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authorOleg Nesterov <oleg@tv-sign.ru>2007-02-28 20:13:49 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-03-01 14:53:39 -0800
commit34bbd704051c9d053d69e90569a3a2365f4c7b50 (patch)
treef5fb6f3941cd09be0fb92ae80f9759ad64fca709
parent48dba8ab9b93c3b6b57946bd45ae013402b0b054 (diff)
[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: Oleg 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: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/rmap.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 669acb22b57..22ed3f71a67 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -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;
}