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mm: Close races between THP migration and PMD numa clearing

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THP migration uses the page lock to guard against parallel allocations
but there are cases like this still open

  Task A					Task B
  ---------------------				---------------------
  do_huge_pmd_numa_page				do_huge_pmd_numa_page
  lock_page
  mpol_misplaced == -1
  unlock_page
  goto clear_pmdnuma
						lock_page
						mpol_misplaced == 2
						migrate_misplaced_transhuge
  pmd = pmd_mknonnuma
  set_pmd_at

During hours of testing, one crashed with weird errors and while I have
no direct evidence, I suspect something like the race above happened.
This patch extends the page lock to being held until the pmd_numa is
cleared to prevent migration starting in parallel while the pmd_numa is
being cleared. It also flushes the old pmd entry and orders pagetable
insertion before rmap insertion.

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/1381141781-10992-9-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mel Gorman
2013-10-07 11:28:46 +01:00
committed by Ingo Molnar
parent 8191acbd30
commit a54a407fbf
2 changed files with 26 additions and 26 deletions
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19
mm/migrate.c
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@@ -1713,12 +1713,12 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
unlock_page(new_page);
put_page(new_page); /* Free it */
unlock_page(page);
/* Retake the callers reference and putback on LRU */
get_page(page);
putback_lru_page(page);
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
isolated = 0;
goto out;
mod_zone_page_state(page_zone(page),
NR_ISOLATED_ANON + page_lru, -HPAGE_PMD_NR);
goto out_fail;
}
/*
@@ -1735,9 +1735,9 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
entry = pmd_mkhuge(entry);
page_add_new_anon_rmap(new_page, vma, haddr);
pmdp_clear_flush(vma, haddr, pmd);
set_pmd_at(mm, haddr, pmd, entry);
page_add_new_anon_rmap(new_page, vma, haddr);
update_mmu_cache_pmd(vma, address, &entry);
page_remove_rmap(page);
/*
@@ -1756,7 +1756,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR);
count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR);
out:
mod_zone_page_state(page_zone(page),
NR_ISOLATED_ANON + page_lru,
-HPAGE_PMD_NR);
@@ -1765,6 +1764,10 @@ out:
out_fail:
count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR);
out_dropref:
entry = pmd_mknonnuma(entry);
set_pmd_at(mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, address, &entry);
unlock_page(page);
put_page(page);
return 0;