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Date: Mon, 29 Jan 2018 07:50:54 -0800
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Subject: Re: [PATCH v2] xfs: preserve i_rdev when recycling a reclaimable
 inode
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To: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>, Eryu Guan <eguan@redhat.com>, Miklos Szeredi <miklos@szeredi.hu>, linux-xfs <linux-xfs@vger.kernel.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>

On Mon, Jan 29, 2018 at 01:07:36PM +0200, Amir Goldstein wrote:
> On Fri, Jan 26, 2018 at 11:44 PM, Darrick J. Wong
> <darrick.wong@oracle.com> wrote:
> > On Fri, Jan 26, 2018 at 09:44:29AM +0200, Amir Goldstein wrote:
> >> Commit 66f364649d870 ("xfs: remove if_rdev") moved storing of rdev
> >> value for special inodes to VFS inodes, but forgot to preserve the
> >> value of i_rdev when recycling a reclaimable xfs_inode.
> >>
> >> This was detected by xfstest overlay/017 with inodex=on mount option
> >> and xfs base fs. The test does a lookup of overlay chardev and blockdev
> >> right after drop caches.
> >>
> >> Overlayfs inodes hold a reference on underlying xfs inodes when mount
> >> option index=on is configured. If drop caches reclaim xfs inodes, before
> >> it relclaims overlayfs inodes, that can sometimes leave a reclaimable xfs
> >> inode and that test hits that case quite often.
> >>
> >> When that happens, the xfs inode cache remains broken (zere i_rdev)
> >> until the next cycle mount or drop caches.
> >>
> >> Fixes: 66f364649d870 ("xfs: remove if_rdev")
> >> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> >
> > Looks ok,
> > Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> >
> 
> I recon that now we should now also strap:
> Cc: <stable@vger.kernel.org> #v4.15
> 
> Can I assume, you'll add it on apply?

I'll do a proper backport of this and a couple other critical cow
fixes after I get the 4.16 stuff merged.

--D

> Thanks,
> Amir.