[PATCH] bcache: fix wrong BITMASK offset value for BDEV_CACHE_MODE

Lin Feng
2021-07-20T10:43:04Z

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@wangsu.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