Date: Sat, 15 Jan 2000 02:09:49 -0500 (EST) From: "Mark W. Krentel" <krentel@dreamscape.com> To: freebsd-stable@freebsd.org Subject: fstat's use of device numbers Message-ID: <200001150709.CAA11205@dreamscape.com>
next in thread | raw e-mail | index | archive | help
I have a question about fstat's treatment of the high-order bits in a
device's minor number. My /etc/fstab includes:
# Device Mountpoint FStype Options Dump Pass
/dev/da0s2f /usr ufs rw 2 2
/dev/da0s3f /home ufs rw 2 2
That is, /usr and /home are both the "f" partition on different slices
of the same disk. As a result, these two partitions are confused by
fstat(1) with the -f flag (restrict to open files on the same file
system as the -f argument).
% fstat -f /home
USER CMD PID FD MOUNT INUM MODE SZ|DV R/W
krentel fstat 10702 wd /home 315401 drwxr-xr-x 2048 r
krentel fstat 10702 text /usr 7946 -r-xr-sr-x 10160 r
...
That is, I asked for files on /home, but I also got /usr, a separate
partition. In general, this will happen whenever there are two
partitions with the same letter on different slices of the same disk.
The /dev entries are:
% ls -l /dev/da0*f
brw-r----- 1 root operator 4, 5 Dec 24 20:06 /dev/da0f
brw-r----- 1 root operator 4, 0x00030005 Jul 1 1999 /dev/da0s2f
brw-r----- 1 root operator 4, 0x00040005 Jul 1 1999 /dev/da0s3f
Looking through the fstat.c source, in the ufs_filestat procedure, the
file system id is computed as:
int
ufs_filestat(vp, fsp)
struct vnode *vp;
struct filestat *fsp;
{
struct inode inode;
if (!KVM_READ(VTOI(vp), &inode, sizeof (inode))) {
dprintf(stderr, "can't read inode at %p for pid %d\n",
(void *)VTOI(vp), Pid);
return 0;
}
fsp->fsid = inode.i_dev & 0xffff;
That is, the 0xffff mask erases the high-order bits of the major/minor
number packing and makes da0f, da0s2f, and da0s3f appear to be the
same partition. Is this right?
Now, I don't know enough about Freebsd's treatment of minor numbers.
Is this a simple bug, fixable by removing the 0xffff mask? I tried
that, and it seems to work. Or, is the issue more complicated?
Or, should I just avoid creating Freebsd partitions on two slices of
the same disk?
--Mark Krentel
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-stable" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200001150709.CAA11205>