Re: [PATCH v2] xfs: preserve i_rdev when recycling a reclaimable inode

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Feb 01, 2018 at 02:27:23AM +0200, Amir Goldstein wrote:
> On Mon, Jan 29, 2018 at 5:50 PM, Darrick J. Wong
> <darrick.wong@oracle.com> wrote:
> > 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.
> >
> 
> I am not sure what "proper backport" means in the context of
> this patch.
> This is a v4.15-rc1 regression fix that is based on v4.15-rc8.
> It applied cleanly on v4.15.

I meant the other things that went into 4.16, like the reflink quota
fixes, the directio corruption problems, etc.  Make a branch, add the
necessary fixes, run xfstests to make sure it all still works, etc.

--D

> CC'ing stable for attention.
> 
> This patch is now in master, but due to its timing it did not
> get the CC: stable tag.
> 
> Thanks,
> Amir.
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