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[66.111.4.29]) by mx.google.com with ESMTPS id i7si2579877qke.204.2019.04.03.19.01.35 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Apr 2019 19:01:35 -0700 (PDT) Received-SPF: pass (google.com: domain of zi.yan@sent.com designates 66.111.4.29 as permitted sender) client-ip=66.111.4.29; Authentication-Results: mx.google.com; dkim=pass header.i=@sent.com header.s=fm3 header.b=q6z6NMOG; dkim=pass header.i=@messagingengine.com header.s=fm2 header.b=fMkp9+Bf; spf=pass (google.com: domain of zi.yan@sent.com designates 66.111.4.29 as permitted sender) smtp.mailfrom=zi.yan@sent.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=sent.com Received: from compute3.internal (compute3.nyi.internal [10.202.2.43]) by mailout.nyi.internal (Postfix) with ESMTP id 7C0B222826; Wed, 3 Apr 2019 22:01:35 -0400 (EDT) Received: from mailfrontend2 ([10.202.2.163]) by compute3.internal (MEProxy); Wed, 03 Apr 2019 22:01:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sent.com; h=from :to:cc:subject:date:message-id:in-reply-to:references:reply-to :mime-version:content-transfer-encoding; s=fm3; bh=yK2eUC0I9aY6x 1nEEB/U0Fv2Pko7D0eSucs6UTRXLHU=; b=q6z6NMOGCfnvgFrtoi86cET1Cc2ja E3zSKbA6IHmp5gGp9/W95Aj7SnuptDIou0/g1dV6Eksldx/RrUFSBstcIR3BSOHy 1Js9KXkez7HJ5A1NdiwAJlBfgv3VnPSmmPqXFut3gQ0GtotYnZJpTuYJ7DQ0SQ6E itXy+JmonkkrUErFsNPn+/CSYF2mgsP3oFAWvXMCZ1I+Ieh7IMNBX28n1LNh7huu vvm3IwC74efbWWYmIDCXKX+QJgeYI5c4F90u8AfCg25T2mi1Q1QcM+mrVMjG/Gq8 bmk6PfVHqrV+NHavozQdYhqGS7bevriR5W1D0aAzdBa8X5c95IcoMG/mw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:date:from :in-reply-to:message-id:mime-version:references:reply-to:subject :to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s= fm2; bh=yK2eUC0I9aY6x1nEEB/U0Fv2Pko7D0eSucs6UTRXLHU=; b=fMkp9+Bf g/fn2PPQYRra7dNca9xApuTL6t1n8eZ3gOIYDly+suAEQA8lEKFFygEwigy0zthL xwbu3jYzsCgT4eQQF02+7OssBKNd1IHIG9t4qjh8fbKMiX26GHVKg9HF/dSoEghv venpMBWrAezIbOY0tPVd3HKYPArf85P5bNxKJrHrBVdT+TuS91SDQKMIakHN33cJ 4tYMDhBYcvBf/d2Tez8VIUtBrmRQ6ciCzSE/GOMYewaw98bsncKpQfn1RpbDRPy9 12b9DsqPl8BX62zv1UM2qXLl5iGOjD1snFplc7jj3IgfMmsL+X1hdL+TZMX8AR3s WN+EjFGnXY8Bcg== X-ME-Sender: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeduuddrtdeggdehudculddtuddrgedutddrtddtmd cutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfhrghsthforghilhdpqfgfvfdp uffrtefokffrpgfnqfghnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivg hnthhsucdlqddutddtmdenucfjughrpefhvffufffkofgjfhhrggfgsedtkeertdertddt necuhfhrohhmpegkihcujggrnhcuoeiiihdrhigrnhesshgvnhhtrdgtohhmqeenucfkph epvdduiedrvddvkedrudduvddrvddvnecurfgrrhgrmhepmhgrihhlfhhrohhmpeiiihdr higrnhesshgvnhhtrdgtohhmnecuvehluhhsthgvrhfuihiivgepuddt X-ME-Proxy: Received: from nvrsysarch5.nvidia.com (thunderhill.nvidia.com [216.228.112.22]) by mail.messagingengine.com (Postfix) with ESMTPA id 60CC41030F; Wed, 3 Apr 2019 22:01:33 -0400 (EDT) From: Zi Yan To: Dave Hansen , Yang Shi , Keith Busch , Fengguang Wu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Daniel Jordan , Michal Hocko , "Kirill A . Shutemov" , Andrew Morton , Vlastimil Babka , Mel Gorman , John Hubbard , Mark Hairgrove , Nitin Gupta , Javier Cabezas , David Nellans , Zi Yan Subject: [RFC PATCH 12/25] exchange pages: new page migration mechanism: exchange_pages() Date: Wed, 3 Apr 2019 19:00:33 -0700 Message-Id: <20190404020046.32741-13-zi.yan@sent.