Date: Thu, 14 Mar 2002 17:47:36 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Mike Silbersack <silby@silby.com> Cc: Terry Lambert <tlambert2@mindspring.com>, "Clark C . Evans" <cce@clarkevans.com>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: panic: pmap_enter Message-ID: <200203150147.g2F1laf50765@apollo.backplane.com> References: <20020314070732.H23489-100000@patrocles.silby.com>
next in thread | previous in thread | raw e-mail | index | archive | help
:On Tue, 12 Mar 2002, Terry Lambert wrote:
:
:> #define blkmap(fs, map, loc) \
:> (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
:>
:> looks a little suspect, doesn't it? "& 0" for 8 is probably
:> correct, but "& 1" for 4 and "& 2" for 2 and "& 4" for 1 is
:> probably not right... maybe:
:>
:> #define blkmap(fs, map, loc) \
:> (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & 0xff & ((0xff >> (NBBY -
:> (fs)->fs_frag))^0xff))
:>
:> Would be more right? After all, it's the high bits of the low
:> bits you want to save, not the low bits of the low bits...
:>
:> -- Terry
:
:FWIW, I didn't mean to ignore this message, I was going to look it over
:carefully before commenting. However, Sid Meier told me that I needed to
:spend some time taking over the world, so I was unable to.
:
:If anyone familiar with FFS wants to check it out, please be my guest,
:otherwise I'll try to get to it soon.
:
:Mike "Silby" Silbersack
That doesn't look like '& 0' for 8 to me. NBBY is 8,
fs_frag of 8, results in 0xFF >> 0 which is 0xFF, not 0.
The original code looks correct. Try this:
-Matt
Matthew Dillon
<dillon@backplane.com>
/*
* BLKMAP.C
*
* #define blkmap(fs, map, loc) \
(((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
*
* bno = block number (in fragment-sized blocks)
* frag = fragment ratio N:1
*
*/
#include <stdio.h>
#define NBBY 8
int
main(int ac, char **av)
{
int bno;
for (bno = 0; bno < 32; ++bno) {
int frag;
if ((bno & 15) == 0)
printf("BLOCK\t8:1\t\t\t4:1\t\t\t2:1\t\t\t1:1\n");
printf("%5d", bno);
for (frag = 8; frag >= 1; frag >>= 1) {
printf("\t([%d] >> %d) & 0x%02x",
bno / NBBY,
bno % NBBY,
0xFF >> (NBBY - frag)
);
}
printf("\n");
}
return(0);
}
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200203150147.g2F1laf50765>