[PATCH] bcache: add a check for the return of kzalloc()

[xkernel.wang@foxmail.com]

From: Xiaoke Wang <xkernel.wang@foxmail.com>

kzalloc() is a memory allocation function which can return NULL when
some internal memory errors happen. So it is better to check it to
prevent potential wrong memory access.

Signed-off-by: Xiaoke Wang <xkernel.wang@foxmail.com>
---
Note: I just roughly handled the error and this seems to affect the
original functionality. If this cannot fail, maybe the tag
`__GFP_NOFAIL` should be considered.
 drivers/md/bcache/request.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 6d1de88..1dc9821 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1107,14 +1107,16 @@ static void detached_dev_do_request(struct bcache_device *d, struct bio *bio,
 	 * which would call closure_get(&dc->disk.cl)
 	 */
 	ddip = kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO);
-	ddip->d = d;
-	/* Count on the bcache device */
-	ddip->orig_bdev = orig_bdev;
-	ddip->start_time = start_time;
-	ddip->bi_end_io = bio->bi_end_io;
-	ddip->bi_private = bio->bi_private;
-	bio->bi_end_io = detached_dev_end_io;
-	bio->bi_private = ddip;
+	if (ddip) {
+		ddip->d = d;
+		/* Count on the bcache device */
+		ddip->orig_bdev = orig_bdev;
+		ddip->start_time = start_time;
+		ddip->bi_end_io = bio->bi_end_io;
+		ddip->bi_private = bio->bi_private;
+		bio->bi_end_io = detached_dev_end_io;
+		bio->bi_private = ddip;
+	}
 
 	if ((bio_op(bio) == REQ_OP_DISCARD) &&
 	    !blk_queue_discard(bdev_get_queue(dc->bdev)))
--