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190404020046.32741-1-zi.yan@sent.com> References: <20190404020046.32741-1-zi.yan@sent.com> Reply-To: ziy@nvidia.com MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: From: Zi Yan It exchanges two pages by unmapping both first, then exchanging the data of the pages using a u64 register, and finally remapping both pages. It saves the overheads of allocating two new pages in two back-to-back migrate_pages(). Signed-off-by: Zi Yan --- include/linux/exchange.h | 23 ++ include/linux/ksm.h | 4 + mm/Makefile | 1 + mm/exchange.c | 597 +++++++++++++++++++++++++++++++++++++++++++++++ mm/ksm.c | 35 +++ 5 files changed, 660 insertions(+) create mode 100644 include/linux/exchange.h create mode 100644 mm/exchange.c diff --git a/include/linux/exchange.h b/include/linux/exchange.h new file mode 100644 index 0000000..778068e --- /dev/null +++ b/include/linux/exchange.h @@ -0,0 +1,23 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_EXCHANGE_H +#define _LINUX_EXCHANGE_H + +#include + +struct exchange_page_info { + struct page *from_page; + struct page *to_page; + + struct anon_vma *from_anon_vma; + struct anon_vma *to_anon_vma; + + int from_page_was_mapped; + int to_page_was_mapped; + + struct list_head list; +}; + +int exchange_pages(struct list_head *exchange_list, + enum migrate_mode mode, + int reason); +#endif /* _LINUX_EXCHANGE_H */ diff --git a/include/linux/ksm.h b/include/linux/ksm.h index e48b1e4..170312d 100644 --- a/include/linux/ksm.h +++ b/include/linux/ksm.h @@ -55,6 +55,7 @@ void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc); void ksm_migrate_page(struct page *newpage, struct page *oldpage); bool reuse_ksm_page(struct page *page, struct vm_area_struct *vma, unsigned long address); +void ksm_exchange_page(struct page *to_page, struct page *from_page); #else /* !CONFIG_KSM */ @@ -92,6 +93,9 @@ static inline bool reuse_ksm_page(struct page *page, struct vm_area_struct *vma, unsigned long address) { return false; +static inline void ksm_exchange_page(struct page *to_page, + struct page *from_page) +{ } #endif /* CONFIG_MMU */ #endif /* !CONFIG_KSM */ diff --git a/mm/Makefile b/mm/Makefile index fa02a9f..5e6c591 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -45,6 +45,7 @@ obj-y += init-mm.o obj-y += memblock.o obj-y += copy_page.o +obj-y += exchange.o ifdef CONFIG_MMU obj-$(CONFIG_ADVISE_SYSCALLS) += madvise.o diff --git a/mm/exchange.c b/mm/exchange.c new file mode 100644 index 0000000..626bbea --- /dev/null +++ b/mm/exchange.c @@ -0,0 +1,597 @@ +/* + * Exchange two in-use pages. Page flags and page->mapping are exchanged + * as well. Only anonymous pages are supported. + * + * Copyright (C) 2016 NVIDIA, Zi Yan + * + * This work is licensed under the terms of the GNU GPL, version 2. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + + +#include "internal.h" + +/* + * Move a list of individual pages + */ +struct pages_to_node { + unsigned long from_addr; + int from_status; + + unsigned long to_addr; + int to_status; +}; + +struct page_flags { + unsigned int page_error :1; + unsigned int page_referenced:1; + unsigned int page_uptodate:1; + unsigned int page_active:1; + unsigned int page_unevictable:1; + unsigned int page_checked:1; + unsigned int page_mappedtodisk:1; + unsigned int page_dirty:1; + unsigned int page_is_young:1; + unsigned int page_is_idle:1; + unsigned int page_swapcache:1; + unsigned int page_writeback:1; + unsigned int page_private:1; + unsigned