linux-kernel - Re: Unionmount and overlayfs testsuite

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Date:	Fri, 30 May 2014 09:49:33 +0100
From:	David Howells <dhowells@...hat.com>
To:	"J. R. Okajima" <hooanon05g@...il.com>
Cc:	dhowells@...hat.com, Miklos Szeredi <miklos@...redi.hu>,
	viro@...IV.linux.org.uk, torvalds@...ux-foundation.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, akpm@...ux-foundation.org, apw@...onical.com,
	nbd@...nwrt.org, neilb@...e.de, jordipujolp@...il.com,
	ezk@....cs.sunysb.edu, sedat.dilek@...il.com, mszeredi@...e.cz
Subject: Re: Unionmount and overlayfs testsuite

J. R. Okajima <hooanon05g@...il.com> wrote:

> I've found some interesting cases.
> 
> - impermissible.test,
> 	open_file_as_bin -t -w $file -E EACCES
>   When $termslash is "/", a '/' is appended to the expanded $file, such
>   as "/path/fileA/". If fileA is a regular file, that path is obviously
>   wrong. Does UnionMount expect EACCES in this case too?
>   Should it be ENOTDIR?
>   It might be better to change
> 	errcode=EACCES
> 	test ! "$termslash" = "" && errcode=ENOTDIR
> 	open_file_as_bin -t -w $file -E $errcode

I'd never got to the end of the impermissible test because the utimes test
fails on both unionmount and overlayfs.  I'll have to address the termslash
alterations at some point.

> - readlink.test,
> 	fs_op readlink $file -R $testdir/direct_dir_sym100 ${termslash:+-E EINVAL}
>   It expects "$testdir/direct_dir_sym100". Does it mean UnionMount
>   converts the target path?
>   For example,
>   - /u = /rw + /ro
>   - /rw/symlinkA doesn't exist
>   - /ro/symlinkA points to /ro/fileA

No.  Unionmount unions are constructed by mounting the lower layers all on the
same mountpoint and then mounting the union over them, also on the same
mountpoint.  So their paths are coincident.

>   Does readlink(2) return "/u/fileA" instead of /ro/fileA?"

No.

The test suite sets the lower symlink to point to the union path for its target.

[root@...romeda union-testsuite]# readlink /lower/a/indirect_dir_sym100 
/mnt/a/direct_dir_sym100

> And all tests should be done by a superuser?

Yes.  It also will test things like mknod at some point and runs things as
other users to test permissions.

David
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