[PATCH] bcache: Make sure to pass GFP_WAIT to mempool_alloc()

[Gabriel de Perthuis <g2p.code@gmail.com>]

this was very wrong - mempool_alloc() only guarantees success with GFP_WAIT.
bcache uses GFP_NOWAIT in various other places where we have a fallback,
circuits must've gotten crossed when writing this code or something.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
---

The bug was introduced in v3.11, fixed in v3.17.

Jens mentioned bcache has many stable@ candidates previously: 
https://lkml.org/lkml/2014/9/5/360

I'm cherry-picking this fix because I was getting crashes.

---
  drivers/md/bcache/btree.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 9dd9f1c..e538d45 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -200,11 +200,11 @@ void bch_btree_node_read_done(struct btree *b)
  {
  	const char *err = "bad btree header";
  	struct bset *i = btree_bset_first(b);
  	struct btree_iter *iter;
-	iter = mempool_alloc(b->c->fill_iter, GFP_NOWAIT);
+	iter = mempool_alloc(b->c->fill_iter, GFP_NOIO);
  	iter->size = b->c->sb.bucket_size / b->c->sb.block_size;
  	iter->used = 0;
   #ifdef CONFIG_BCACHE_DEBUG
  	iter->b = &b->keys;
-- 
2.2.0.71.g3365589