int __pad:3; +}; + + +static void exchange_page(char *to, char *from) +{ + u64 tmp; + int i; + + for (i = 0; i < PAGE_SIZE; i += sizeof(tmp)) { + tmp = *((u64*)(from + i)); + *((u64*)(from + i)) = *((u64*)(to + i)); + *((u64*)(to + i)) = tmp; + } +} + +static inline void exchange_highpage(struct page *to, struct page *from) +{ + char *vfrom, *vto; + + vfrom = kmap_atomic(from); + vto = kmap_atomic(to); + exchange_page(vto, vfrom); + kunmap_atomic(vto); + kunmap_atomic(vfrom); +} + +static void __exchange_gigantic_page(struct page *dst, struct page *src, + int nr_pages) +{ + int i; + struct page *dst_base = dst; + struct page *src_base = src; + + for (i = 0; i < nr_pages; ) { + cond_resched(); + exchange_highpage(dst, src); + + i++; + dst = mem_map_next(dst, dst_base, i); + src = mem_map_next(src, src_base, i); + } +} + +static void exchange_huge_page(struct page *dst, struct page *src) +{ + int i; + int nr_pages; + + if (PageHuge(src)) { + /* hugetlbfs page */ + struct hstate *h = page_hstate(src); + nr_pages = pages_per_huge_page(h); + + if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) { + __exchange_gigantic_page(dst, src, nr_pages); + return; + } + } else { + /* thp page */ + BUG_ON(!PageTransHuge(src)); + nr_pages = hpage_nr_pages(src); + } + + for (i = 0; i < nr_pages; i++) { + cond_resched(); + exchange_highpage(dst + i, src + i); + } +} + +/* + * Copy the page to its new location without polluting cache + */ +static void exchange_page_flags(struct page *to_page, struct page *from_page) +{ + int from_cpupid, to_cpupid; + struct page_flags from_page_flags, to_page_flags; + struct mem_cgroup *to_memcg = page_memcg(to_page), + *from_memcg = page_memcg(from_page); + + from_cpupid = page_cpupid_xchg_last(from_page, -1); + + from_page_flags.page_error = TestClearPageError(from_page); + from_page_flags.page_referenced = TestClearPageReferenced(from_page); + from_page_flags.page_uptodate = PageUptodate(from_page); + ClearPageUptodate(from_page); + from_page_flags.page_active = TestClearPageActive(from_page); + from_page_flags.page_unevictable = TestClearPageUnevictable(from_page); + from_page_flags.page_checked = PageChecked(from_page); + ClearPageChecked(from_page); + from_page_flags.page_mappedtodisk = PageMappedToDisk(from_page); + ClearPageMappedToDisk(from_page); + from_page_flags.page_dirty = PageDirty(from_page); + ClearPageDirty(from_page); + from_page_flags.page_is_young = test_and_clear_page_young(from_page); + from_page_flags.page_is_idle = page_is_idle(from_page); + clear_page_idle(from_page); + from_page_flags.page_swapcache = PageSwapCache(from_page); + from_page_flags.page_private = PagePrivate(from_page); + ClearPagePrivate(from_page); + from_page_flags.page_writeback = test_clear_page_writeback(from_page); + + + to_cpupid = page_cpupid_xchg_last(to_page, -1); + + to_page_flags.page_error = TestClearPageError(to_page); + to_page_flags.page_referenced = TestClearPageReferenced(to_page); + to_page_flags.page_uptodate = PageUptodate(to_page); + ClearPageUptodate(to_page); + to_page_flags.page_active = TestClearPageActive(to_page); + to_page_flags.page_unevictable = TestClearPageUnevictable(to_page); + to_page_flags.page_checked = PageChecked(to_page); + ClearPageChecked(to_page); + to_page_flags.page_mappedtodisk = PageMappedToDisk(to_page); + ClearPageMappedToDisk(to_page); + to_page_flags.page_dirty = PageDirty(to_page); + ClearPageDirty(to_page); + to_page_flags.page_is_young = test_and_clear_page_young(to_page); + to_page_flags.page_is_idle = page_is_idle(to_page); + clear_page_idle(to_page); + to_page_flags.page_swapcache = PageSwapCache(to_page); + to_page_flags.page_private = PagePrivate(to_page); + ClearPagePrivate(to_page); + to_page_flags.page_writeback = test_clear_page_writeback(to_page); + + /* set to_page */ + if (from_page_flags.page_error) + SetPageError(to_page); + if (from_page_flags.page_referenced) + SetPageReferenced(to_page); + if (from_page_flags.page_uptodate) + SetPageUptodate(to_page); + if (from_page_flags.page_active) { + VM_BUG_ON_PAGE(from_page_flags.page_unevictable, from_page); + SetPageActive(to_page); + } else if (from_page_flags.page_unevictable) + SetPageUnevictable(to_page); + if (from_page_flags.page_checked) + SetPageChecked(to_page); + if (from_page_flags.page_mappedtodisk) + SetPageMappedToDisk(to_page); + + /* Move dirty on pages not done by migrate_page_move_mapping() */ + if (from_page_flags.page_dirty) + SetPageDirty(to_page); + + if (from_page_flags.page_is_young) + set_page_young(to_page); + if (from_page_flags.page_is_idle) + set_page_idle(to_page); + + /* set from_page */ + if (to_page_flags.page_error) + SetPageError(from_page); + if (to_page_flags.page_referenced) + SetPageReferenced(from_page); + if (to_page_flags.page_uptodate) + SetPageUptodate(from_page); + if (to_page_flags.page_active) { + VM_BUG_ON_PAGE(to_page_flags.page_unevictable, from_page); + SetPageActive(from_page); + } else if (to_page_flags.page_unevictable) + SetPageUnevictable(from_page); + if (to_page_flags.page_checked) + SetPageChecked(from_page); + if (to_page_flags.page_mappedtodisk) + SetPageMappedToDisk(from_page); + + /* Move dirty on pages not done by migrate_page_move_mapping() */ + if (to_page_flags.page_dirty) + SetPageDirty(from_page); + + if (to_page_flags.page_is_young) + set_page_young(from_page); + if (to_page_flags.page_is_idle) + set_page_idle(from_page); + + /* + * Copy NUMA information to the new page, to prevent over-eager + * future migrations of this same page. + */ + page_cpupid_xchg_last(to_page, from_cpupid); + page_cpupid_xchg_last(from_page, to_cpupid); + + ksm_exchange_page(to_page, from_page); + /* + * Please do not reorder this without considering how mm/ksm.c's + * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). + */ + ClearPageSwapCache(to_page); + ClearPageSwapCache(from_page); + if (from_page_flags.page_swapcache) + SetPageSwapCache(to_page); + if (to_page_flags.page_swapcache) + SetPageSwapCache(from_page); + + +#ifdef CONFIG_PAGE_OWNER + /* exchange page owner */ + BUG(); +#endif + /* exchange mem cgroup */ + to_page->mem_cgroup = from_memcg; + from_page->mem_cgroup = to_memcg; + +} + +/* + * Replace the page in the mapping. + * + * The number of remaining references must be: + * 1 for anonymous pages without a mapping + * 2 for pages with a mapping + * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. + */ + +static int exchange_page_move_mapping(struct address_space *to_mapping, + struct address_space *from_mapping, + struct page *to_page, struct page *from_page, + enum migrate_mode mode, + int to_extra_count, int from_extra_count) +{ + int to_expected_count = 1 + to_extra_count, + from_expected_count = 1 + from_extra_count; + unsigned long from_page_index = page_index(from_page), + to_page_index = page_index(to_page); + int