Re: LVM and XFS cannot set blocksize on block device

[Shailendra Tripathi <stripathi@agami.com>]

>>Thanks for the reply. The "-s size=4096" helped I was able to create
>>the file system, then mount it and use it.  I did however get a
>>warning still about "cannot set blocksize on block device".

> 
> I don't know much about the LVM code, my guess is that
> ioctl(... ,BLKBSZSET, ...) is failing, strace would confirm this.


libxfs_device_open () seems to be working with the pre-conceived notion 
of assuming block devices of only 512 bytes in size.

if (!readonly && setblksize && (statb.st_mode & S_IFMT) == S_IFBLK)
    platform_set_blocksize(fd, path, statb.st_rdev, 512);

This eventually calls to set the blk sz to 512. Since, your volume does 
not support less than 4k, it returns EINVAL. I think, libxfs_init should 
be modified to take pass on the -s size option to this call so that it 
does not happen.
      However, I don't see any problem despite this failure. Everything 
else should work fine.




>>Everything seems to be working but I am a bit worried about the
>>warning message.  Following is the message.  Any ideas if it is safe
>>to ignore this or any way to get rid of it?
> 
> 
> What does:
> 
>   blockdev --getbsz /dev/vg_u00/lv_u00
> 
> say?
> 
> 
> If mkfs.xfs is trying to set a blocksize that already matches the
> underlying device, it woudn't be hard to silence the warning by doing
> a check before unconditionally setting it, though I don't know that
> it's worth it.
> 
>