[PATCH] adapt page_lock_anon_vma() to PREEMPT_RCU (34bbd704) · Commits · 戴 / test

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>

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;
		}

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