linux-kernel - [PATCH 2/2] panic fix for making cache device

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Date:   Tue, 25 Sep 2018 14:09:45 +0800
From:   Dongbo Cao <cdbdyx@....com>
To:     colyli@...e.de
Cc:     kent.overstreet@...il.com, linux-bcache@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dongbo Cao <cdbdyx@....com>
Subject: [PATCH 2/2] 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.

Signed-off-by: Dongbo Cao <cdbdyx@....com>
---
 drivers/md/bcache/super.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 0c0f6d8f..47d122ed 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -2036,7 +2036,12 @@ 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)) {
 		err = "ca->free[RESERVE_BTREE] alloc failed";
@@ -2102,6 +2107,7 @@ static int cache_alloc(struct cache *ca)
 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);
@@ -2131,6 +2137,8 @@ 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;
-- 
2.17.1