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Subject[PATCH 3.12 116/181] mm: fix sleeping function warning from __put_anon_vma
Date
From: Hugh Dickins <hughd@google.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit 7f39dda9d86fb4f4f17af0de170decf125726f8c upstream.

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: 88c22088bf23 ("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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
mm/rmap.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 91ab22878103..4271107aa46e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -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 */
--
2.0.0


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