linux-kernel - Re: linux-next: manual merge of the userns tree

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Message-ID: <87k3h8escj.fsf@xmission.com>
Date:	Sat, 19 Oct 2013 16:47:08 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Mark Brown <broonie@...nel.org>
Cc:	"Eric W. Biederman" <ebiederman@...tter.com>,
	Miklos Szeredi <mszeredi@...e.cz>,
	Miklos Szeredi <miklos@...redi.hu>,
	Thierry Reding <thierry.reding@...il.com>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: linux-next: manual merge of the userns tree

Mark Brown <broonie@...nel.org> writes:

> Today's linux-next merge of the userns tree got a conflict in
> fs/fuse/dir.c between 3c70b8eed (fuse: don't check_submounts_and_drop()
> in RCU walk) in the fuse tree and 40216baa0 (vfs: Lazily remove mounts
> on unlinked files and directories. v2) in the userns tree.
>
> I fixed it up as below and can carry as required:

The fix looks right.

However I think this conflict highlights a larger issue, as there are
several other filesystems that call check_submounts_and_drop from the
devalidate and possibly from rcu_walk today.

Miklos what problem did you run into?

Sigh.  It looks like it probably makes sense to merge
shrink_submounts_and_drop with d_invalidate, so filesystems don't even
need to think about this issue.

Eric

> diff --cc fs/fuse/dir.c
> index 0747f6e,b1cd7b7..0000000
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@@ -263,9 -259,7 +263,10 @@@ out
>   
>   invalid:
>   	ret = 0;
>  -	shrink_submounts_and_drop(entry);
>  +
> - 	if (!(flags & LOOKUP_RCU) && check_submounts_and_drop(entry) != 0)
> - 		ret = 1;
> ++	if (!(flags & LOOKUP_RCU))
> ++		shrink_submounts_and_drop(entry);
> ++
>   	goto out;
>   }
>   
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