[DragonFlyBSD - Bug #3451] ext2fs: read ext4 extent-mapped inodes (read-only)

[liweitianux]

Issue #3451 has been updated by liweitianux.


Hi, how should we handle this together with #3355?  By the way, there is an ext2fs PR on GitHub: "ext2: sync FreeBSD changes except large sectorsize disks support":https://github.com/DragonFlyBSD/DragonFlyBSD/pull/31.  I'd like we can handle all of them.

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Bug #3451: ext2fs: read ext4 extent-mapped inodes (read-only)
http://bugs.dragonflybsd.org/issues/3451#change-14862

* Author: sigttou
* Status: New
* Priority: Normal
* Category: Driver
* Target version: 6.6
* Start date: 2026-10-16
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@ext2fs@ advertises @EXT2F_INCOMPAT_EXTENTS@, but the extent lookup path is
stubbed out: @ext4_bmapext()@ and @ext4_ext_find_extent()@ both return @EINVAL at . @mkfs.ext4@ creates every
inode extent-mapped by default, so a read-only mount of a Linux ext4 filesystem succeeds (@statfs@
reads only the superblock) but every directory lookup and @readdir@ fails with @EINVAL at .

Port the read-only extent tree walk and the extent bmap from FreeBSD main
(d7d237ce731f), following the extent read path (d7511a40a749, b394cd1e28f1, 5679656e09fb).

The extent write path (allocation, truncation and removal) remains unimplemented.

The second patch is required for @metadata_csum@ filesystems (directory block checksums)

---Files--------------------------------
0001-ext2fs-read-ext4-extent-mapped-inodes.patch (14.1 KB)
0002-ext2fs-do-not-synthesize-a-generation-number-on-inod.patch (1.58 KB)


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