block: better op and flags encoding

Now that we don't need the common flags to overflow outside the range
of a 32-bit type we can encode them the same way for both the bio and
request fields.  This in addition allows us to place the operation
first (and make some room for more ops while we're at it) and to
stop having to shift around the operation values.

In addition this allows passing around only one value in the block layer
instead of two (and eventuall also in the file systems, but we can do
that later) and thus clean up a lot of code.

Last but not least this allows decreasing the size of the cmd_flags
field in struct request to 32-bits.  Various functions passing this
value could also be updated, but I'd like to avoid the churn for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 37 insertions, 46 deletions

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index ec69a8f..dca972d 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -88,24 +88,6 @@ struct bio {
 	struct bio_vec		bi_inline_vecs[0];
 };
 
-#define BIO_OP_SHIFT	(8 * FIELD_SIZEOF(struct bio, bi_opf) - REQ_OP_BITS)
-#define bio_flags(bio)	((bio)->bi_opf & ((1 << BIO_OP_SHIFT) - 1))
-#define bio_op(bio)	((bio)->bi_opf >> BIO_OP_SHIFT)
-
-#define bio_set_op_attrs(bio, op, op_flags) do {			\
-	if (__builtin_constant_p(op))					\
-		BUILD_BUG_ON((op) + 0U >= (1U << REQ_OP_BITS));		\
-	else								\
-		WARN_ON_ONCE((op) + 0U >= (1U << REQ_OP_BITS));		\
-	if (__builtin_constant_p(op_flags))				\
-		BUILD_BUG_ON((op_flags) + 0U >= (1U << BIO_OP_SHIFT));	\
-	else								\
-		WARN_ON_ONCE((op_flags) + 0U >= (1U << BIO_OP_SHIFT));	\
-	(bio)->bi_opf = bio_flags(bio);					\
-	(bio)->bi_opf |= (((op) + 0U) << BIO_OP_SHIFT);			\
-	(bio)->bi_opf |= (op_flags);					\
-} while (0)
-
 #define BIO_RESET_BYTES		offsetof(struct bio, bi_max_vecs)
 
 /*
@@ -147,26 +129,40 @@ struct bio {
 #endif /* CONFIG_BLOCK */
 
 /*
- * Request flags.  For use in the cmd_flags field of struct request, and in
- * bi_opf of struct bio.  Note that some flags are only valid in either one.
+ * Operations and flags common to the bio and request structures.
+ * We use 8 bits for encoding the operation, and the remaining 24 for flags.
  */
-enum rq_flag_bits {
-	/* common flags */
-	__REQ_FAILFAST_DEV,	/* no driver retries of device errors */
+#define REQ_OP_BITS	8
+#define REQ_OP_MASK	((1 << REQ_OP_BITS) - 1)
+#define REQ_FLAG_BITS	24
+
+enum req_opf {
+	REQ_OP_READ,
+	REQ_OP_WRITE,
+	REQ_OP_DISCARD,		/* request to discard sectors */
+	REQ_OP_SECURE_ERASE,	/* request to securely erase sectors */
+	REQ_OP_WRITE_SAME,	/* write same block many times */
+	REQ_OP_FLUSH,		/* request for cache flush */
+	REQ_OP_ZONE_REPORT,	/* Get zone information */
+	REQ_OP_ZONE_RESET,	/* Reset a zone write pointer */
+
+	REQ_OP_LAST,
+};
+
+enum req_flag_bits {
+	__REQ_FAILFAST_DEV =	/* no driver retries of device errors */
+		REQ_OP_BITS,
 	__REQ_FAILFAST_TRANSPORT, /* no driver retries of transport errors */
 	__REQ_FAILFAST_DRIVER,	/* no driver retries of driver errors */
-
 	__REQ_SYNC,		/* request is sync (sync write or read) */
 	__REQ_META,		/* metadata io request */
 	__REQ_PRIO,		/* boost priority in cfq */
-
 	__REQ_NOMERGE,		/* don't touch this for merging */
 	__REQ_NOIDLE,		/* don't anticipate more IO after this one */
 	__REQ_INTEGRITY,	/* I/O includes block integrity payload */
 	__REQ_FUA,		/* forced unit access */
 	__REQ_PREFLUSH,		/* request for cache flush */
 	__REQ_RAHEAD,		/* read ahead, can fail anytime */
-
 	__REQ_NR_BITS,		/* stops here */
 };
 
@@ -176,37 +172,32 @@ enum rq_flag_bits {
 #define REQ_SYNC		(1ULL << __REQ_SYNC)
 #define REQ_META		(1ULL << __REQ_META)
 #define REQ_PRIO		(1ULL << __REQ_PRIO)
+#define REQ_NOMERGE		(1ULL << __REQ_NOMERGE)
 #define REQ_NOIDLE		(1ULL << __REQ_NOIDLE)
 #define REQ_INTEGRITY		(1ULL << __REQ_INTEGRITY)
+#define REQ_FUA			(1ULL << __REQ_FUA)
+#define REQ_PREFLUSH		(1ULL << __REQ_PREFLUSH)
+#define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
 
 #define REQ_FAILFAST_MASK \
 	(REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)
-#define REQ_COMMON_MASK \
-	(REQ_FAILFAST_MASK | REQ_SYNC | REQ_META | REQ_PRIO | REQ_NOIDLE | \
-	 REQ_PREFLUSH | REQ_FUA | REQ_INTEGRITY | REQ_NOMERGE | REQ_RAHEAD)
-#define REQ_CLONE_MASK		REQ_COMMON_MASK
 
-/* This mask is used for both bio and request merge checking */
 #define REQ_NOMERGE_FLAGS \
 	(REQ_NOMERGE | REQ_PREFLUSH | REQ_FUA)
 
-#define REQ_RAHEAD		(1ULL << __REQ_RAHEAD)
-#define REQ_FUA			(1ULL << __REQ_FUA)
-#define REQ_NOMERGE		(1ULL << __REQ_NOMERGE)
-#define REQ_PREFLUSH		(1ULL << __REQ_PREFLUSH)
+#define bio_op(bio) \
+	((bio)->bi_opf & REQ_OP_MASK)
+#define req_op(req) \
+	((req)->cmd_flags & REQ_OP_MASK)
 
-enum req_op {
-	REQ_OP_READ,
-	REQ_OP_WRITE,
-	REQ_OP_DISCARD,		/* request to discard sectors */
-	REQ_OP_SECURE_ERASE,	/* request to securely erase sectors */
-	REQ_OP_WRITE_SAME,	/* write same block many times */
-	REQ_OP_FLUSH,		/* request for cache flush */
-	REQ_OP_ZONE_REPORT,	/* Get zone information */
-	REQ_OP_ZONE_RESET,	/* Reset a zone write pointer */
-};
+/* obsolete, don't use in new code */
+#define bio_set_op_attrs(bio, op, op_flags) \
+	((bio)->bi_opf |= (op | op_flags))
 
-#define REQ_OP_BITS 3
+static inline bool op_is_sync(unsigned int op)
+{
+	return (op & REQ_OP_MASK) == REQ_OP_READ || (op & REQ_SYNC);
+}
 
 typedef unsigned int blk_qc_t;
 #define BLK_QC_T_NONE	-1U