linux-kernel - [PATCH] bcache: fix wrong BITMASK offset value for BDEV_CACHE

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Message-Id: <20210720103246.112027-1-linf@wangsu.com>
Date:   Tue, 20 Jul 2021 18:32:46 +0800
From:   Lin Feng <linf@...gsu.com>
To:     colyli@...e.de
Cc:     axboe@...nel.dk, linf@...gsu.com, linux-kernel@...r.kernel.org,
        linux-bcache@...r.kernel.org
Subject: [PATCH] bcache: fix wrong BITMASK offset value for BDEV_CACHE_MODE

Original codes:
BITMASK(CACHE_SYNC,			struct cache_sb, flags, 0, 1);
BITMASK(CACHE_DISCARD,			struct cache_sb, flags, 1, 1);
BITMASK(CACHE_REPLACEMENT,		struct cache_sb, flags, 2, 3);
...
BITMASK(BDEV_CACHE_MODE,		struct cache_sb, flags, 0, 4);

Should BDEV_CACHE_MODE bits start from bit-nr 5(2+3) else it overlaps
with previous defined bit chunks, since we have 4 types of cache modes,
BDEV_CACHE_MODE will overwrite CACHE_SYNC and CACHE_DISCARD bits.

This bug stays there since first upstream version of bcache, don't know
why it lives so long, or am i missing something, please point me out
if I'm wrong, thanks!

Signed-off-by: Lin Feng <linf@...gsu.com>
---
 include/uapi/linux/bcache.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h
index cf7399f03b71..dccd89756451 100644
--- a/include/uapi/linux/bcache.h
+++ b/include/uapi/linux/bcache.h
@@ -288,7 +288,7 @@ BITMASK(CACHE_REPLACEMENT,		struct cache_sb, flags, 2, 3);
 #define CACHE_REPLACEMENT_FIFO		1U
 #define CACHE_REPLACEMENT_RANDOM	2U
 
-BITMASK(BDEV_CACHE_MODE,		struct cache_sb, flags, 0, 4);
+BITMASK(BDEV_CACHE_MODE,		struct cache_sb, flags, 5, 4);
 #define CACHE_MODE_WRITETHROUGH		0U
 #define CACHE_MODE_WRITEBACK		1U
 #define CACHE_MODE_WRITEAROUND		2U
-- 
2.31.1