From b2a403fdd15e5ac0c2160362de1464add6f651e1 Mon Sep 17 00:00:00 2001 From: Thomas Hellstrom Date: Wed, 1 Apr 2020 21:07:42 -0700 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. Signed-off-by: Thomas Hellstrom Signed-off-by: Andrew Morton Reviewed-by: Steven Price Cc: Andrew Morton Link: http://lkml.kernel.org/r/20200203154305.15045-1-thomas_os@shipmail.org Signed-off-by: Linus Torvalds --- mm/mapping_dirty_helpers.c | 42 ++++++++++++++++++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 4 deletions(-) (limited to 'mm/mapping_dirty_helpers.c') diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c index 71070dda9643..2c7d03675903 100644 --- a/mm/mapping_dirty_helpers.c +++ b/mm/mapping_dirty_helpers.c @@ -111,26 +111,60 @@ static int clean_record_pte(pte_t *pte, unsigned long addr, 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)); -- cgit v1.2.3