Gents:
I was making an image for a VM using everyone's favorite fs with a line
that looked something like this:
-------------
dd if=/dev/zero of=~/image bs=1024 count=1048576 && ./mkfs/mkfs.xfs && mount -o loop ~/image /mnt/loop
-------------
mkfs.xfs gave me this output:
-------------
meta-data=/root/image isize=256 agcount=4, agsize=65536 blks
= sectsz=512 attr=2, projid32bit=0
data = bsize=4096 blocks=262144, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
existing superblock read failed: Invalid argument
mkfs.xfs: pwrite64 failed: Invalid argument
mkfs.xfs: read failed: Invalid argument
-------------
And, of course, it failed to mount.
Knowing that this was using a possibly old version of xfsprogs (3.1.10, it
turned out), I grabbed the git tree and tried that. The same problem occurred.
The "existing superblock read" problem was from mkfs/xfs_mkfs.c @ 806 in
zero_old_xfs_structures():
-------------
if (pread(xi->dfd, buf, new_sb->sb_sectsize, 0) != new_sb->sb_sectsize) {
fprintf(stderr, _("existing superblock read failed: %s\n"),
strerror(errno));
free(buf);
return;
}
-------------
The pwrite64 problem was from libxfs/rdwr.c @ 806 in __write_buf():
-------------
sts = pwrite64(fd, buf, len, offset);
if (sts < 0) {
int error = errno;
fprintf(stderr, _("%s: pwrite64 failed: %s\n"),
progname, strerror(error));
if (flags & LIBXFS_B_EXIT)
exit(1);
return error;
} else if (sts != len) {
fprintf(stderr, _("%s: error - pwrite64 only %d of %d bytes\n"),
progname, sts, len);
if (flags & LIBXFS_B_EXIT)
exit(1);
return EIO;
}
-------------
While it occurred to me that the problem might just be line 806 of some files
in xfsprogs, I threw it under a debugger and took a closer look. The file
descriptor value in xi->dfd pointed at ~/image. errno was set to 22. I
thought that might indicate a problem with lseek(), so I rewrote the pwrite64()
and pread() as lseek()s and read()/write()
As you may have guessed, this did me no good at all.
It's trying to read/write 512 bytes at the beginning of the file which seems
reasonably innocuous. I double checked the man page which says that under
2.6, O_DIRECT writes can be aligned to 512 bytes without a problem. sbp comes
out with 4096 in blocksize and 512 in sectsize when zero_old_xfs_structures()
is called and the first error comes up, so I'm at a loss for what's going wrong.
-Phil
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