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

From: Mike Snitzer
Date: Thu Jun 18 2015 - 14:16:31 EST

On Thu, Jun 18 2015 at 2:08pm -0400,
Andi Kleen <andi@xxxxxxxxxxxxxx> 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
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