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authorThomas Hellstrom <thellstrom@vmware.com>2020-04-01 21:07:42 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:29 -0700
commitb2a403fdd15e5ac0c2160362de1464add6f651e1 (patch)
tree04fad6558694e469dcffdf11b1c76e5349e6c339 /mm
parent48fe267c503ec22014ba4e83d002b07caad034d0 (diff)
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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 <thellstrom@vmware.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Steven Price <steven.price@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/20200203154305.15045-1-thomas_os@shipmail.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mapping_dirty_helpers.c42
1 files changed, 38 insertions, 4 deletions
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));