Date: Thu, 10 May 2001 03:20:05 -0700 (PDT) From: Jan Conrad <conrad@th.physik.uni-bonn.de> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/27232: On NFSv3 mounted filesystems, stat returns st_blksize=512 Message-ID: <200105101020.f4AAK5065603@freefall.freebsd.org>
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The following reply was made to PR kern/27232; it has been noted by GNATS.
From: Jan Conrad <conrad@th.physik.uni-bonn.de>
To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Cc: <freebsd-gnats-submit@FreeBSD.ORG>
Subject: Re: kern/27232: On NFSv3 mounted filesystems, stat returns st_blksize=512
Date: Thu, 10 May 2001 12:18:18 +0200 (CEST)
On Wed, 9 May 2001, Garrett Wollman wrote:
> <<On Wed, 9 May 2001 10:11:55 -0700 (PDT), conrad@th.physik.uni-bonn.de said:
>
> > On NFSv3 mounts, stat returns st_blksize=512 for every regular file.
> > This in turn is used by libc routines as a default buffer size, as it
> > should be the 'optimal' io blocksize.
>
> No. It should be the block size used by the underlying filesystem's
> block allocator, and in which the file's `st_blocks' size-on-disk is
> reported. While SUS describes it as a ``preferred'' block size, and
> the FreeBSD manual pages describe it as ``optimal ... for I/O'', the
> most important meaning of this field is as a multiplier of st_blocks
> to determine the file's size.
Hmm - I am sorry, but I can't believe your answer.
If I stat the following file on /var/tmp (newfs'd with -b 8192 -f 1024)
(all with FreeBSD 4.3R)
-rw-r--r-- 1 root wheel 33398 Mar 13 17:40 /var/tmp/dev.out
# my little stat checker (appended to the message) gives me
./stat
/var/tmp/dev.out:
st_mode = 100644
st_blksize = 8192
st_size = 33398
st_blocks = 66
As you can see st_blocks measures the size of the file in 512byte blocks
independent of st_blksize!
And the source of this is ufs_getattr in sys/ufs/ufs/ufs_vnops.c
(this is present in HEAD!)
vap->va_flags = ip->i_flags;
vap->va_gen = ip->i_gen;
vap->va_blocksize = vp->v_mount->mnt_stat.f_iosize;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
vap->va_bytes = dbtob((u_quad_t)ip->i_blocks);
vap->va_type = IFTOVT(ip->i_mode);
So either ufs or nfs is wrong (or both!)
-Jan
The output is from the following little program
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define FILE1 "/milles/home/conrad/src/stat/stat.c"
#define FILE2 "/.amd_mnt/avz109/users/Math_Dictionary/readme.htm"
#define FILE3 "/var/tmp/dev.out"
main()
{
struct stat sb;
char *file = FILE3;
if (stat(file, &sb) < 0) {
printf ("fail\n");
} else {
printf ("%s:\n", file);
printf ("st_mode = %o\n", sb.st_mode);
printf ("st_blksize = %u\n", sb.st_blksize);
printf ("st_size = %u\n", sb.st_size);
printf ("st_blocks = %U\n", sb.st_blocks);
};
}
>
> -GAWollman
>
> --
> Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same
> wollman@lcs.mit.edu | O Siem / The fires of freedom
> Opinions not those of| Dance in the burning flame
> MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick
>
--
Physikalisches Institut der Universitaet Bonn
Nussallee 12
D-53115 Bonn
GERMANY
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