linux-ext4 - Re: e2fsck: set dir_nlink feature if large dir exists

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Message-ID: <20170830022000.b7mgzksytvcwirx5@thunk.org>
Date:   Tue, 29 Aug 2017 22:20:00 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: e2fsck: set dir_nlink feature if large dir exists

On Fri, Aug 18, 2017 at 12:19:42PM -0600, Andreas Dilger wrote:
> If there is a directory with more than EXT2_LINK_MAX (65000)
> subdirectories, but the DIR_NLINK feature is not set in the
> superblock, the feature should be set before continuing on
> to change the on-disk directory link count to 1.
> 
> While most filesystems should have DIR_NLINK set (it was set
> by default for all ext4 filesystems, and the kernel before
> 4.12 automatically set it if the directory link count grew
> too large), it is possible that this flag is lost due to disk
> corruption or for an upgraded filesystem.  We no longer want
> the kernel to automatically enable this feature.
> 
> Addresses: https://bugzilla.kernel.org/show_bug.cgi?id=196405
> Signed-off-by: Andreas Dilger <adilger@...ger.ca>

The f_large_dir test is now failing after I apply this patch:

debugfs 1.43.6 (29-Aug-2017)
./test_one: 38: /usr/projects/e2fsprogs/e2fsprogs/tests/f_large_dir/script: arithmetic expression: division by zero: "i / ELAPSED"
f_large_dir: optimize 3 level htree directories: failed

						- Ted