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Subject[PATCH 4.4 079/113] bcache: explicity type cast in bset_bkey_last()
From: Coly Li <>

[ Upstream commit 7c02b0055f774ed9afb6e1c7724f33bf148ffdc0 ]

In bset.h, macro bset_bkey_last() is defined as,
bkey_idx((struct bkey *) (i)->d, (i)->keys)

Parameter i can be variable type of data structure, the macro always
works once the type of struct i has member 'd' and 'keys'.

bset_bkey_last() is also used in macro csum_set() to calculate the
checksum of a on-disk data structure. When csum_set() is used to
calculate checksum of on-disk bcache super block, the parameter 'i'
data type is struct cache_sb_disk. Inside struct cache_sb_disk (also in
struct cache_sb) the member keys is __u16 type. But bkey_idx() expects
unsigned int (a 32bit width), so there is problem when sending
parameters via stack to call bkey_idx().

Sparse tool from Intel 0day kbuild system reports this incompatible
problem. bkey_idx() is part of user space API, so the simplest fix is
to cast the (i)->keys to unsigned int type in macro bset_bkey_last().

Reported-by: kbuild test robot <>
Signed-off-by: Coly Li <>
Signed-off-by: Jens Axboe <>
Signed-off-by: Sasha Levin <>
drivers/md/bcache/bset.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h
index b935839ab79c6..f483041eed986 100644
--- a/drivers/md/bcache/bset.h
+++ b/drivers/md/bcache/bset.h
@@ -380,7 +380,8 @@ void bch_btree_keys_stats(struct btree_keys *, struct bset_stats *);

/* Bkey utility code */

-#define bset_bkey_last(i) bkey_idx((struct bkey *) (i)->d, (i)->keys)
+#define bset_bkey_last(i) bkey_idx((struct bkey *) (i)->d, \
+ (unsigned int)(i)->keys)

static inline struct bkey *bset_bkey_idx(struct bset *i, unsigned idx)

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