Date: Sun, 9 Jan 2000 15:50:02 -0800 (PST) From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/15956: Off-by-1 error in diskstrategy() triggers bug in ATA Message-ID: <200001092350.PAA35697@freefall.freebsd.org>
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The following reply was made to PR kern/15956; it has been noted by GNATS.
From: Peter Jeremy <peter.jeremy@alcatel.com.au>
To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc: FreeBSD-gnats-submit@FreeBSD.ORG
Subject: Re: kern/15956: Off-by-1 error in diskstrategy() triggers bug in ATA
Date: Mon, 10 Jan 2000 10:39:40 +1100
On 2000-Jan-07 22:57:11 +1100, Poul-Henning Kamp <phk@critter.freebsd.dk> wrote:
>>- if (dscheck(bp, dp->d_slice) < 0) {
>>+ if (dscheck(bp, dp->d_slice) <= 0) {
...
>This was actually done that way deliberately, but not for any
>specific reason.
I wasn't sure about the reasons. What I did notice was that the other
references to dscheck() all do a <= check:
/sys/dev/ida/ida_disk.c:205: if (dscheck(bp, drv->slices) <= 0)
/sys/dev/vn/vn.c:305: if (vn->sc_slices != NULL && dscheck(bp, vn->sc_slices) <= 0) {
/sys/i386/isa/wd.c:581: if (dscheck(bp, du->dk_slices) <= 0)
/sys/i386/isa/wfd.c:419: if (dscheck(bp, t->dk_slices) <= 0) {
/sys/pc98/pc98/wd.c:675: if (dscheck(bp, du->dk_slices) <= 0)
Also, I can't see any point in passing zero-length I/O requests into
the low level drivers - bouncing them back out as quick as possible
will (if anything) improve performance.
I notice Soren has since added a (correct, unlike mine) patch to
the ata drivers to catch zero-length requests.
Peter
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