From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: [patch 081/155] mm/mapping_dirty_helpers: update huge page-table entry callbacks Date: Wed, 01 Apr 2020 21:07:42 -0700 Message-ID: <20200402040742.acLv7dgns%akpm@linux-foundation.org> References: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:58978 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726963AbgDBEHo (ORCPT ); Thu, 2 Apr 2020 00:07:44 -0400 In-Reply-To: <20200401210155.09e3b9742e1c6e732f5a7250@linux-foundation.org> Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: akpm@linux-foundation.org, linux-mm@kvack.org, mm-commits@vger.kernel.org, steven.price@arm.com, thellstrom@vmware.com, torvalds@linux-foundation.org From: Thomas Hellstrom Subject: mm/mapping_dirty_helpers: update huge page-table entry callbacks Following the update of pagewalk code commit a07984d48146 ("mm: pagewalk: add p4d_entry() and pgd_entry()") we can modify the mapping_dirty_helpers' huge page-table entry callbacks to avoid splitting when a huge pud or -pmd is encountered. Link: http://lkml.kernel.org/r/20200203154305.15045-1-thomas_os@shipmail.org Signed-off-by: Thomas Hellstrom Reviewed-by: Steven Price Cc: Andrew Morton Signed-off-by: Andrew Morton --- mm/mapping_dirty_helpers.c | 42 +++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-) --- a/mm/mapping_dirty_helpers.c~mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks +++ a/mm/mapping_dirty_helpers.c @@ -111,26 +111,60 @@ static int clean_record_pte(pte_t *pte, return 0; } -/* wp_clean_pmd_entry - The pagewalk pmd callback. */ +/* + * wp_clean_pmd_entry - The pagewalk pmd callback. + * + * Dirty-tracking should take place on the PTE level, so + * WARN() if encountering a dirty huge pmd. + * Furthermore, never split huge pmds, since that currently + * causes dirty info loss. The pagefault handler should do + * that if needed. + */ static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end, struct mm_walk *walk) { - /* Dirty-tracking should be handled on the pte level */ pmd_t pmdval = pmd_read_atomic(pmd); + if (!pmd_trans_unstable(&pmdval)) + return 0; + + if (pmd_none(pmdval)) { + walk->action = ACTION_AGAIN; + return 0; + } + + /* Huge pmd, present or migrated */ + walk->action = ACTION_CONTINUE; if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval)) WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval)); return 0; } -/* wp_clean_pud_entry - The pagewalk pud callback. */ +/* + * wp_clean_pud_entry - The pagewalk pud callback. + * + * Dirty-tracking should take place on the PTE level, so + * WARN() if encountering a dirty huge puds. + * Furthermore, never split huge puds, since that currently + * causes dirty info loss. The pagefault handler should do + * that if needed. + */ static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end, struct mm_walk *walk) { - /* Dirty-tracking should be handled on the pte level */ pud_t pudval = READ_ONCE(*pud); + if (!pud_trans_unstable(&pudval)) + return 0; + + if (pud_none(pudval)) { + walk->action = ACTION_AGAIN; + return 0; + } + + /* Huge pud */ + walk->action = ACTION_CONTINUE; if (pud_trans_huge(pudval) || pud_devmap(pudval)) WARN_ON(pud_write(pudval) || pud_dirty(pudval)); _