On Sun, Apr 07, 2019 at 05:35:45PM +0300, Alex Lyakas wrote:
> Hi Christoph,
>
> I understand and agree with your concern.
>
> Looking at the code, bi_flags is 16-bits wide, and only top 3 bits are
> preserved by bio_reset(). These bits are used to indicate a bvec pool.
> So we don't have any free bits to move the BIO_REFFED to. Unless we
> make bi_flags wider.
I think we just need to move BIO_REFFED around. Something like the
untested patch below should do the job, although blk_types.h could
use some additional cleanup in this area..
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index be418275763c..017a450dc8e0 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -224,13 +224,13 @@ enum {
BIO_NULL_MAPPED, /* contains invalid user pages */
BIO_QUIET, /* Make BIO Quiet */
BIO_CHAIN, /* chained bio, ->bi_remaining in effect */
- BIO_REFFED, /* bio has elevated ->bi_cnt */
BIO_THROTTLED, /* This bio has already been subjected to
* throttling rules. Don't do it again. */
BIO_TRACE_COMPLETION, /* bio_endio() should trace the final completion
* of this bio. */
BIO_QUEUE_ENTERED, /* can use blk_queue_enter_live() */
BIO_TRACKED, /* set if bio goes through the rq_qos path */
+ BIO_REFFED, /* bio has elevated ->bi_cnt */
BIO_FLAG_LAST
};
@@ -257,9 +257,9 @@ enum {
/*
* Flags starting here get preserved by bio_reset() - this includes
- * only BVEC_POOL_IDX()
+ * BVEC_POOL_IDX()
*/
-#define BIO_RESET_BITS BVEC_POOL_OFFSET
+#define BIO_RESET_BITS BIO_REFFED
typedef __u32 __bitwise blk_mq_req_flags_t;
