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Commit 34bbd704 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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[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: default avatarOleg 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: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 48dba8ab

mm/rmap.c

+13 −4
Original line number Diff line number Diff line
@@ -183,7 +183,7 @@ void __init anon_vma_init(void) 
 */

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;



	rcu_read_lock();
@@ -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);

	spin_lock(&anon_vma->lock);

	return anon_vma;

out:

	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) 
		if (!mapcount)

			break;

	}

	spin_unlock(&anon_vma->lock);



	page_unlock_anon_vma(anon_vma);

	return referenced;

}
@@ -802,7 +810,8 @@ static int try_to_unmap_anon(struct page *page, int migration) 
		if (ret == SWAP_FAIL || !page_mapped(page))

			break;

	}

	spin_unlock(&anon_vma->lock);



	page_unlock_anon_vma(anon_vma);

	return ret;

}