@@ -29,7 +29,7 @@ struct bio {
* top bits REQ_OP. Use
* accessors.
*/
- unsigned short bi_flags; /* status, command, etc */
+ unsigned short bi_flags; /* status, etc and bvec pool number */
unsigned short bi_ioprio;
struct bvec_iter bi_iter;
@@ -102,12 +102,7 @@ struct bio {
#define BIO_REFFED 8 /* bio has elevated ->bi_cnt */
#define BIO_THROTTLED 9 /* This bio has already been subjected to
* throttling rules. Don't do it again. */
-
-/*
- * Flags starting here get preserved by bio_reset() - this includes
- * BVEC_POOL_IDX()
- */
-#define BIO_RESET_BITS 10
+/* See BVEC_POOL_OFFSET below before adding new flags */
/*
* We support 6 different bvec pools, the last one is magic in that it
@@ -117,13 +112,22 @@ struct bio {
#define BVEC_POOL_MAX (BVEC_POOL_NR - 1)
/*
- * Top 4 bits of bio flags indicate the pool the bvecs came from. We add
+ * Top 3 bits of bio flags indicate the pool the bvecs came from. We add
* 1 to the actual index so that 0 indicates that there are no bvecs to be
* freed.
*/
-#define BVEC_POOL_BITS (4)
+#define BVEC_POOL_BITS (3)
#define BVEC_POOL_OFFSET (16 - BVEC_POOL_BITS)
#define BVEC_POOL_IDX(bio) ((bio)->bi_flags >> BVEC_POOL_OFFSET)
+#if (1<< BVEC_POOL_BITS) < (BVEC_POOL_NR+1)
+# error "BVEC_POOL_BITS is too small"
+#endif
+
+/*
+ * Flags starting here get preserved by bio_reset() - this includes
+ * only BVEC_POOL_IDX()
+ */
+#define BIO_RESET_BITS BVEC_POOL_OFFSET
/*
* Operations and flags common to the bio and request structures.
The comment for the 'flags' field of 'bio' mentions "command" which is no longer stored there, and doesn't mention the bvec pool number, which is. BIO_RESET_BITS is set in such a way that it would need to be updated if new bits were added, which is easy to miss. BVEC_POOL_BITS is larger than needed. The BVEC_POOL_IDX() ranges from 0 to 6, so 3 bits are sufficient. This patch make improvements in each of these areas. Signed-off-by: NeilBrown <neilb@suse.com> --- include/linux/blk_types.h | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-)