Commit 7f39dda9 authored Jun 04, 2014 by Hugh Dickins Committed by Linus Torvalds Jun 04, 2014

mm: fix sleeping function warning from __put_anon_vma



Trinity reports BUG:

  sleeping function called from invalid context at kernel/locking/rwsem.c:47
  in_atomic(): 0, irqs_disabled(): 0, pid: 5787, name: trinity-c27

__might_sleep < down_write < __put_anon_vma < page_get_anon_vma <
migrate_pages < compact_zone < compact_zone_order < try_to_compact_pages ..

Right, since conversion to mutex then rwsem, we should not put_anon_vma()
from inside an rcu_read_lock()ed section: fix the two places that did so.
And add might_sleep() to anon_vma_free(), as suggested by Peter Zijlstra.

Fixes: 88c22088 ("mm: optimize page_lock_anon_vma() fast-path")
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent f9625c48

mm/rmap.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -103,6 +103,7 @@ static inline void anon_vma_free(struct anon_vma *anon_vma)
		* LOCK should suffice since the actual taking of the lock must
		* happen _before_ what follows.
		*/
		might_sleep();
		if (rwsem_is_locked(&anon_vma->root->rwsem)) {
		anon_vma_lock_write(anon_vma);
		anon_vma_unlock_write(anon_vma);
		@@ -426,8 +427,9 @@ struct anon_vma page_get_anon_vma(struct page page)
		* above cannot corrupt).
		*/
		if (!page_mapped(page)) {
		rcu_read_unlock();
		put_anon_vma(anon_vma);
		anon_vma = NULL;
		return NULL;
		}
		out:
		rcu_read_unlock();
		@@ -477,9 +479,9 @@ struct anon_vma page_lock_anon_vma_read(struct page page)
		}

		if (!page_mapped(page)) {
		rcu_read_unlock();
		put_anon_vma(anon_vma);
		anon_vma = NULL;
		goto out;
		return NULL;
		}

		/* we pinned the anon_vma, its safe to sleep */