git: ext2fs: refuse read-write mounts of extent filesystems

[Aaron LI]

commit 91bbce815a3db4bc65ba77b76b4e8ad92d57c23a
Author: David Bidner <david at crap.solutions>
Date:   Thu Oct 22 14:04:01 2026 +0200

    ext2fs: refuse read-write mounts of extent filesystems
    
    The extent reader cannot write: with EXT2F_INCOMPAT_EXTENTS set a
    read-write mount lets inode and directory updates through and only then
    fails the data blocks with EINVAL, leaving the filesystem inconsistent
    (e2fsck reports a file with a size but no blocks).
    
    Refuse the read-write mount with the same warning style as the other
    unsupported-feature checks.  Read-only mounts are unaffected and can
    still be reloaded; upgrading such a mount to read-write is refused.
    
    ext2_reload() asked ext2_check_sb_compat() with a hard-coded "not
    read-only", so a read-only reload of an extent filesystem failed with
    EIO once this check existed.  Pass the mount's read-only state.
    
    The check keys on the filesystem feature bit, so an ext3 filesystem
    converted with tune2fs -O extents is refused for read-write mounts too,
    although it mounted read-write before this change.
    
    An inode with the extents flag on a filesystem without the feature bit
    is not covered by the check: it takes the extent path, and mounted
    read-write it can reach the unimplemented write path, as before.
    Mounting untrusted images read-write remains unsupported.
    
    Bug: https://bugs.dragonflybsd.org/issues/3451

Summary of changes:
 sys/vfs/ext2fs/ext2_vfsops.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/91bbce815a3db4bc65ba77b76b4e8ad92d57c23a


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