Date: Thu, 11 Mar 1999 11:03:04 -0500 (EST) From: "Mark J. Taylor" <mtaylor@cybernet.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: jkh@FreeBSD.ORG, msmith@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: Re: ccd driver problems with > 2GB segments, +fix Message-ID: <XFMail.990311110304.mtaylor@cybernet.com> In-Reply-To: <199903110751.XAA62027@apollo.backplane.com>
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The fixes actually came at two separate times: one to fix
the panic, and another to fix the filesystem.
1) Changing the long to u_long makes the ccd not panic the
system when it is configured. The corrected problem,
specifically, was that the "<< 9" of a 32 bit (signed)
word and subsequent store into a 32 bit (signed) word was
causing negative transfer sizes.
2) Using an off_f in read/write size comparisons corrected
the problem of putting a 64 bit value into a 32 bit word.
The second fix (the off_t) is really the only fix needed. The
first patch (the u_long) is not necessary: it hid the real
problem under most cases (32 bit << 9 being put into a 32 bit
value ends up being negative much of the time!), until the
math worked out "badly".
Here's the final and complete patch (for -current):
(this is exactly what NetBSD does, BTW)
*** ccd.c.orig Wed Mar 10 11:22:41 1999
--- ccd.c Thu Mar 11 10:53:13 1999
***************
*** 841,846 ****
--- 841,847 ----
register struct ccdcinfo *ci, *ci2 = NULL; /* XXX */
register struct ccdbuf *cbp;
register daddr_t cbn, cboff;
+ register off_t cbc;
#ifdef DEBUG
if (ccddebug & CCDB_IO)
***************
*** 919,929 ****
LIST_INIT(&cbp->cb_buf.b_dep);
cbp->cb_buf.b_resid = 0;
if (cs->sc_ileave == 0)
! cbp->cb_buf.b_bcount = dbtob(ci->ci_size - cbn);
else
! cbp->cb_buf.b_bcount = dbtob(cs->sc_ileave - cboff);
! if (cbp->cb_buf.b_bcount > bcount)
! cbp->cb_buf.b_bcount = bcount;
cbp->cb_buf.b_bufsize = cbp->cb_buf.b_bcount;
--- 920,929 ----
LIST_INIT(&cbp->cb_buf.b_dep);
cbp->cb_buf.b_resid = 0;
if (cs->sc_ileave == 0)
! cbc = dbtob((off_t)(ci->ci_size - cbn));
else
! cbc = dbtob((off_t)(cs->sc_ileave - cboff));
! cbp->cb_buf.b_bcount = (cbc < bcount) ? cbc : bcount;
cbp->cb_buf.b_bufsize = cbp->cb_buf.b_bcount;
On 11-Mar-99 Matthew Dillon wrote:
> Interesting. What if each disk is 8GB and we set the stripe
> size to 8GB? Won't that break the u_long ( i.e. was broken
> before, and is still broken now ). Perhaps these variables
> should be 64 bit quantities throughout except for the
> bp->b_count?
>
> -Matt
> Matthew Dillon
> <dillon@backplane.com>
>
>:Fix:
>:The ccd driver has a variable "bcount" that is a long: it needs
>:to be a u_long. And, a 64 bit int is shifted into a 32 bit int
>:in ccdbuffer(): the 32 bit int must changed to be a 64 bit int.
>:
>:This second change has already been made in NetBSD (somebody else
>:figured it out), where the ccd driver originated from. It was
>:rather tricky to find: the math involving block numbers and ccd
>:...
--------------------------------------------------------------------
Mark J. Taylor Networking Research
Cybernet Systems mtaylor@cybernet.com
727 Airport Blvd. PHONE (734) 668-2567
Ann Arbor, MI 48108 FAX (734) 668-8780
http://www.cybernet.com/ http://www.netmax.com/
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