image: add support for EROFS rootfs image

Add support for generating EROFS rootfs images.

The EROFS filesystem can offer competitive I/O performance while
minimizing final image size when using the MicroLZMA compressor.

Target platform: linux-x86_generic (target-i386_pentium4_musl)

Filesystem     Image Size
=============  ==========
root.erofs     4882432
root.ext4      109051904
root.squashfs  4903302

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

config/Config-build.in

@@ -384,6 +384,7 @@ menu "Global build settings"
 	config TARGET_ROOTFS_SECURITY_LABELS
 		bool
 		select KERNEL_SQUASHFS_XATTR
+		select KERNEL_EROFS_FS_SECURITY
 		select KERNEL_EXT4_FS_SECURITY
 		select KERNEL_F2FS_FS_SECURITY
 		select KERNEL_UBIFS_FS_SECURITY

config/Config-images.in

@@ -89,6 +89,23 @@ menu "Target Images"
 
 	comment "Root filesystem images"
 
+	menuconfig TARGET_ROOTFS_EROFS
+		bool "erofs"
+		default y if USES_EROFS
+		select KERNEL_EROFS_FS
+		help
+		  Build a EROFS root filesystem.
+
+		config TARGET_EROFS_PCLUSTER_SIZE
+			int "physical cluster size (in KiB)"
+			depends on TARGET_ROOTFS_EROFS
+			default 64 if LOW_MEMORY_FOOTPRINT
+			default 1024 if (SMALL_FLASH && !LOW_MEMORY_FOOTPRINT)
+			default 256
+			help
+			  Specify the EROFS physical cluster size (must be equal
+			  to or a multiple of the filesystem block size).
+
 	menuconfig TARGET_ROOTFS_EXT4FS
 		bool "ext4"
 		default y if USES_EXT4

config/Config-kernel.in

@@ -1305,6 +1305,23 @@ config KERNEL_BTRFS_FS
 	  Say Y here if you want to make the kernel to be able to boot off a
 	  BTRFS partition.
 
+config KERNEL_EROFS_FS
+	bool "Compile the kernel with built-in EROFS support"
+	help
+	  Say Y here if you want to make the kernel to be able to boot off a
+	  EROFS partition.
+
+config KERNEL_EROFS_FS_XATTR
+	bool "EROFS XATTR support"
+
+config KERNEL_EROFS_FS_ZIP
+	bool
+	default y if KERNEL_EROFS_FS
+
+config KERNEL_EROFS_FS_ZIP_LZMA
+	bool
+	default y if KERNEL_EROFS_FS
+
 menu "Filesystem ACL and attr support options"
 	config USE_FS_ACL_ATTR
 		bool "Use filesystem ACL and attr support by default"
@@ -1325,6 +1342,11 @@ menu "Filesystem ACL and attr support options"
 		select KERNEL_FS_POSIX_ACL
 		default y if USE_FS_ACL_ATTR
 
+	config KERNEL_EROFS_FS_POSIX_ACL
+		bool "Enable POSIX ACL for EROFS Filesystems"
+		select KERNEL_FS_POSIX_ACL
+		default y if USE_FS_ACL_ATTR
+
 	config KERNEL_EXT4_FS_POSIX_ACL
 		bool "Enable POSIX ACL for Ext4 Filesystems"
 		select KERNEL_FS_POSIX_ACL
@@ -1478,6 +1500,11 @@ config KERNEL_LSM
 	default "lockdown,yama,loadpin,safesetid,integrity,selinux"
 	depends on KERNEL_SECURITY_SELINUX
 
+config KERNEL_EROFS_FS_SECURITY
+	bool "EROFS Security Labels"
+	default y if !SMALL_FLASH
+	select KERNEL_EROFS_FS_XATTR
+
 config KERNEL_EXT4_FS_SECURITY
 	bool "Ext4 Security Labels"
 	default y if !SMALL_FLASH

