yan , "Matthew Wilcox (Oracle)" , David Hildenbrand , Yang Shi , Yu Zhao , "Kirill A . Shutemov" , Ryan Roberts , =?utf-8?q?Michal_Koutn=C3=BD?= , Roman Gushchin , "Zach O'Keefe" , Hugh Dickins , Mcgrof Chamberlain , Andrew Morton , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v4 5/7] mm: thp: split huge page to any lower order pages (except order-1). Date: Tue, 13 Feb 2024 16:55:18 -0500 Message-ID: <20240213215520.1048625-6-zi.yan@sent.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240213215520.1048625-1-zi.yan@sent.com> References: <20240213215520.1048625-1-zi.yan@sent.com> Reply-To: Zi Yan Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1790823402409713584 X-GMAIL-MSGID: 1790823402409713584 From: Zi Yan To split a THP to any lower order (except order-1) pages, we need to reform THPs on subpages at given order and add page refcount based on the new page order. Also we need to reinitialize page_deferred_list after removing the page from the split_queue, otherwise a subsequent split will see list corruption when checking the page_deferred_list again. It has many uses, like minimizing the number of pages after truncating a huge pagecache page. For anonymous THPs, we can only split them to order-0 like before until we add support for any size anonymous THPs. Order-1 folio is not supported because _deferred_list, which is used by partially mapped folios, is stored in subpage 2 and an order-1 folio only has subpage 0 and 1. Signed-off-by: Zi Yan --- include/linux/huge_mm.h | 21 +++++--- mm/huge_memory.c | 114 +++++++++++++++++++++++++++++++--------- 2 files changed, 101 insertions(+), 34 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 5adb86af35fc..de0c89105076 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -265,10 +265,11 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, void folio_prep_large_rmappable(struct folio *folio); bool can_split_folio(struct folio *folio, int *pextra_pins); -int split_huge_page_to_list(struct page *page, struct list_head *list); +int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, + unsigned int new_order); static inline int split_huge_page(struct page *page) { - return split_huge_page_to_list(page, NULL); + return split_huge_page_to_list_to_order(page, NULL, 0); } void deferred_split_folio(struct folio *folio); @@ -422,7 +423,8 @@ can_split_folio(struct folio *folio, int *pextra_pins) return false; } static inline int -split_huge_page_to_list(struct page *page, struct list_head *list) +split_huge_page_to_list_to_order(struct page *page, struct list_head *list, + unsigned int new_order) { return 0; } @@ -519,17 +521,20 @@ static inline bool thp_migration_supported(void) } #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ -static inline int split_folio_to_list(struct folio *folio, - struct list_head *list) +static inline int split_folio_to_list_to_order(struct folio *folio, + struct list_head *list, int new_order) { - return split_huge_page_to_list(&folio->page, list); + return split_huge_page_to_list_to_order(&folio->page, list, new_order); } -static inline int split_folio(struct folio *folio) +static inline int split_folio_to_order(struct folio *folio, int new_order) { - return split_folio_to_list(folio, NULL); + return split_folio_to_list_to_order(folio, NULL, new_order); } +#define split_folio_to_list(f, l) split_folio_to_list_to_order(f, l, 0) +#define split_folio(f) split_folio_to_order(f, 0) + /* * archs that select ARCH_WANTS_THP_SWAP but don't support THP_SWP due to * limitations in the implementation like arm64 MTE can override this to diff --git a/mm/huge_memory.c b/mm/huge_memory.c index ad7133c97428..d0e555a8ea98 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2718,11 +2718,14 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, static void unmap_folio(struct folio *folio) { - enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD | - TTU_SYNC | TTU_BATCH_FLUSH; + enum ttu_flags ttu_flags = TTU_RMAP_LOCKED | TTU_SYNC | + TTU_BATCH_FLUSH; VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); + if (folio_test_pmd_mappable(folio)) + ttu_flags |= TTU_SPLIT_HUGE_PMD; + /* * Anon pages need migration entries to preserve them, but file * pages can simply be left unmapped, then faulted back on demand. @@ -2756,7 +2759,6 @@ static void lru_add_page_tail(struct page *head, struct page *tail, struct lruvec *lruvec, struct list_head *list) { VM_BUG_ON_PAGE(!PageHead(head), head); - VM_BUG_ON_PAGE(PageCompound(tail), head); VM_BUG_ON_PAGE(PageLRU(tail), head); lockdep_assert_held(&lruvec->lru_lock); @@ -2777,7 +2779,8 @@ static void lru_add_page_tail(struct page *head, struct page *tail, } static void __split_huge_page_tail(struct folio *folio, int tail, - struct lruvec *lruvec, struct list_head *list) + struct lruvec *lruvec, struct list_head *list, + unsigned int new_order) { struct page *head = &folio->page; struct page *page_tail = head + tail; @@ -2847,10 +2850,15 @@ static void __split_huge_page_tail(struct folio *folio, int tail, * which needs correct compound_head(). */ clear_compound_head(page_tail); + if (new_order) { + prep_compound_page(page_tail, new_order); + folio_prep_large_rmappable(page_folio(page_tail)); + } /* Finally unfreeze refcount. Additional reference from page cache. */ - page_ref_unfreeze(page_tail, 1 + (!folio_test_anon(folio) || - folio_test_swapcache(folio))); + page_ref_unfreeze(page_tail, + 1 + ((!folio_test_anon(folio) || folio_test_swapcache(folio)) ? + folio_nr_pages(page_folio(page_tail)) : 0)); if (folio_test_young(folio)) folio_set_young(new_folio); @@ -2868,7 +2876,7 @@ static void __split_huge_page_tail(struct folio *folio, int tail, } static void __split_huge_page(struct page *page, struct list_head *list, - pgoff_t end) + pgoff_t end, unsigned int new_order) { struct folio *folio = page_folio(page); struct page *head = &folio->page; @@ -2877,10 +2885,11 @@ static void __split_huge_page(struct page *page, struct list_head *list, unsigned long offset = 0; unsigned int nr = thp_nr_pages(head); int i, nr_dropped = 0; + unsigned int new_nr = 1 << new_order; int order = folio_order(folio); /* complete memcg works before add pages to LRU */ - split_page_memcg(head, order, 0); + split_page_memcg(head, order, new_order); if (folio_test_anon(folio) && folio_test_swapcache(folio)) { offset = swp_offset(folio->swap); @@ -2893,8 +2902,8 @@ static void __split_huge_page(struct page *page, struct list_head *list, ClearPageHasHWPoisoned(head); - for (i = nr - 1; i >= 1; i--) { - __split_huge_page_tail(folio, i, lruvec, list); + for (i = nr - new_nr; i >= new_nr; i -= new_nr) { + __split_huge_page_tail(folio, i, lruvec, list, new_order); /* Some pages can be beyond EOF: drop them from page cache */ if (head[i].index >= end) { struct folio *tail = page_folio(head + i); @@ -2910,29 +2919,41 @@ static void __split_huge_page(struct page *page, struct list_head *list, __xa_store(&head->mapping->i_pages, head[i].index, head + i, 0); } else if (swap_cache) { + /* + * split anonymous THPs (including swapped out ones) to + * non-zero order not supported + */ + VM_WARN_ONCE(new_order, + "Split swap-cached anon folio to non-0 order not supported"); __xa_store(&swap_cache->i_pages, offset + i, head + i, 0); } } - ClearPageCompound(head); + if (!new_order) + ClearPageCompound(head); + else { + struct folio *new_folio = (struct folio *)head; + + folio_set_order(new_folio, new_order); + } unlock_page_lruvec(lruvec); /* Caller disabled irqs, so they are still disabled here */ - split_page_owner(head, order, 0); + split_page_owner(head, order, new_order); /* See comment in __split_huge_page_tail() */ if (PageAnon(head)) { /* Additional pin to swap cache */ if (PageSwapCache(head)) { - page_ref_add(head, 2); + page_ref_add(head, 1 + new_nr); xa_unlock(&swap_cache->i_pages); } else { page_ref_inc(head); } } else { /* Additional pin to page cache */ - page_ref_add(head, 2); + page_ref_add(head, 1 + new_nr); xa_unlock(&head->mapping->i_pages); } local_irq_enable(); @@ -2944,7 +2965,15 @@ static void __split_huge_page(struct page *page, struct list_head *list, if (folio_test_swapcache(folio)) split_swap_cluster(folio->swap); - for (i = 0; i < nr; i++) { + /* + * set page to its compound_head when split to non order-0 pages, so + * we can skip unlocking it below, since PG_locked is transferred to + * the compound_head of the page and the caller will unlock it. + */ + if (new_order) + page = compound_head(page); + + for (i = 0; i < nr; i += new_nr) { struct page *subpage = head + i; if (subpage == page) continue; @@ -2978,29 +3007,35 @@ bool can_split_folio(struct folio *folio, int *pextra_pins) } /* - * This function splits huge page into normal pages. @page can point to any - * subpage of huge page to split. Split doesn't change the position of @page. + * This function splits huge page into pages in @new_order. @page can point to + * any subpage of huge page to split. Split doesn't change the position of + * @page. + * + * NOTE: order-1 folio is not supported because _deferred_list, which is used + * by partially mapped folios, is stored in subpage 2 and an order-1 folio + * only has subpage 0 and 1. * * Only caller must hold pin on the @page, otherwise split fails with -EBUSY. * The huge page must be locked. * * If @list is null, tail pages will be added to LRU list, otherwise, to @list. * - * Both head page and tail pages will inherit mapping, flags, and so on from - * the hugepage. + * Pages in new_order will inherit mapping, flags, and so on from the hugepage. * - * GUP pin and PG_locked transferred to @page. Rest subpages can be freed if - * they are not mapped. + * GUP pin and PG_locked transferred to @page or the compound page @page belongs + * to. Rest subpages can be freed if they are not mapped. * * Returns 0 if the hugepage is split successfully. * Returns -EBUSY if the page is pinned or if anon_vma disappeared from under * us. */ -int split_huge_page_to_list(struct page *page, struct list_head *list) +int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, + unsigned int new_order) { struct folio *folio = page_folio(page); struct deferred_split *ds_queue = get_deferred_split_queue(folio); - XA_STATE(xas, &folio->mapping->i_pages, folio->index); + /* reset xarray order to new order after split */ + XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order); struct anon_vma *anon_vma = NULL; struct address_space *mapping = NULL; int extra_pins, ret; @@ -3010,6 +3045,26 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); + /* Cannot split THP to order-1 (no order-1 THPs) */ + if (new_order == 1) { + VM_WARN_ONCE(1, "Cannot split to order-1 folio"); + return -EINVAL; + } + + if (new_order) { + /* Split shmem folio to non-zero order not supported */ + if (shmem_mapping(folio->mapping)) { + VM_WARN_ONCE(1, "Split shmem folio to non-0 order not support"); + return -EINVAL; + } + /* No split if the file system does not support large folio */ + if (!mapping_large_folio_support(folio->mapping)) { + VM_WARN_ONCE(1, "Split file folio to non-0 order not support"); + return -EINVAL; + } + } + + is_hzp = is_huge_zero_page(&folio->page); if (is_hzp) { pr_warn_ratelimited("Called split_huge_page for huge zero page\n"); @@ -3105,14 +3160,21 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) if (folio_ref_freeze(folio, 1 + extra_pins)) { if (!list_empty(&folio->_deferred_list)) { ds_queue->split_queue_len--; - list_del(&folio->_deferred_list); + /* + * Reinitialize page_deferred_list after removing the + * page from the split_queue, otherwise a subsequent + * split will see list corruption when checking the + * page_deferred_list. + */ + list_del_init(&folio->_deferred_list); } spin_unlock(&ds_queue->split_queue_lock); if (mapping) { int nr = folio_nr_pages(folio); xas_split(&xas, folio, folio_order(folio)); - if (folio_test_pmd_mappable(folio)) { + if (folio_test_pmd_mappable(folio) && + new_order < HPAGE_PMD_ORDER) { if (folio_test_swapbacked(folio)) { __lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr); @@ -3124,7 +3186,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } } - __split_huge_page(page, list, end); + __split_huge_page(page, list, end, new_order); ret = 0; } else { spin_unlock(&ds_queue->split_queue_lock);