linux-ext4 - Re: One more corrupted fs crash in ext4_put

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Date:	Thu, 9 Oct 2014 23:15:41 +0300
From:	Sami Liedes <sami.liedes@....fi>
To:	linux-ext4@...r.kernel.org
Subject: Re: One more corrupted fs crash in ext4_put_super

On Tue, Oct 07, 2014 at 11:56:43PM +0300, Sami Liedes wrote:
> Here's one more filesystem that causes a crash in ext4_put_super on
> 3.17 both with and without the two patches from this thread applied.

Ok, I bisected a bit. FWIW.

No crash on 3.16.4 + these two patches:

1c8944cbe1b ext4: add ext4_iget_normal() which is to be used for dir tree lookups
b65ad45743c ext4: don't orphan or truncate the boot loader inode

Crash on 3.17 + the above two patches.

The first commit that crashes on this test with the above patches:

# first bad commit: [908790fa3b779d37365e6b28e3aa0f6e833020c3] dcache: d_splice_alias mustn't create directory aliases

commit 908790fa3b779d37365e6b28e3aa0f6e833020c3
Author: J. Bruce Fields <bfields@...hat.com>
Date:   Mon Feb 17 17:58:42 2014 -0500

    dcache: d_splice_alias mustn't create directory aliases

    Currently if d_splice_alias finds a directory with an alias that is not
    IS_ROOT or not DCACHE_DISCONNECTED, it creates a duplicate directory.

    Duplicate directory dentries are unacceptable; it is better just to
    error out.

    (In the case of a local filesystem the most likely case is filesystem
    corruption: for example, perhaps two directories point to the same child
    directory, and the other parent has already been found and cached.)

    Note that distributed filesystems may encounter this case in normal
    operation if a remote host moves a directory to a location different
    from the one we last cached in the dcache.  For that reason, such
    filesystems should instead use d_materialise_unique, which tries to move
    the old directory alias to the right place instead of erroring out.

    Signed-off-by: J. Bruce Fields <bfields@...hat.com>
    Signed-off-by: Al Viro <viro@...iv.linux.org.uk>

-- 

	Sami

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