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From: Sun YangKai <sunk67188@gmail.com>
To: linux-btrfs <linux-btrfs@vger.kernel.org>
Cc: sunk67188@gmail.com
Subject: Newbie questions about DIR_ITEM and DIR_INDEX design
Date: Wed, 20 Aug 2025 21:59:58 +0800	[thread overview]
Message-ID: <12726025.O9o76ZdvQC@saltykitkat> (raw)

Hello btrfs developers

I am a beginner studying the implementation of btrfs. While examining the 
structures of DIR_ITEM and DIR_INDEX, I noticed that both store similar 
content but differ in their offset values. This led me to two questions:

1. The offset field in DIR_ITEM is computed as a CRC32 hash of the filename. In 
practice, is there a risk of hash collisions? If so, how does the current 
implementation handle such collisions?

2. The offset field in DIR_INDEX appears to be an auto-incrementing number, 
possibly indicating the creation order of entries within a directory. Why is 
this necessary, given that DIR_ITEM already exists?

I would greatly appreciate any insights or references to relevant 
documentation or code snippets to help me understand these design choices.

Thank you for your time and guidance.

Best regards,
Sun YangKai



             reply	other threads:[~2025-08-20 14:00 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-08-20 13:59 Sun YangKai [this message]
2025-08-20 17:06 ` Newbie questions about DIR_ITEM and DIR_INDEX design Mark Harmstone
2025-08-21  8:26   ` Sun YangKai
2025-08-21  9:20     ` Mark Harmstone
2025-08-21 10:06       ` Sun YangKai

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