linux/kernel: introduce lower_48_bits function

Recent data integrity field enhancements allow reference tags to be up
to 48 bits. Introduce an inline helper function since this will be a
repeated operation.

Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220303201312.3255347-5-kbusch@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 33f47a9965132b9de89f7812a591574346869449..3877478681b98710929d1c7c186d2296e3470d7f 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -63,6 +63,15 @@
 }                                      \
 )
 
+/**
+ * lower_48_bits() - return bits 0-47 of a number
+ * @n: the number we're accessing
+ */
+static inline u64 lower_48_bits(u64 n)
+{
+       return n & ((1ull << 48) - 1);
+}
+
 /**
  * upper_32_bits - return bits 32-63 of a number
  * @n: the number we're accessing