linux-ext4 - Re: Fast symlinks stored slow

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Date:   Wed, 12 Jul 2017 14:36:23 -0700
From:   Tahsin Erdogan <tahsin@...gle.com>
To:     "Richard W.M. Jones" <rjones@...hat.com>,
        Andreas Dilger <adilger@...ger.ca>,
        "Theodore Ts'o" <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: Fast symlinks stored slow

>> To cut a long story short, we were using libext2fs to create
>> filesystems where short symlinks (< 60 bytes) were stored the same way
>> as long symlinks, ie. stored as an ordinary file instead of being
>> stored in the inode.
>
> As a further data point, e2fsck does not complain about these
> filesystems.

This sounds bad. We may have to revert back to i_blocks based logic.

As an example, lets say inode's EXT4_INODE_EXTENTS flag is clear,
i_size is 2 and i_data[0] contains 0x00004141. Without inspecting
xattrs and i_blocks, we can't determine whether a) the target is "AA"
or b) block 0x4141 contains two bytes that is the actual symlink
target.