Messages in this thread Patch in this message |  | | | Date | Fri, 1 Feb 2008 19:29:09 +0100 | | Subject | Re: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 && -g8561b089 | | From | Borislav Petkov <> |
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On Fri, Feb 01, 2008 at 12:39:27PM -0500, Kiyoshi Ueda wrote:
<snip>
> > > 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.
yep.
> 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().
BUG() is definitely what we should do here to catch this case of sizeof(bios) > rq->data_len. Putting a brown paper bag over the issue will never get it fixed if it really leaks bios. Thanks for clarifying that.
By the way, shouldn't we be doing a little branch prediction here:
diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c index 74c6087..bee05a3 100644 --- a/drivers/ide/ide-cd.c +++ b/drivers/ide/ide-cd.c @@ -1722,7 +1722,7 @@ static ide_startstop_t cdrom_newpc_intr(ide_drive_t *drive) */ if ((stat & DRQ_STAT) == 0) { spin_lock_irqsave(&ide_lock, flags); - if (__blk_end_request(rq, 0, 0)) + if (unlikely(__blk_end_request(rq, 0, rq->data_len))) BUG(); HWGROUP(drive)->rq = NULL; spin_unlock_irqrestore(&ide_lock, flags);
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