bcache: panic fix for making cache device

when the nbuckets of cache device is smaller than 1024, making cache
device will trigger BUG_ON in kernel, add a condition to avoid this.

Reported-by: nitroxis <n@nxs.re>
Signed-off-by: Dongbo Cao <cdbdyx@163.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 4e89d6d4bbd6be74bab398d518d9cdf40ca2a878..7bbd670a5a84841206405cbb1ff397abb72f412b 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2071,6 +2071,11 @@ static int cache_alloc(struct cache *ca)
         */
        btree_buckets = ca->sb.njournal_buckets ?: 8;
        free = roundup_pow_of_two(ca->sb.nbuckets) >> 10;
+       if (!free) {
+               ret = -EPERM;
+               err = "ca->sb.nbuckets is too small";
+               goto err_free;
+       }
 
        if (!init_fifo(&ca->free[RESERVE_BTREE], btree_buckets,
                                                GFP_KERNEL)) {
@@ -2148,6 +2153,7 @@ err_movinggc_alloc:
 err_prio_alloc:
        free_fifo(&ca->free[RESERVE_BTREE]);
 err_btree_alloc:
+err_free:
        module_put(THIS_MODULE);
        if (err)
                pr_notice("error %s: %s", ca->cache_dev_name, err);
@@ -2177,6 +2183,8 @@ static int register_cache(struct cache_sb *sb, struct page *sb_page,
                blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
                if (ret == -ENOMEM)
                        err = "cache_alloc(): -ENOMEM";
+               else if (ret == -EPERM)
+                       err = "cache_alloc(): cache device is too small";
                else
                        err = "cache_alloc(): unknown error";
                goto err;