linux-kernel - Overlayfs rename bug

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Date:	Tue, 24 Jun 2014 17:46:14 +0100
From:	David Howells <dhowells@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	dhowells@...hat.com, Sedat Dilek <sedat.dilek@...il.com>,
	"J. R. Okajima" <hooanon05g@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robo Bot <apw@...onical.com>, Felix Fietkau <nbd@...nwrt.org>,
	Neil Brown <neilb@...e.de>,
	Jordi Pujol <jordipujolp@...il.com>, ezk@....cs.sunysb.edu,
	"mszeredi@...e.cz" <mszeredi@...e.cz>
Subject: Overlayfs rename bug

Miklos Szeredi <miklos@...redi.hu> wrote:

> > Tentative Tested-by from me unless I can break it.
> 
> Thanks for testing.

Tested-by retracted temporarily.  There's a bug in rename handling.  If you
clone:

	http://git.infradead.org/users/dhowells/unionmount-testsuite.git

and check out the switch-to-python branch and do:

	./run --no rename-mass

then this works with no unioning used, but if you do:

	./run --ov rename-mass

to run it on overlayfs, then the following occurs:

	[root@...romeda union-testsuite]# ./run --ov rename-mass
	***
	*** ./run --ov --ts=0 rename-mass
	***
	TEST rename-mass.py:15: Mass rename sequential files into each other's vacated name slots
	 ./run --rename /mnt/a/foo103 /mnt/a/foo104
	 ./run --rename /mnt/a/foo102 /mnt/a/foo103
	 ./run --rename /mnt/a/foo101 /mnt/a/foo102
	 ./run --rename /mnt/a/foo100 /mnt/a/foo101
	 ./run --rename /mnt/a/foo104 /mnt/a/foo105
	/mnt/a/foo104: File unexpectedly found

strace shows:

	rename("/mnt/a/foo104", "/mnt/a/foo105") = 0
	lstat("/mnt/a/foo104", {st_mode=S_IFREG|0644, st_size=12, ...}) = 0

which shouldn't happen.

The kernel is 17eb601eb5dbc8a2e200872380c03400813d4f1a from overlayfs.v22.

David
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