[PATCH 2/2] mtd: ubi: use GFP_NOIO for lock tree entry allocation

[Yelin Fei]

From: Ye Linfei <yelinfei at ruijie.com.cn>

The per-LEB lock tree entry can be allocated while UBI is executing on
behalf of a synchronous block-layer consumer (ubiblock), where issuing
further block I/O from direct reclaim would deadlock; see the
preceding commit "mtd: ubi: block: forbid direct reclaim I/O during
synchronous read" for the full analysis.

Make the allocation self-contained: GFP_NOIO restricts direct reclaim
to dropping clean page cache and shrinking slabs, page (swap) reclaim
is left to kswapd, and the worst case is -ENOMEM, which callers
already propagate as an ordinary recoverable I/O error.

memalloc_noio_save()/memalloc_noio_restore() in ubiblock_read()
already enforce this for the whole read scope; keeping the allocation
here self-contained as well means the safety property does not depend
on every future caller remembering to set up that scope.

Signed-off-by: Ye Linfei <yelinfei at ruijie.com.cn>
---
 drivers/mtd/ubi/eba.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index f0c549e62c55..8fe68e7fff58 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -247,7 +247,7 @@ static struct ubi_ltree_entry *ltree_add_entry(struct ubi_device *ubi,
 {
 	struct ubi_ltree_entry *le, *le1, *le_free;
 
-	le = kmalloc_obj(struct ubi_ltree_entry, GFP_NOFS);
+	le = kmalloc_obj(struct ubi_ltree_entry, GFP_NOIO); /* see ubiblock_read() */
 	if (!le)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.25.1