[PATCH v3] block: add NULL checks for bic in bfq_bfqq_save_state function

[yanlonglong <yanlonglong@kylinos.cn>]

When the `bic` variable is null, referencing `bfqq_data` through `bic` will
cause the program to crash. Therefore, the null check for `bic` should be
moved to the beginning of the function to prevent referencing a null pointer.

Fixes:fd571df0ac5b("block, bfq: turn bfqq_data into an array in bfq_io_cq")
Signed-off-by: yanlonglong <yanlonglong@kylinos.cn>
---
 block/bfq-iosched.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 141c602d5e85..c8cf8764d48d 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -3036,7 +3036,7 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
 {
 	struct bfq_io_cq *bic = bfqq->bic;
 	unsigned int a_idx = bfqq->actuator_idx;
-	struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[a_idx];
+	struct bfq_iocq_bfqq_data *bfqq_data = NULL;
 
 	/*
 	 * If !bfqq->bic, the queue is already shared or its requests
@@ -3046,6 +3046,7 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
 	if (!bic)
 		return;
 
+	bfqq_data = &bic->bfqq_data[a_idx];
 	bfqq_data->saved_last_serv_time_ns = bfqq->last_serv_time_ns;
 	bfqq_data->saved_inject_limit =	bfqq->inject_limit;
 	bfqq_data->saved_decrease_time_jif = bfqq->decrease_time_jif;
-- 
2.43.0