On my journey towards adding erofs support for initrd, Al Viro suggested to move the filesystem detection code into the respective filesystem modules. This patch series implements this, while also adding erofs support. To achieve this, I added a macro initrd_fs_detect() that allows filesystem modules to add a filesystem detection hooks. I then moved all existing filesystem detection code to this new API. While I was there I also tried to clean up some of the code. I've tested these changes with the following kinds of initrd images: - ext2 - Minix v1 - cramfs (padded/unpadded) - romfs - squashfs - erofs initrds are still relevant, because they have some advantages over initramfs. They don't require unpacking all files before starting the init process and allows them to stay compressed in memory. They also allow using advanced file system features, such as extended attributes. In the NixOS community, we are heavy users of erofs, due to its sweet spot of compression, speed and features. That being said, I'm totally in favor of cutting down the supported filesystems for initrd and further simplify the code. I would be surprised, if anyone is using ext2 or Minix v1 filesystems (64 MiB filesystem size limit!) or cramfs (16 MiB file size limit!) as an initrd these days! Squashfs and erofs seem genuinely useful, though. Signed-off-by: Julian Stecklina <julian.stecklina@xxxxxxxxxxxxxxxxxxxxx> --- Changes in v2: - Remove more legacy code - Introduce initrd_fs_detect - Move all other initrd filesystems to the new API - Link to v1: https://lore.kernel.org/r/20250320-initrd-erofs-v1-1-35bbb293468a@xxxxxxxxxxxxxxxxxxxxx --- Julian Stecklina (9): initrd: remove ASCII spinner initrd: fix double fput for truncated ramdisks initrd: add a generic mechanism to add fs detectors fs: minix: register an initrd fs detector fs: cramfs: register an initrd fs detector fs: romfs: register an initrd fs detector fs: squashfs: register an initrd fs detector fs: ext2, ext4: register an initrd fs detector fs: erofs: register an initrd fs detector fs/cramfs/Makefile | 5 ++ fs/cramfs/initrd.c | 41 +++++++++++++ fs/erofs/Makefile | 5 ++ fs/erofs/initrd.c | 19 ++++++ fs/ext2/Makefile | 5 ++ fs/ext2/initrd.c | 27 +++++++++ fs/ext4/Makefile | 4 ++ fs/minix/Makefile | 5 ++ fs/minix/initrd.c | 23 +++++++ fs/romfs/Makefile | 4 ++ fs/romfs/initrd.c | 22 +++++++ fs/squashfs/Makefile | 5 ++ fs/squashfs/initrd.c | 23 +++++++ include/asm-generic/vmlinux.lds.h | 6 ++ include/linux/ext2_fs.h | 9 --- include/linux/initrd.h | 37 ++++++++++++ init/do_mounts_rd.c | 122 ++++++++------------------------------ 17 files changed, 257 insertions(+), 105 deletions(-) --- base-commit: 88d324e69ea9f3ae1c1905ea75d717c08bdb8e15 change-id: 20250320-initrd-erofs-76e925fdf68c Best regards, -- Julian Stecklina <julian.stecklina@xxxxxxxxxxxxxxxxxxxxx>
