Date: Mon, 23 Oct 2000 22:14:50 -0400 From: "John W. De Boskey" <jwd@bsdwins.com> To: Bruce Evans <bde@zeta.org.au> Cc: Tor.Egge@fast.no, jwd@FreeBSD.ORG, freebsd-current@FreeBSD.ORG, peter@FreeBSD.ORG Subject: Re: newfs/fsck problem (bad superblocks) Message-ID: <20001023221450.A46780@bsdwins.com> In-Reply-To: <Pine.BSF.4.21.0010241241280.2027-100000@besplex.bde.org>; from bde@zeta.org.au on Tue, Oct 24, 2000 at 12:54:29PM %2B1100 References: <200010220822.KAA59278@midten.fast.no> <Pine.BSF.4.21.0010241241280.2027-100000@besplex.bde.org>
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See below..
----- Bruce Evans's Original Message -----
> On Sun, 22 Oct 2000 Tor.Egge@fast.no wrote:
>
> > > Reverting src/sbin/newfs/mkfs.c to revision 1.29 fixes
> > > the problem.
> > >
> > > With just a quick review of the patch, I'm not sure I
> > > understand what forces the last dirty buffer to be
> > > written.
>
> This worried me too.
>
> > Try the enclosed patch. It flushes the dirty buffer before
> > program exit and before reading blocks.
>
> There are still some serious (?) overflow bugs.
>
> Index: mkfs.c
> ===================================================================
> RCS file: /home/ncvs/src/sbin/newfs/mkfs.c,v
> retrieving revision 1.29
> retrieving revision 1.30
> diff -c -2 -r1.29 -r1.30
> *** mkfs.c 1999/08/28 00:13:50 1.29
> --- mkfs.c 2000/10/17 00:41:36 1.30
> ...
> ***************
> *** 1341,1344 ****
> --- 1347,1381 ----
> }
> if (Nflag)
> + return;
> + done = 0;
> + if (wc_end == 0 && size <= WCSIZE) {
> + wc_sect = bno;
> + bcopy(bf, wc, size);
> + wc_end = size;
> + if (wc_end < WCSIZE)
> + return;
> + done = 1;
> + }
> + if (wc_sect * sectorsize + wc_end == bno * sectorsize &&
> ^ overflow ^ overflow
I agree it's an overflow, and I'll get a patch in for it. But
from a lucky point of view, since the overflow occurs on both sides
of the test, it's a serendipidoues match which doesn't hurt, or
the match fails, which causes the cache to flush.
> + wc_end + size <= WCSIZE) {
> + bcopy(bf, wc + wc_end, size);
> + wc_end += size;
> + if (wc_end < WCSIZE)
> + return;
> + done = 1;
> + }
> + if (wc_end) {
> + if (lseek(fso, (off_t)wc_sect * sectorsize, SEEK_SET) < 0) {
> ^^^^^^^ must cast like this to prevent overflow
Well, the above can overflow, but the probability of it overflowing
when things are working correctly approaches zero :-)
Regardless, we could put in a test to make sure the final offset
computed is valid.
-john
> + printf("seek error: %ld\n", (long)wc_sect);
> + err(35, "wtfs - writecombine");
> + }
> + n = write(fso, wc, wc_end);
> + if (n != wc_end) {
> + printf("write error: %ld\n", (long)wc_sect);
> + err(36, "wtfs - writecombine");
> + }
> + wc_end = 0;
> + }
> + if (done)
> return;
> if (lseek(fso, (off_t)bno * sectorsize, SEEK_SET) < 0) {
>
> Bruce
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