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[bug #61606] Grub should support ext2/ext4 file systes with the large_di


From: Theodore Tso
Subject: [bug #61606] Grub should support ext2/ext4 file systes with the large_dir feature
Date: Thu, 2 Dec 2021 20:11:14 -0500 (EST)
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

URL:
  <https://savannah.gnu.org/bugs/?61606>

                 Summary: Grub should support ext2/ext4 file systes with the
large_dir feature
                 Project: GNU GRUB
            Submitted by: tytso
            Submitted on: Fri 03 Dec 2021 01:11:12 AM UTC
                Category: Filesystem
                Severity: Major
                Priority: 5 - Normal
              Item Group: Feature Request
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: tytso@mit.edu
             Open/Closed: Open
                 Release: 
                 Release: Git master
         Discussion Lock: Any
         Reproducibility: Every Time
         Planned Release: None

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Details:

Grub uses the fs/ext2.c code to support ext2/ext3/ext4 file systems.

Recently, ext4 added the a large_dir feature, which adds support for a 3 level
htree directory support.   Grub supports existing file systems with htree
directories by ignoring their existence, and since the index nodes for the
hash tree look like deleted directory entries (by design), grub can simply do
a brute force O(n) linear search of directories.   The same is true for 3
level deep htrees indicated by large_dir feature flag.   Hence, all that is
needed for grub to support large_dir file systems is to add the following
definition to grub-core/fs/ext2.c:

#define EXT4_FEATURE_INCOMPAT_LARGEDIR          0x4000 /* >2GB or 3-lvl htree */

And then add that bit into the macro EXT2_DRIVER_SUPPORT_INCOMPAT.



    _______________________________________________________

File Attachments:


-------------------------------------------------------
Date: Fri 03 Dec 2021 01:11:12 AM UTC  Name: diff  Size: 1KiB   By: tytso

<http://savannah.gnu.org/bugs/download.php?file_id=52412>

    _______________________________________________________

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