path: root/arch/x86/mm
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authorMel Gorman <mgorman@suse.de>2013-12-19 01:08:32 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2013-12-19 03:04:50 (GMT)
commit2b4847e73004c10ae6666c2e27b5c5430aed8698 (patch)
treef5062cda19087b1d9a6830feffc4089aeb5b7fc8 /arch/x86/mm
parentc97102ba96324da330078ad8619ba4dfe840dbe3 (diff)
mm: numa: serialise parallel get_user_page against THP migration
Base pages are unmapped and flushed from cache and TLB during normal page migration and replaced with a migration entry that causes any parallel NUMA hinting fault or gup to block until migration completes. THP does not unmap pages due to a lack of support for migration entries at a PMD level. This allows races with get_user_pages and get_user_pages_fast which commit 3f926ab945b6 ("mm: Close races between THP migration and PMD numa clearing") made worse by introducing a pmd_clear_flush(). This patch forces get_user_page (fast and normal) on a pmd_numa page to go through the slow get_user_page path where it will serialise against THP migration and properly account for the NUMA hinting fault. On the migration side the page table lock is taken for each PTE update. Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com> Cc: Alex Thorlton <athorlton@sgi.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/mm')
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index dd74e46..0596e8e 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -83,6 +83,12 @@ static noinline int gup_pte_range(pmd_t pmd, unsigned long addr,
pte_t pte = gup_get_pte(ptep);
struct page *page;
+ /* Similar to the PMD case, NUMA hinting must take slow path */
+ if (pte_numa(pte)) {
+ pte_unmap(ptep);
+ return 0;
+ }
if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
return 0;
@@ -167,6 +173,13 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
if (pmd_none(pmd) || pmd_trans_splitting(pmd))
return 0;
if (unlikely(pmd_large(pmd))) {
+ /*
+ * NUMA hinting faults need to be handled in the GUP
+ * slowpath for accounting purposes and so that they
+ * can be serialised against THP migration.
+ */
+ if (pmd_numa(pmd))
+ return 0;
if (!gup_huge_pmd(pmd, addr, next, write, pages, nr))
return 0;
} else {

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