fs/erofs: Add support for the EROFS

The EROFS [1] is a lightweight read-only filesystem designed for performance
which has already been shipped in most Linux distributions as well as widely
used in several scenarios, such as Android system partitions, container
images and rootfs for embedded devices.

This patch brings in the EROFS uncompressed support. Now, it's possible to
boot directly through GRUB with an EROFS rootfs.

Support for the EROFS compressed files will be added later.

[1] https://erofs.docs.kernel.org

Signed-off-by: Yifan Zhao <zhaoyifan@sjtu.edu.cn>
Tested-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

INSTALL

@@ -77,15 +77,15 @@ Prerequisites for make-check:
 
 * If running a Linux kernel the following modules must be loaded:
   - fuse, loop
-  - btrfs, ext4, f2fs, fat, hfs, hfsplus, jfs, mac-roman, minix, nilfs2,
+  - btrfs, erofs, ext4, f2fs, fat, hfs, hfsplus, jfs, mac-roman, minix, nilfs2,
     reiserfs, udf, xfs
   - On newer kernels, the exfat kernel modules may be used instead of the
     exfat FUSE filesystem
 * The following are Debian named packages required mostly for the full
   suite of filesystem testing (but some are needed by other tests as well):
-  - btrfs-progs, dosfstools, e2fsprogs, exfat-utils, f2fs-tools, genromfs,
-    hfsprogs, jfsutils, nilfs-tools, ntfs-3g, reiserfsprogs, squashfs-tools,
-    reiserfsprogs, udftools, xfsprogs, zfs-fuse
+  - btrfs-progs, dosfstools, e2fsprogs, erofs-utils, exfat-utils, f2fs-tools,
+    genromfs, hfsprogs, jfsutils, nilfs-tools, ntfs-3g, reiserfsprogs,
+    squashfs-tools, reiserfsprogs, udftools, xfsprogs, zfs-fuse
   - exfat-fuse, if not using the exfat kernel module
   - gzip, lzop, xz-utils
   - attr, cpio, g++, gawk, parted, recode, tar, util-linux

Makefile.util.def

@@ -98,6 +98,7 @@ library = {
   common = grub-core/fs/cpio_be.c;
   common = grub-core/fs/odc.c;
   common = grub-core/fs/newc.c;
+  common = grub-core/fs/erofs.c;
   common = grub-core/fs/ext2.c;
   common = grub-core/fs/fat.c;
   common = grub-core/fs/exfat.c;

docs/grub.texi

@@ -353,6 +353,7 @@ blocklist notation. The currently supported filesystem types are @dfn{Amiga
 Fast FileSystem (AFFS)}, @dfn{AtheOS fs}, @dfn{BeFS},
 @dfn{BtrFS} (including raid0, raid1, raid10, gzip and lzo),
 @dfn{cpio} (little- and big-endian bin, odc and newc variants),
+@dfn{EROFS} (only uncompressed support for now),
 @dfn{Linux ext2/ext3/ext4}, @dfn{DOS FAT12/FAT16/FAT32},
 @dfn{exFAT}, @dfn{F2FS}, @dfn{HFS}, @dfn{HFS+},
 @dfn{ISO9660} (including Joliet, Rock-ridge and multi-chunk files),
@@ -6276,7 +6277,7 @@ assumed to be encoded in UTF-8.
 NTFS, JFS, UDF, HFS+, exFAT, long filenames in FAT, Joliet part of
 ISO9660 are treated as UTF-16 as per specification. AFS and BFS are read
 as UTF-8, again according to specification. BtrFS, cpio, tar, squash4, minix,
-minix2, minix3, ROMFS, ReiserFS, XFS, ext2, ext3, ext4, FAT (short names),
+minix2, minix3, ROMFS, ReiserFS, XFS, EROFS, ext2, ext3, ext4, FAT (short names),
 F2FS, RockRidge part of ISO9660, nilfs2, UFS1, UFS2 and ZFS are assumed
 to be UTF-8. This might be false on systems configured with legacy charset
 but as long as the charset used is superset of ASCII you should be able to

grub-core/Makefile.core.def

@@ -1442,6 +1442,11 @@ module = {
   common = fs/odc.c;
 };
 
+module = {
+  name = erofs;
+  common = fs/erofs.c;
+};
+
 module = {
   name = ext2;
   common = fs/ext2.c;