Hi Boris, On Fri, 1 Feb 2008 08:51:17 +0100, Borislav Petkov wrote: > > > > The below fix should be enough. It's perfectly legal to have leftover > > > > byte counts when the drive signals completion, happens all the time for > > > > eg user issued commands where you don't know an exact byte count. > > > > > > Actually, this behavior has been the case even before > > > the __blk_end_request() changes. > > > I did test plain 2.6.24 with the following > > > > > > > > > --- linux-2.6/drivers/ide/ide-cd.c 2008-01-31 22:18:59.000000000 +0100 > > > +++ linux-2.6/drivers/ide/ide-cd.c-new 2008-01-31 22:18:50.000000000 +0100 > > > @@ -1711,8 +1711,12 @@ static ide_startstop_t cdrom_newpc_intr( > > > /* > > > * If DRQ is clear, the command has completed. > > > */ > > > - if ((stat & DRQ_STAT) == 0) > > > + if ((stat & DRQ_STAT) == 0) { > > > + blk_dump_rq_flags(rq, "ide-cd: rq still having bio"); > > > + printk("backup: data_len=%u bi_size=%u\n", > > > + rq->data_len, rq->bio->bi_size); > > > goto end_request; > > > + } > > > > > > /* > > > * check which way to transfer data > > > > > > > > > to see whether we've been getting residual byte counts: > > > > > > Jan 31 22:10:06 gollum kernel: [ 26.702877] ide-cd: rq still having bio: dev hdc: type=2, flags=114c8 > > > Jan 31 22:10:06 gollum kernel: [ 26.702945] > > > Jan 31 22:10:06 gollum kernel: [ 26.702946] sector 2673511, nr/cnr 0/0 > > > Jan 31 22:10:06 gollum kernel: [ 26.703052] bio dfa8ec40, biotail dfa8ec40, buffer 00000000, data 00000000, len 158 > > > Jan 31 22:10:06 gollum kernel: [ 26.703122] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00 > > > Jan 31 22:10:06 gollum kernel: [ 26.703877] backup: data_len=158 bi_size=158 > > > > > > ... so we've been simply silently ignoring this until now so > > > i guess we don't need to BUG() for something that's totally benign. > > Hi Kiyoshi, > > > end_that_request_last() is not called when __blk_end_reuqest() > > returns 1. Then, the issuer isn't waken up. > > So I think the BUG() or error messages should be there. > > you mean, end_that_request_last() isn't called when __end_that_request_first() > returns an error and this is the case only for fs and pc requests. > Otherwise it _is_ called, thus simulating somewhat the previous behavior. > However, we never BUG()'ged on residual byte counts before and > this driver has been in the kernel tree for ages, so what puzzles > me now is how is BUG()'ing here better than before and shouldn't we > simply issue a warning instead of killing the interrupt handler... The Jens' patch passes the residual byte counts to __blk_end_request(), so __end_that_reqeust_first() should never return 1 and we should never BUG() on the residual byte counts, unless inconsistency happens such as the size of remaining bios is bigger than the residual byte counts. So if __blk_end_request() returns 1 even with the Jens' patch, it means that the block layer or the driver really have a bug. And then, the request and the bios could leak or the issuer would wait forever because end_that_request_last() isn't called. The previous behavior might ignore such inconsistency and leak only the bios because it was calling end_that_request_last() anyway. I would like to BUG() in such cases personally, but I don't object strongly if you prefer not to BUG(). Thanks, Kiyoshi Ueda - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html