+ mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks.patch added to -mm tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



The patch titled
     Subject: mm/mapping_dirty_helpers: Update huge page-table entry callbacks
has been added to the -mm tree.  Its filename is
     mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
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@xxxxxxxxxxxx
Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 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));
 
_

Patches currently in -mm which might be from thellstrom@xxxxxxxxxx are

mm-mapping_dirty_helpers-update-huge-page-table-entry-callbacks.patch




[Index of Archives]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux