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From: Amir Goldstein <>
To: Chris Murphy <>
Cc: Miklos Szeredi <>,
	Btrfs BTRFS <>,
	overlayfs <>
Subject: Re: btrfs+overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off.
Date: Sat, 10 Apr 2021 20:55:18 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Sat, Apr 10, 2021 at 8:36 PM Chris Murphy <> wrote:
> I can reproduce the bolt testcase problem in a podman container, with
> overlay driver, using ext4, xfs, and btrfs. So I think I can drop
> linux-btrfs@ from this thread.
> Also I can reproduce the title of this thread simply by 'podman system
> reset' and see the kernel messages before doing the actual reset. I
> have a strace here of what it's doing:

I'm confused. The error in the title of the page is from overlayfs mount().
I see no mount in the strace.
I feel that I am missing some info.
Can you provide the overlayfs mount arguments
and more information about the underlying layers?

> It may be something intentional. The failing testcase,
> :../tests/test-common.c:1413:test_io_dir_is_empty also has more
> instances of this line, but I don't know they are related. So I'll
> keep looking into that.
> On Sat, Apr 10, 2021 at 2:04 AM Amir Goldstein <> wrote:
> > As the first step, can you try the suggested fix to ovl_dentry_version_inc()
> > and/or adding the missing pr_debug() and including those prints in
> > your report?
> I'll work with bolt upstream and try to further narrow down when it is
> and isn't happening.
> > > I can reproduce this with 5.12.0-0.rc6.184.fc35.x86_64+debug and at
> > > approximately the same time I see one, sometimes more, kernel
> > > messages:
> > >
> > > [ 6295.379283] overlayfs: upper fs does not support xattr, falling
> > > back to index=off and metacopy=off.
> > >
> >
> > Can you say why there is no xattr support?
> I'm not sure. It could be podman specific or fuse-overlayfs related.

Not sure how fuse-overlayfs is related.
This is a message from overlayfs kernel driver.

> Maybe something is using /tmp in one case and not another for some
> reason?
> > Is the overlayfs mount executed without privileges to create trusted.* xattrs?
> > The answer to that may be the key to understanding the bug.
> Yep. I think tmpfs supports xattr but not user xattr? And this example
> is rootless podman, so it's all unprivileged.

OK, so unprivileged overlayfs mount support was added in v5.11
and it requires opt-in with mount option "userxattr", which could
explain the problem if tmpfs is used as upper layer.

Do you know if that is the case?
I sounds to me like it may not be a kernel regression per-se,
but a regression in the container runtime that started to use
a new kernel feature?
Need more context to understand.

Perhaps the solution will be to add user xattr support to tmpfs..


  reply	other threads:[~2021-04-10 17:55 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-09 22:03 btrfs+overlayfs: upper fs does not support xattr, falling back to index=off and metacopy=off Chris Murphy
2021-04-10  8:03 ` Amir Goldstein
2021-04-10 17:36   ` Chris Murphy
2021-04-10 17:55     ` Amir Goldstein [this message]
2021-04-10 19:36       ` Chris Murphy
2021-04-10 19:42         ` Chris Murphy
2021-04-10 19:43           ` Chris Murphy
2021-04-10 19:44             ` Chris Murphy
2021-04-10 20:03               ` Chris Murphy
2021-04-11  5:12                 ` Amir Goldstein
2021-04-11  6:05                   ` Chris Murphy
2021-04-11  7:28                     ` Amir Goldstein
2021-04-13 21:50                       ` Chris Murphy
2021-04-12  8:41       ` Miklos Szeredi

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