Re: WARNING: at fs/block_dev.c:5 when removing LV on removed device

[Mike Snitzer <snitzer@redhat.com>]

On Thu, Jun 18 2015 at  2:08pm -0400,
Andi Kleen <andi@firstfloor.org> wrote:

> > Hmm, so you have a filesystem active on it too?
> 
> I unmounted it before.
> 
> >  
> > > Also the VG removal did not work of course.
> > 
> > Once you resolve the filesystem piece, from vgremove man page:
> > 
> > "vgremove allows you to remove one or more volume groups.  If one or
> > more physical volumes in the volume group are lost, consider vgreduce
> > --removemissing to make the volume group metadata consistent again."
> 
> Well in any case there should not be WARN()s.

Yes well I don't even know what WARN_ON you're hitting.  You're running
a 4.0.4 fedora kernel.  Which WARN_ON() is triggering?  The
WARN_ON_ONCE() in bdev_write_inode()? -- likely since the only caller of
bdev_write_inode is __blkdev_put...

/**
 * write_inode_now      -       write an inode to disk
 * @inode: inode to write to disk
 * @sync: whether the write should be synchronous or not
 *
 * This function commits an inode to disk immediately if it is dirty. This is
 * primarily needed by knfsd.
 *
 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
 */

So I have no idea why bdev_write_inode() is using WARN_ON_ONCE.. makes
since that write_inode_now() will fail if the disk no longer exists.  SO
the WARN_ON_ONCE seems misplaced.

Git blame shows its all hch's fault:

564f00f6c (Christoph Hellwig  2015-01-14 10:42:33 +0100   57) WARN_ON_ONCE(write_inode_now(inode, true));

564f00f6c block_dev: only write bdev inode on close