to_swapbacked = PageSwapBacked(to_page), + from_swapbacked = PageSwapBacked(from_page); + struct address_space *to_mapping_value = to_page->mapping, + *from_mapping_value = from_page->mapping; + + + if (!to_mapping) { + /* Anonymous page without mapping */ + if (page_count(to_page) != to_expected_count) + return -EAGAIN; + } + + if (!from_mapping) { + /* Anonymous page without mapping */ + if (page_count(from_page) != from_expected_count) + return -EAGAIN; + } + + /* + * Now we know that no one else is looking at the page: + * no turning back from here. + */ + /* from_page */ + from_page->index = to_page_index; + from_page->mapping = to_mapping_value; + + ClearPageSwapBacked(from_page); + if (to_swapbacked) + SetPageSwapBacked(from_page); + + + /* to_page */ + to_page->index = from_page_index; + to_page->mapping = from_mapping_value; + + ClearPageSwapBacked(to_page); + if (from_swapbacked) + SetPageSwapBacked(to_page); + + return MIGRATEPAGE_SUCCESS; +} + +static int exchange_from_to_pages(struct page *to_page, struct page *from_page, + enum migrate_mode mode) +{ + int rc = -EBUSY; + struct address_space *to_page_mapping, *from_page_mapping; + + VM_BUG_ON_PAGE(!PageLocked(from_page), from_page); + VM_BUG_ON_PAGE(!PageLocked(to_page), to_page); + + /* copy page->mapping not use page_mapping() */ + to_page_mapping = page_mapping(to_page); + from_page_mapping = page_mapping(from_page); + + BUG_ON(from_page_mapping); + BUG_ON(to_page_mapping); + + BUG_ON(PageWriteback(from_page)); + BUG_ON(PageWriteback(to_page)); + + /* actual page mapping exchange */ + rc = exchange_page_move_mapping(to_page_mapping, from_page_mapping, + to_page, from_page, mode, 0, 0); + /* actual page data exchange */ + if (rc != MIGRATEPAGE_SUCCESS) + return rc; + + rc = -EFAULT; + + if (PageHuge(from_page) || PageTransHuge(from_page)) + exchange_huge_page(to_page, from_page); + else + exchange_highpage(to_page, from_page); + rc = 0; + + exchange_page_flags(to_page, from_page); + + return rc; +} + +static int unmap_and_exchange(struct page *from_page, struct page *to_page, + enum migrate_mode mode) +{ + int rc = -EAGAIN; + int from_page_was_mapped = 0, to_page_was_mapped = 0; + pgoff_t from_index, to_index; + struct anon_vma *from_anon_vma = NULL, *to_anon_vma = NULL; + + /* from_page lock down */ + if (!trylock_page(from_page)) { + if ((mode & MIGRATE_MODE_MASK) == MIGRATE_ASYNC) + goto out; + + lock_page(from_page); + } + + BUG_ON(PageWriteback(from_page)); + + /* + * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, + * we cannot notice that anon_vma is freed while we migrates a page. + * This get_anon_vma() delays freeing anon_vma pointer until the end + * of migration. File cache pages are no problem because of page_lock() + * File Caches may use write_page() or lock_page() in migration, then, + * just care Anon page here. + * + * Only page_get_anon_vma() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + * But if we cannot get anon_vma, then we won't need it anyway, + * because that implies that the anon page is no longer mapped + * (and cannot be remapped so long as we hold the page lock). + */ + if (PageAnon(from_page) && !PageKsm(from_page)) + from_anon_vma = page_get_anon_vma(from_page); + + /* to_page lock down */ + if (!trylock_page(to_page)) { + if ((mode & MIGRATE_MODE_MASK) == MIGRATE_ASYNC) + goto