rq_flag_bits and bio bi_rw flags

From: Matt Domsch
Date: Thu Aug 17 2006 - 18:25:40 EST


Jens, I'm hoping you can clear something up for me.

ll_rw_blk.c:
void blk_rq_bio_prep(request_queue_t *q, struct request *rq, struct
bio *bio)
{
/* first three bits are identical in rq->flags and bio->bi_rw
*/
rq->flags |= (bio->bi_rw & 7);

That was recently changed to be the first 2 bits not 3. But it made
me look.

/*
* bio bi_rw flags
*
* bit 0 -- read (not set) or write (set)
* bit 1 -- rw-ahead when set
* bit 2 -- barrier
* bit 3 -- fail fast, don't want low level driver retries
* bit 4 -- synchronous I/O hint: the block layer will unplug immediately
*/
#define BIO_RW 0
#define BIO_RW_AHEAD 1
#define BIO_RW_BARRIER 2
#define BIO_RW_FAILFAST 3
#define BIO_RW_SYNC 4


/*
* first three bits match BIO_RW* bits, important
*/
enum rq_flag_bits {
__REQ_RW, /* not set, read. set, write */
__REQ_FAILFAST, /* no low level driver retries */
__REQ_SORTED, /* elevator knows about this request
*/


The first bit matches. The second doesn't (BIO_RW_AHEAD vs
__REQ_FAILFAST). And obviously you just fixed the third bit.

Should BIO_RW_FAILFAST == __REQ_FAILFAST instead?

Thanks,
Matt

--
Matt Domsch
Software Architect
Dell Linux Solutions linux.dell.com & www.dell.com/linux
Linux on Dell mailing lists @ http://lists.us.dell.com
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