Add support for erofs filesystems

Since Linux 5.4 a new read-only filesystem is available, erofs.
Compared to squashfs it offers much better read performance with and
without compression enabled.
It suppports two optional compressors, lz4 and lz4hc.

>From the mkfs.erofs man page:
EROFS is a new enhanced lightweight linux read-only filesystem with
modern designs (eg. no buffer head, reduced metadata, inline
xattrs/data, etc.) for scenarios which need high-performance read-only
requirements, e.g. Android OS for smartphones and LIVECDs.
It also provides fixed-sized output compression support, which improves
storage density, keeps relatively higher compression ratios, which is
more useful to achieve high performance for embedded devices with
limited  memory since it has unnoticable memory overhead and page cache
thrashing.

This commit adds support for three new filesystem targets:
erofs: erofs without compression
erofs-lz4: erofs with lz4 compresssion enabled
erofs-lz4hc: erofs with lz4hc compression enabled

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

4 files changed, 23 insertions, 7 deletions

diff --git a/scripts/lib/wic/help.py b/scripts/lib/wic/help.py
index bd3a2b97df..991e5094bb 100644
--- a/scripts/lib/wic/help.py
+++ b/scripts/lib/wic/help.py
@@ -930,6 +930,7 @@ DESCRIPTION
              ext4
              btrfs
              squashfs
+             erofs
              swap
 
          --fsoptions: Specifies a free-form string of options to be
diff --git a/scripts/lib/wic/ksparser.py b/scripts/lib/wic/ksparser.py
index 3eb669da39..7a4cc83af5 100644
--- a/scripts/lib/wic/ksparser.py
+++ b/scripts/lib/wic/ksparser.py
@@ -157,7 +157,8 @@ class KickStart():
         part.add_argument('--fsoptions', dest='fsopts')
         part.add_argument('--fstype', default='vfat',
                           choices=('ext2', 'ext3', 'ext4', 'btrfs',
-                                   'squashfs', 'vfat', 'msdos', 'swap'))
+                                   'squashfs', 'vfat', 'msdos', 'erofs',
+                                   'swap'))
         part.add_argument('--mkfs-extraopts', default='')
         part.add_argument('--label')
         part.add_argument('--use-label', action='store_true')
@@ -229,6 +230,10 @@ class KickStart():
                                 err = "%s:%d: SquashFS does not support LABEL" \
                                        % (confpath, lineno)
                                 raise KickStartError(err)
+                        # erofs does not support filesystem labels
+                        if parsed.fstype == 'erofs' and parsed.label:
+                            err = "%s:%d: erofs does not support LABEL" % (confpath, lineno)
+                            raise KickStartError(err)
                         if parsed.fstype == 'msdos' or parsed.fstype == 'vfat':
                             if parsed.fsuuid:
                                 if parsed.fsuuid.upper().startswith('0X'):
diff --git a/scripts/lib/wic/partition.py b/scripts/lib/wic/partition.py
index 76d144d12d..e0b2c5bdf2 100644
--- a/scripts/lib/wic/partition.py
+++ b/scripts/lib/wic/partition.py
@@ -141,9 +141,9 @@ class Partition():
                                             native_sysroot)
                 self.source_file = "%s/fs.%s" % (cr_workdir, self.fstype)
             else:
-                if self.fstype == 'squashfs':
-                    raise WicError("It's not possible to create empty squashfs "
-                                   "partition '%s'" % (self.mountpoint))
+                if self.fstype in ('squashfs', 'erofs'):
+                    raise WicError("It's not possible to create empty %s "
+                                   "partition '%s'" % (self.fstype, self.mountpoint))
 
                 rootfs = "%s/fs_%s.%s.%s" % (cr_workdir, self.label,
                                              self.lineno, self.fstype)
@@ -369,6 +369,16 @@ class Partition():
                        (rootfs_dir, rootfs, extraopts)
         exec_native_cmd(squashfs_cmd, native_sysroot, pseudo=pseudo)
 
+    def prepare_rootfs_erofs(self, rootfs, cr_workdir, oe_builddir, rootfs_dir,
+                             native_sysroot, pseudo):
+        """
+        Prepare content for a erofs rootfs partition.
+        """
+        extraopts = self.mkfs_extraopts or ''
+        erofs_cmd = "mkfs.erofs %s -U %s %s %s" % \
+                       (extraopts, self.fsuuid, rootfs, rootfs_dir)
+        exec_native_cmd(erofs_cmd, native_sysroot, pseudo=pseudo)
+
     def prepare_empty_partition_ext(self, rootfs, oe_builddir,
                                     native_sysroot):
         """
diff --git a/scripts/lib/wic/plugins/source/rawcopy.py b/scripts/lib/wic/plugins/source/rawcopy.py
index 3c4997d8ba..fa7b1eb8ac 100644
--- a/scripts/lib/wic/plugins/source/rawcopy.py
+++ b/scripts/lib/wic/plugins/source/rawcopy.py
@@ -29,9 +29,9 @@ class RawCopyPlugin(SourcePlugin):
             cmd = 'btrfs filesystem label %s %s' % (dst, label)
         elif fstype == 'swap':
             cmd = 'mkswap -L %s %s' % (label, dst)
-        elif fstype == 'squashfs':
-            raise WicError("It's not possible to update a squashfs "
-                           "filesystem label '%s'" % (label))
+        elif fstype in ('squashfs', 'erofs'):
+            raise WicError("It's not possible to update a %s "
+                           "filesystem label '%s'" % (fstype, label))
         else:
             raise WicError("Cannot update filesystem label: "
                            "Unknown fstype: '%s'" % (fstype))