[PATCH V3] bcache: revert replacing IS_ERR_OR_NULL with IS_ERR again

[liequan che]

Commit 028ddcac477b ("bcache: Remove unnecessary NULL point check in
node allocations") leads a NULL pointer deference in cache_set_flush().

1721         if (!IS_ERR_OR_NULL(c->root))
1722                 list_add(&c->root->list, &c->btree_cache);

>From the above code in cache_set_flush(), if previous registration code
fails before allocating c->root, it is possible c->root is NULL as what
it is initialized. Also __bch_btree_node_alloc() never returns NULL but
c->root is possible to be NULL at above line 1721.

This patch replaces IS_ERR() by IS_ERR_OR_NULL() to fix this.

Fixes: 028ddcac477b ("bcache: Remove unnecessary NULL point check in
node allocations")
Signed-off-by: Liequan Che <cheliequan@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Zheng Wang <zyytlz.wz@xxxxxxx>
Cc: Coly Li <colyli@xxxxxxx>
---
 drivers/md/bcache/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index e7abfdd77c3b..e42f1400cea9 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1718,7 +1718,7 @@ static CLOSURE_CALLBACK(cache_set_flush)
        if (!IS_ERR_OR_NULL(c->gc_thread))
                kthread_stop(c->gc_thread);

-       if (!IS_ERR(c->root))
+       if (!IS_ERR_OR_NULL(c->root))
                list_add(&c->root->list, &c->btree_cache);

        /*
--
2.46.0