This is a note to let you know that I've just added the patch titled
mm: Prevent parallel splits during THP migration
to the 3.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-prevent-parallel-splits-during-thp-migration.patch
and it can be found in the queue-3.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 587fe586f44a48f9691001ba6c45b86c8e4ba21f Mon Sep 17 00:00:00 2001
From: Mel Gorman <mgorman@xxxxxxx>
Date: Mon, 7 Oct 2013 11:28:44 +0100
Subject: mm: Prevent parallel splits during THP migration
From: Mel Gorman <mgorman@xxxxxxx>
commit 587fe586f44a48f9691001ba6c45b86c8e4ba21f upstream.
THP migrations are serialised by the page lock but on its own that does
not prevent THP splits. If the page is split during THP migration then
the pmd_same checks will prevent page table corruption but the unlock page
and other fix-ups potentially will cause corruption. This patch takes the
anon_vma lock to prevent parallel splits during migration.
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1381141781-10992-7-git-send-email-mgorman@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 44 ++++++++++++++++++++++++++++++--------------
1 file changed, 30 insertions(+), 14 deletions(-)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1290,18 +1290,18 @@ out:
int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pmd_t pmd, pmd_t *pmdp)
{
+ struct anon_vma *anon_vma = NULL;
struct page *page;
unsigned long haddr = addr & HPAGE_PMD_MASK;
int target_nid;
int current_nid = -1;
- bool migrated;
+ bool migrated, page_locked;
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(pmd, *pmdp)))
goto out_unlock;
page = pmd_page(pmd);
- get_page(page);
current_nid = page_to_nid(page);
count_vm_numa_event(NUMA_HINT_FAULTS);
if (current_nid == numa_node_id())
@@ -1311,12 +1311,29 @@ int do_huge_pmd_numa_page(struct mm_stru
* Acquire the page lock to serialise THP migrations but avoid dropping
* page_table_lock if at all possible
*/
- if (trylock_page(page))
- goto got_lock;
+ page_locked = trylock_page(page);
+ target_nid = mpol_misplaced(page, vma, haddr);
+ if (target_nid == -1) {
+ /* If the page was locked, there are no parallel migrations */
+ if (page_locked) {
+ unlock_page(page);
+ goto clear_pmdnuma;
+ }
+
+ /* Otherwise wait for potential migrations and retry fault */
+ spin_unlock(&mm->page_table_lock);
+ wait_on_page_locked(page);
+ goto out;
+ }
- /* Serialise against migrationa and check placement check placement */
+ /* Page is misplaced, serialise migrations and parallel THP splits */
+ get_page(page);
spin_unlock(&mm->page_table_lock);
- lock_page(page);
+ if (!page_locked) {
+ lock_page(page);
+ page_locked = true;
+ }
+ anon_vma = page_lock_anon_vma_read(page);
/* Confirm the PTE did not while locked */
spin_lock(&mm->page_table_lock);
@@ -1326,14 +1343,6 @@ int do_huge_pmd_numa_page(struct mm_stru
goto out_unlock;
}
-got_lock:
- target_nid = mpol_misplaced(page, vma, haddr);
- if (target_nid == -1) {
- unlock_page(page);
- put_page(page);
- goto clear_pmdnuma;
- }
-
/* Migrate the THP to the requested node */
spin_unlock(&mm->page_table_lock);
migrated = migrate_misplaced_transhuge_page(mm, vma,
@@ -1342,6 +1351,8 @@ got_lock:
goto check_same;
task_numa_fault(target_nid, HPAGE_PMD_NR, true);
+ if (anon_vma)
+ page_unlock_anon_vma_read(anon_vma);
return 0;
check_same:
@@ -1358,6 +1369,11 @@ clear_pmdnuma:
update_mmu_cache_pmd(vma, addr, pmdp);
out_unlock:
spin_unlock(&mm->page_table_lock);
+
+out:
+ if (anon_vma)
+ page_unlock_anon_vma_read(anon_vma);
+
if (current_nid != -1)
task_numa_fault(current_nid, HPAGE_PMD_NR, false);
return 0;
Patches currently in stable-queue which might be from mgorman@xxxxxxx are
queue-3.11/mm-wait-for-thp-migrations-to-complete-during-numa-hinting-faults.patch
queue-3.11/mm-account-for-a-thp-numa-hinting-update-as-one-pte-update.patch
queue-3.11/mm-prevent-parallel-splits-during-thp-migration.patch
queue-3.11/mm-close-races-between-thp-migration-and-pmd-numa-clearing.patch
queue-3.11/mm-numa-do-not-account-for-a-hinting-fault-if-we-raced.patch
queue-3.11/mm-numa-sanitize-task_numa_fault-callsites.patch
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