Date: Fri, 18 Jan 2002 21:41:29 +0600 (NOVT) From: Alexey Dokuchaev <danfe@inet.ssc.nsu.ru> To: arch@freebsd.org Subject: Re: request for review Message-ID: <Pine.LNX.4.10.10201182141050.13875-100000@inet.ssc.nsu.ru>
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Hello!
The following program was compiled and run on different systems in order
to examine their behaviour with respect to st_blksize returned for tty:
#include <sys/types.h>
#include <sys/stat.h>
void
f(int fd)
{
struct stat s;
fstat(fd, &s);
printf("fd %d: st_blksize: %d, st_mode: (0%08o)\n",
fd, s.st_blksize, (unsigned) s.st_mode);
}
main()
{
f(0);
f(1);
return 0;
}
The results obtained are:
OpenBSD 2.9 (i386):
fd 0: st_blksize: 65536, st_mode: (000020620)
fd 1: st_blksize: 65536, st_mode: (000020620)
---
SunOS 5.6 (sun4u sparc SUNW,Ultra-Enterprise):
fd 0: st_blksize: 8192, st_mode: (000020620)
fd 1: st_blksize: 8192, st_mode: (000020620)
---
Linux 2.2.19 and 2.4.16 (i686):
fd 0: st_blksize: 1024, st_mode: (000020620)
fd 1: st_blksize: 1024, st_mode: (000020620)
---
FreeBSD 4.4-STABLE (December 6, 2001, August ?, 2001):
fd 0: st_blksize: 0, st_mode: (000020620)
fd 1: st_blksize: 0, st_mode: (000020620)
Note that I stated the values for two -STABLE systems of mine, the reason
for doing so arised from the same tests I conducted on both systems
*after* I've applied the patch suggested by Max:
FreeBSD 4.4-STABLE (December 6, 2001), with patched vfs_vnops.c:
fd 0: st_blksize: 16384, st_mode: (000020620)
fd 1: st_blksize: 16384, st_mode: (000020620)
---
FreeBSD 4.4-STABLE (August ?, 2001), with patched vfs_vnops.c
fd 0: st_blksize: 8192, st_mode: (000020620)
fd 1: st_blksize: 8192, st_mode: (000020620)
Note the different values returned for st_blksize in both cases.
> Date: Tue, 15 Jan 2002 06:34:44 -0800
> From: Cy Schubert - ITSD Open Systems Group <Cy.Schubert@uumail.gov.bc.ca>
> To: Poul-Henning Kamp <phk@critter.freebsd.dk>
> Cc: Max Khon <fjoe@iclub.nsu.ru>, arch@freebsd.org
> Subject: Re: request for review
>
> In addition to making FreeBSD consistent with OpenBSD and Linux, as
> stated by the originator of this thread, the patch also makes FreeBSD
> consistent with Solaris and Tru64-UNIX. I'm for it.
That's exactly what bugs me! According to my tests, things are not quite
consistent even within *BSD. Right now I do not have time to dig into the
source code to get an explanation of why OpenBSD returned 64K, -CURRENT
(according to Max) returned 512 bytes (!), and two of my -STABLE systems
yielded different numbers as well. Maybe someone has the explanation
off-hand, in this case, I'd appreciate the one sharing it with us :-)
> > >? current-diffs
> > >Index: vfs_vnops.c
> > >===================================================================
> > >RCS file: /home/ncvs/src/sys/kern/vfs_vnops.c,v
> > >retrieving revision 1.125
> > >diff -u -p -r1.125 vfs_vnops.c
> > >--- vfs_vnops.c 18 Dec 2001 20:48:54 -0000 1.125
> > >+++ vfs_vnops.c 14 Jan 2002 18:04:45 -0000
> > >@@ -579,6 +579,8 @@ vn_stat(vp, sb, td)
> > > sb->st_blksize = vp->v_rdev->si_bsize_phys;
> > > if (sb->st_blksize < BLKDEV_IOSIZE)
> > > sb->st_blksize = BLKDEV_IOSIZE;
> > >+ } else if (vap->va_type == VCHR) {
> > >+ sb->st_blksize = vap->va_blocksize;
> > > } else {
> > > sb->st_blksize = 0;
> > > }
And the last thing, I've been looking at the patch, and thought, maybe it
would be more clear to patch vfs_vnops.c the following way instead:
--- /sys/kern/vfs_vnops.c.orig Fri Jan 18 21:16:33 2002
+++ /sys/kern/vfs_vnops.c Thu Jan 17 20:26:11 2002
@@ -530,7 +530,7 @@
* Default to zero to catch bogus uses of this field.
*/
- if (vap->va_type == VREG) {
+ if (vap->va_type == VREG || vap->va_type == VCHR) {
sb->st_blksize = vap->va_blocksize;
} else if (vn_isdisk(vp, NULL)) {
sb->st_blksize = vp->v_rdev->si_bsize_best;
What do you think?
Sincerely,
DAN Fe
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