linux-ext4 - [Bug 220342] New: After file delete, extent index structure remains unchanged

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Message-ID: <bug-220342-13602@https.bugzilla.kernel.org/>
Date: Tue, 15 Jul 2025 13:29:25 +0000
From: bugzilla-daemon@...nel.org
To: linux-ext4@...r.kernel.org
Subject: [Bug 220342] New: After file delete, extent index structure remains
 unchanged

https://bugzilla.kernel.org/show_bug.cgi?id=220342

            Bug ID: 220342
           Summary: After file delete, extent index structure remains
                    unchanged
           Product: File System
           Version: 2.5
    Kernel Version: 6.16-rc6
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: ext4
          Assignee: fs_ext4@...nel-bugs.osdl.org
          Reporter: bretznic@...il.com
        Regression: No

Created attachment 308380
  --> https://bugzilla.kernel.org/attachment.cgi?id=308380&action=edit
ext

When a file without extents is deleted, eh_entries and eh_depth are cleared, as
well as ee_start_hi and ee_start_lo.

When a file with extents is deleted, eh_entries and eh_depth are also cleared,
but ei_leaf_hi and ei_leaf_lo are not cleared in the top inode.

The attached screenshots of hexdumps show the issue before vs. after deletion,
for non-extent and extent files.

With ei_leaf_hi and ei_leaf_lo still present, it's easy to reach the data
blocks.

Having said this, extent files have (regular) extent structures lower in the
tree, and those are not cleared. (Unlike the regular extent structures of
non-extent files)

I don't know if it's worth clearing those structures as well. I guess for most
instances it's not, and for security conscious users it would probably be a
nice to have. But then, where to stop? I don't know...

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