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mm: Prevent parallel splits during THP migration

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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@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-7-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mel Gorman 2013-10-07 11:28:44 +01:00 committed by Ingo Molnar
parent ff9042b11a
commit b8916634b7
1 changed files with 30 additions and 14 deletions
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44
mm/huge_memory.c
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@ -1278,18 +1278,18 @@ 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())
@ -1299,12 +1299,29 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
* 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;
}
/* Serialise against migrationa and check placement check placement */
/* Otherwise wait for potential migrations and retry fault */
spin_unlock(&mm->page_table_lock);
wait_on_page_locked(page);
goto out;
}
/* 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 PMD did not change while page_table_lock was released */
spin_lock(&mm->page_table_lock);
@ -1314,14 +1331,6 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
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,
@ -1330,6 +1339,8 @@ 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:
@ -1346,6 +1357,11 @@ 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;