linux-ext4 - Re: [PATCH] Add largedir feature

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Date:   Mon, 1 May 2017 22:44:42 -0400
From:   Theodore Ts'o <tytso@....edu>
To:     Andreas Dilger <adilger@...ger.ca>
Cc:     Eric Biggers <ebiggers3@...il.com>,
        Artem Blagodarenko <artem.blagodarenko@...gate.com>,
        linux-ext4 <linux-ext4@...r.kernel.org>,
        Alexey Lyashkov <alexey.lyashkov@...il.com>,
        Yang Sheng <yang.sheng@...el.com>,
        Artem Blagodarenko <artem.blagodarenko@...il.com>
Subject: Re: [PATCH] Add largedir feature

On Mon, May 01, 2017 at 05:39:41PM -0600, Andreas Dilger wrote:
> > FYI, this patch is causing a problem when creating many files in a directory
> > (without the largedir feature enabled).  I haven't looked into it but maybe it
> > will ring a bell for someone.
> 
> Hmm, is this also a problem without the patch, when creating large numbers
> of entries in a directory?

No, it works fine without the patch.  Turnkey reproduction for
kvm-xfstests which works fine without the largedir patch, but which
fails with the largedir patch:

   mke2fs -t ext4 -Fq /dev/vdc
   mount /vdc
   mkdir /vdc/a
   cd /vdc/a
   seq -f "abcdefghijklmnopqrstuvwxyz012345%.0f" 100000 | xargs touch
   umount /vdc
   e2fsck -fy /dev/vdc

The output of e2fsck:

e2fsck 1.43.5-WIP-ed1e950f (26-Apr-2017)
Pass 1: Checking inodes, blocks, and sizes
Inode 131073, i_size is 2080768, should be 2084864.  Fix? yes

Pass 2: Checking directory structure
Problem in HTREE directory inode 131073: root node fails checksum.
Clear HTree index? yes

Pass 3: Checking directory connectivity
Pass 3A: Optimizing directories
Pass 4: Checking reference counts
Pass 5: Checking group summary information

/dev/vdc: ***** FILE SYSTEM WAS MODIFIED *****
/dev/vdc: 30705/327680 files (0.0% non-contiguous), 42515/1310720 blocks

It looks the large_dir patch is responsible for a test regression ---
it is causing generic/339 to fail.

I'm going to drop the large dir patch for the 4.12 merge window.
Eric, thanks for noticing and pointing this out!

						- Ted