According to the comment in blk_rq_io_prep(), about line 2030 of blk-core.c: /* first two bits are identical in rq->cmd_flags and bio->bi_rw */ rq->cmd_flags |= (bio->bi_rw & 3); Is this true? These are the bits in bi_rw: #define BIO_RW 0 #define BIO_RW_AHEAD 1 #define BIO_RW_BARRIER 2 #define BIO_RW_FAILFAST 3 #define BIO_RW_SYNC 4 #define BIO_RW_META 5 And these are the (first) bits in rq->cmd_flags: __REQ_RW, /* not set, read. set, write */ __REQ_FAILFAST, /* no low level driver retries */ __REQ_SORTED, /* elevator knows about this request */ __REQ_SOFTBARRIER, /* may not be passed by ioscheduler */ __REQ_HARDBARRIER, /* may not be passed by drive either */ __REQ_FUA, /* forced unit access */ Are we intending that BIO_RW_AHEAD maps to REQ_FAILFAST? When I started composing this mail I was just going to call it a lie -- but now I think about it, it makes a certain amount of sense. The comment really ought to be a little more explicit though, if that's the case. That's not _identical_, even if it's intentional. In blk_alloc_request() we have an even more interesting claim -- this time it's _three_ bits which are identical: /* * first three bits are identical in rq->cmd_flags and bio->bi_rw, * see bio.h and blkdev.h */ rq->cmd_flags = rw | REQ_ALLOCED; AFAICT the only thing passed in via the 'rw' variable is the R/W bit and maybe REQ_RW_SYNC when it's called from get_request(), so the comment doesn't matter and can just be removed, I think? -- dwmw2 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
