提交 34bbd704 编写于 作者: O Oleg Nesterov 提交者: Linus Torvalds

[PATCH] adapt page_lock_anon_vma() to PREEMPT_RCU

page_lock_anon_vma() uses spin_lock() to block RCU.  This doesn't work with
PREEMPT_RCU, we have to do rcu_read_lock() explicitely.  Otherwise, it is
theoretically possible that slab returns anon_vma's memory to the system
before we do spin_unlock(&anon_vma->lock).

[ Hugh points out that this only matters for PREEMPT_RCU, which isn't merged
  yet, and may never be.  Regardless, this patch is conceptually the
  right thing to do, even if it doesn't matter at this point.  - Linus ]
Signed-off-by: NOleg Nesterov <oleg@tv-sign.ru>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Acked-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
上级 48dba8ab
...@@ -183,7 +183,7 @@ void __init anon_vma_init(void) ...@@ -183,7 +183,7 @@ void __init anon_vma_init(void)
*/ */
static struct anon_vma *page_lock_anon_vma(struct page *page) static struct anon_vma *page_lock_anon_vma(struct page *page)
{ {
struct anon_vma *anon_vma = NULL; struct anon_vma *anon_vma;
unsigned long anon_mapping; unsigned long anon_mapping;
rcu_read_lock(); rcu_read_lock();
...@@ -195,9 +195,16 @@ static struct anon_vma *page_lock_anon_vma(struct page *page) ...@@ -195,9 +195,16 @@ static struct anon_vma *page_lock_anon_vma(struct page *page)
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
spin_lock(&anon_vma->lock); spin_lock(&anon_vma->lock);
return anon_vma;
out: out:
rcu_read_unlock(); rcu_read_unlock();
return anon_vma; return NULL;
}
static void page_unlock_anon_vma(struct anon_vma *anon_vma)
{
spin_unlock(&anon_vma->lock);
rcu_read_unlock();
} }
/* /*
...@@ -333,7 +340,8 @@ static int page_referenced_anon(struct page *page) ...@@ -333,7 +340,8 @@ static int page_referenced_anon(struct page *page)
if (!mapcount) if (!mapcount)
break; break;
} }
spin_unlock(&anon_vma->lock);
page_unlock_anon_vma(anon_vma);
return referenced; return referenced;
} }
...@@ -802,7 +810,8 @@ static int try_to_unmap_anon(struct page *page, int migration) ...@@ -802,7 +810,8 @@ static int try_to_unmap_anon(struct page *page, int migration)
if (ret == SWAP_FAIL || !page_mapped(page)) if (ret == SWAP_FAIL || !page_mapped(page))
break; break;
} }
spin_unlock(&anon_vma->lock);
page_unlock_anon_vma(anon_vma);
return ret; return ret;
} }
......
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