out_unlock; + + lock_page(to_page); + } + + BUG_ON(PageWriteback(to_page)); + + /* + * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, + * we cannot notice that anon_vma is freed while we migrates a page. + * This get_anon_vma() delays freeing anon_vma pointer until the end + * of migration. File cache pages are no problem because of page_lock() + * File Caches may use write_page() or lock_page() in migration, then, + * just care Anon page here. + * + * Only page_get_anon_vma() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + * But if we cannot get anon_vma, then we won't need it anyway, + * because that implies that the anon page is no longer mapped + * (and cannot be remapped so long as we hold the page lock). + */ + if (PageAnon(to_page) && !PageKsm(to_page)) + to_anon_vma = page_get_anon_vma(to_page); + + from_index = from_page->index; + to_index = to_page->index; + + /* + * Corner case handling: + * 1. When a new swap-cache page is read into, it is added to the LRU + * and treated as swapcache but it has no rmap yet. + * Calling try_to_unmap() against a page->mapping==NULL page will + * trigger a BUG. So handle it here. + * 2. An orphaned page (see truncate_complete_page) might have + * fs-private metadata. The page can be picked up due to memory + * offlining. Everywhere else except page reclaim, the page is + * invisible to the vm, so the page can not be migrated. So try to + * free the metadata, so the page can be freed. + */ + if (!from_page->mapping) { + VM_BUG_ON_PAGE(PageAnon(from_page), from_page); + if (page_has_private(from_page)) { + try_to_free_buffers(from_page); + goto out_unlock_both; + } + } else if (page_mapped(from_page)) { + /* Establish migration ptes */ + VM_BUG_ON_PAGE(PageAnon(from_page) && !PageKsm(from_page) && + !from_anon_vma, from_page); + try_to_unmap(from_page, + TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + from_page_was_mapped = 1; + } + + if (!to_page->mapping) { + VM_BUG_ON_PAGE(PageAnon(to_page), to_page); + if (page_has_private(to_page)) { + try_to_free_buffers(to_page); + goto out_unlock_both_remove_from_migration_pte; + } + } else if (page_mapped(to_page)) { + /* Establish migration ptes */ + VM_BUG_ON_PAGE(PageAnon(to_page) && !PageKsm(to_page) && + !to_anon_vma, to_page); + try_to_unmap(to_page, + TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + to_page_was_mapped = 1; + } + + if (!page_mapped(from_page) && !page_mapped(to_page)) + rc = exchange_from_to_pages(to_page, from_page, mode); + + /* In remove_migration_ptes(), page_walk_vma() assumes + * from_page and to_page have the same index. + * Thus, we restore old_page->index here. + * Here to_page is the old_page. + */ + if (to_page_was_mapped) { + if (rc == MIGRATEPAGE_SUCCESS) + swap(to_page->index, to_index); + + remove_migration_ptes(to_page, + rc == MIGRATEPAGE_SUCCESS ? from_page : to_page, false); + + if (rc == MIGRATEPAGE_SUCCESS) + swap(to_page->index, to_index); + } + +out_unlock_both_remove_from_migration_pte: + if (from_page_was_mapped) { + if (rc == MIGRATEPAGE_SUCCESS) + swap(from_page->index, from_index); + + remove_migration_ptes(from_page, + rc == MIGRATEPAGE_SUCCESS ? to_page : from_page, false); + + if (rc == MIGRATEPAGE_SUCCESS) + swap(from_page->index, from_index); + } + + + +out_unlock_both: + if (to_anon_vma) + put_anon_vma(to_anon_vma); + unlock_page(to_page); +out_unlock: + /* Drop an anon_vma reference if we took one */ + if (from_anon_vma) + put_anon_vma(from_anon_vma); + unlock_page(from_page); +out: + + return rc; +} + +/* + * Exchange pages in the exchange_list + * + * Caller should release the exchange_list resource. + * + * */ +int exchange_pages(struct list_head *exchange_list, + enum migrate_mode mode, + int reason) +{ + struct exchange_page_info *one_pair, *one_pair2; + int failed = 0; + + list_for_each_entry_safe(one_pair, one_pair2, exchange_list, list) { + struct page *from_page = one_pair->from_page; + struct page *to_page = one_pair->to_page; + int rc; + int retry = 0; + +again: + if (page_count(from_page) == 1) { + /* page was freed from under us. So we are done */ + ClearPageActive(from_page); + ClearPageUnevictable(from_page); + + put_page(from_page); + dec_node_page_state(from_page, NR_ISOLATED_ANON + + page_is_file_cache(from_page)); + + if (page_count(to_page) == 1) { + ClearPageActive(to_page); + ClearPageUnevictable(to_page); + put_page(to_page); + } else + goto putback_to_page; + + continue; + } + + if (page_count(to_page) == 1) { + /* page was freed from under us. So we are done */ + ClearPageActive(to_page); + ClearPageUnevictable(to_page); + + put_page(to_page); + + dec_node_page_state(to_page, NR_ISOLATED_ANON + + page_is_file_cache(to_page)); + + dec_node_page_state(from_page, NR_ISOLATED_ANON + + page_is_file_cache(from_page)); + putback_lru_page(from_page); + continue; + } + + /* TODO: compound page not supported */ + if (PageCompound(from_page) || page_mapping(from_page)) { + ++failed; + goto putback; + } + + rc = unmap_and_exchange(from_page, to_page, mode); + + if (rc == -EAGAIN && retry < 3) { + ++retry; + goto again; + } + + if (rc != MIGRATEPAGE_SUCCESS) + ++failed; + +putback: + dec_node_page_state(from_page, NR_ISOLATED_ANON + + page_is_file_cache(from_page)); + + putback_lru_page(from_page); +putback_to_page: + dec_node_page_state(to_page, NR_ISOLATED_ANON + + page_is_file_cache(to_page)); + + putback_lru_page(to_page); + + } + return failed; +} diff --git a/mm/ksm.c b/mm/ksm.c index fc64874..e5b492b 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2716,6 +2716,41 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage) set_page_stable_node(oldpage, NULL); } } + +void ksm_exchange_page(struct page *to_page, struct page *from_page) +{ + struct stable_node *to_stable_node, *from_stable_node; + + VM_BUG_ON_PAGE(!PageLocked(to_page), to_page); + VM_BUG_ON_PAGE(!PageLocked(from_page), from_page); + + to_stable_node = page_stable_node(to_page); + from_stable_node = page_stable_node(from_page); + if (to_stable_node) { + VM_BUG_ON_PAGE(to_stable_node->kpfn != page_to_pfn(from_page), + from_page); + to_stable_node->kpfn = page_to_pfn(to_page); + /* + * newpage->mapping was set in advance; now we need smp_wmb() + * to make sure that the new stable_node->kpfn is visible + * to get_ksm_page() before it can see that oldpage->mapping + * has gone stale (or that PageSwapCache has been cleared). + */ + smp_wmb(); + } + if (from_stable_node) { + VM_BUG_ON_PAGE(from_stable_node->kpfn != page_to_pfn(to_page), + to_page); + from_stable_node->kpfn = page_to_pfn(from_page); + /* + * newpage->mapping was set in advance; now we need smp_wmb() + * to make sure that the new stable_node->kpfn is visible + * to get_ksm_page() before it can see that oldpage->mapping + * has gone stale (or that PageSwapCache has been cleared). + */ + smp_wmb(); + } +} #endif /* CONFIG_MIGRATION */ #ifdef CONFIG_MEMORY_HOTREMOVE -- 2.7.4