On Tue, Nov 26, 2013 at 06:31:19PM -0800, Phil White wrote:
> 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
> 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
> 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.
That doesn't mean it is correct, because the man page also says:
" In Linux alignment restrictions vary by filesystem and kernel
version and might be absent entirely."
So, I bet that your underlying filesystem (i.e. the host filesystem)
has a sector size of 4k, and that's why direct Io on 512 byte
alignment is failing. In that case, run "mkfs.xfs -s size=4k ..."
and mkfs should just work fine...