Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752234AbdCMPrA (ORCPT ); Mon, 13 Mar 2017 11:47:00 -0400 Received: from out1-smtp.messagingengine.com ([66.111.4.25]:43996 "EHLO out1-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752311AbdCMPqR (ORCPT ); Mon, 13 Mar 2017 11:46:17 -0400 X-ME-Sender: X-Sasl-enc: kffLJzRzPbDCGmHUUJ5O1c6M8CcdCGDQn9jXfYZ9YuQ3 1489419976 From: Zi Yan To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: kirill.shutemov@linux.intel.com, akpm@linux-foundation.org, minchan@kernel.org, vbabka@suse.cz, mgorman@techsingularity.net, mhocko@kernel.org, n-horiguchi@ah.jp.nec.com, khandual@linux.vnet.ibm.com, zi.yan@cs.rutgers.edu, dnellans@nvidia.com Subject: [PATCH v4 03/11] mm: thp: introduce separate TTU flag for thp freezing Date: Mon, 13 Mar 2017 11:44:59 -0400 Message-Id: <20170313154507.3647-4-zi.yan@sent.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170313154507.3647-1-zi.yan@sent.com> References: <20170313154507.3647-1-zi.yan@sent.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3974 Lines: 112 From: Naoya Horiguchi TTU_MIGRATION is used to convert pte into migration entry until thp split completes. This behavior conflicts with thp migration added later patches, so let's introduce a new TTU flag specifically for freezing. try_to_unmap() is used both for thp split (via freeze_page()) and page migration (via __unmap_and_move()). In freeze_page(), ttu_flag given for head page is like below (assuming anonymous thp): (TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ TTU_MIGRATION | TTU_SPLIT_HUGE_PMD) and ttu_flag given for tail pages is: (TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ TTU_MIGRATION) __unmap_and_move() calls try_to_unmap() with ttu_flag: (TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS) Now I'm trying to insert a branch for thp migration at the top of try_to_unmap_one() like below static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, unsigned long address, void *arg) { ... if (flags & TTU_MIGRATION) { if (!PageHuge(page) && PageTransCompound(page)) { set_pmd_migration_entry(page, vma, address); goto out; } } , so try_to_unmap() for tail pages called by thp split can go into thp migration code path (which converts *pmd* into migration entry), while the expectation is to freeze thp (which converts *pte* into migration entry.) I detected this failure as a "bad page state" error in a testcase where split_huge_page() is called from queue_pages_pte_range(). Signed-off-by: Naoya Horiguchi --- include/linux/rmap.h | 3 ++- mm/huge_memory.c | 2 +- mm/rmap.c | 7 ++++--- 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index fee10d744ebd..58803b6e7f82 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -93,8 +93,9 @@ enum ttu_flags { TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible * and caller guarantees they will * do a final flush if necessary */ - TTU_RMAP_LOCKED = 0x80 /* do not grab rmap lock: + TTU_RMAP_LOCKED = 0x80, /* do not grab rmap lock: * caller holds it */ + TTU_SPLIT_FREEZE = 0x100, /* freeze pte under splitting thp */ }; #ifdef CONFIG_MMU diff --git a/mm/huge_memory.c b/mm/huge_memory.c index f42d4d0a3019..e32ccbd8ee3a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2142,7 +2142,7 @@ static void freeze_page(struct page *page) VM_BUG_ON_PAGE(!PageHead(page), page); if (PageAnon(page)) - ttu_flags |= TTU_MIGRATION; + ttu_flags |= TTU_SPLIT_FREEZE; ret = try_to_unmap(page, ttu_flags); VM_BUG_ON_PAGE(ret, page); diff --git a/mm/rmap.c b/mm/rmap.c index e4391100af51..555cc7ebacf6 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1304,7 +1304,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if (flags & TTU_SPLIT_HUGE_PMD) { split_huge_pmd_address(vma, address, - flags & TTU_MIGRATION, page); + flags & TTU_SPLIT_FREEZE, page); } while (page_vma_mapped_walk(&pvmw)) { @@ -1390,7 +1390,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, */ dec_mm_counter(mm, mm_counter(page)); } else if (IS_ENABLED(CONFIG_MIGRATION) && - (flags & TTU_MIGRATION)) { + (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) { swp_entry_t entry; pte_t swp_pte; /* @@ -1521,7 +1521,8 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) * locking requirements of exec(), migration skips * temporary VMAs until after exec() completes. */ - if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page)) + if ((flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE)) + && !PageKsm(page) && PageAnon(page)) rwc.invalid_vma = invalid_migration_vma; if (flags & TTU_RMAP_LOCKED) -- 2.11.0