include/image.mk

@@ -87,11 +87,21 @@ endif
 
 JFFS2_BLOCKSIZE ?= 64k 128k
 
+EROFS_PCLUSTERSIZE = $(shell echo $$(($(CONFIG_TARGET_EROFS_PCLUSTER_SIZE)*1024)))
+EROFSOPT := -Efragments,dedupe,ztailpacking -Uclear --all-root
+EROFSOPT += $(if $(SOURCE_DATE_EPOCH),-T$(SOURCE_DATE_EPOCH) --ignore-mtime)
+EROFSOPT += $(if $(CONFIG_SELINUX),,-x-1)
+EROFSCOMP := lz4hc,12
+ifeq ($(CONFIG_EROFS_FS_ZIP_LZMA),y)
+EROFSCOMP := lzma,109
+endif
+
 fs-types-$(CONFIG_TARGET_ROOTFS_SQUASHFS) += squashfs
 fs-types-$(CONFIG_TARGET_ROOTFS_JFFS2) += $(addprefix jffs2-,$(JFFS2_BLOCKSIZE))
 fs-types-$(CONFIG_TARGET_ROOTFS_JFFS2_NAND) += $(addprefix jffs2-nand-,$(NAND_BLOCKSIZE))
 fs-types-$(CONFIG_TARGET_ROOTFS_EXT4FS) += ext4
 fs-types-$(CONFIG_TARGET_ROOTFS_UBIFS) += ubifs
+fs-types-$(CONFIG_TARGET_ROOTFS_EROFS) += erofs
 fs-subtypes-$(CONFIG_TARGET_ROOTFS_JFFS2) += $(addsuffix -raw,$(addprefix jffs2-,$(JFFS2_BLOCKSIZE)))
 
 TARGET_FILESYSTEMS := $(fs-types-y)
@@ -275,6 +285,13 @@ define Image/mkfs/ext4
 		$@ $(call mkfs_target_dir,$(1))/
 endef
 
+# Don't use the mkfs.erofs builtin $SOURCE_DATE_EPOCH behavior
+define Image/mkfs/erofs
+	env -u SOURCE_DATE_EPOCH $(STAGING_DIR_HOST)/bin/mkfs.erofs -z$(EROFSCOMP) \
+		-C$(EROFS_PCLUSTERSIZE) $(EROFSOPT) \
+		$@ $(call mkfs_target_dir,$(1))
+endef
+
 define Image/Manifest
 	$(call opkg,$(TARGET_DIR_ORIG)) list-installed > \
 		$(BIN_DIR)/$(IMG_PREFIX)$(if $(PROFILE_SANITIZED),-$(PROFILE_SANITIZED)).manifest

package/system/fstools/patches/0001-EroFS.patch

@@ -0,0 +1,139 @@
+From e8cd820cdbb8fba990fd79efda90c5dc10d8e45c Mon Sep 17 00:00:00 2001
+From: Gao Xiang <xiang@kernel.org>
+Subject: [PATCH] libfstools: add support for EroFS based images
+
+Add support to libfstools to parse and support EroFS based images to
+permit correct mounting of OverlayFS with it. (in addition to SquashFS
+support)
+
+While at it rework the code to better handle the 2 different filesystem
+introducing a similar pattern.
+
+Signed-off-by: Gao Xiang <xiang@kernel.org>
+Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
+---
+ libfstools/rootdisk.c | 83 +++++++++++++++++++++++++++++++++++++++----
+ 1 file changed, 77 insertions(+), 6 deletions(-)
+
+--- a/libfstools/rootdisk.c
++++ b/libfstools/rootdisk.c
+@@ -15,6 +15,8 @@
+ 
+ #include <linux/loop.h>
+ 
++#define SQUASHFS_MAGIC		"hsqs"
++#define EROFS_MAGIC		0xE0F5E1E2
+ #define ROOTDEV_OVERLAY_ALIGN	(64ULL * 1024ULL)
+ #define F2FS_MINSIZE		(100ULL * 1024ULL * 1024ULL)
+ 
+@@ -24,6 +26,14 @@ struct squashfs_super_block {
+ 	uint64_t bytes_used;
+ };
+ 
++struct erofs_super_block {
++	uint32_t s_magic;
++	uint32_t pad0[2];
++	uint8_t blkszbits;
++	uint8_t pad1[23];
++	uint32_t blocks;
++};
++
+ struct rootdev_volume {
+ 	struct volume v;
+ 	uint64_t offset;
+@@ -93,10 +103,66 @@ static int get_squashfs(struct squashfs_
+ 	return 0;
+ }
+ 
+-static struct volume *rootdisk_volume_find(char *name)
++static int check_squashfs(uint64_t *offset)
+ {
++	const char *s_magic = SQUASHFS_MAGIC;
+ 	struct squashfs_super_block sb;
++	int ret;
++
++	ret = get_squashfs(&sb);
++	if (ret)
++		return ret;
++
++	if (memcmp(&sb.s_magic, s_magic, sizeof(sb.s_magic)))
++		return -1;
++
++	*offset = le64_to_cpu(sb.bytes_used);
++	return 0;
++}
++
++static int get_erofs(struct erofs_super_block *sb)
++{
++	FILE *f;
++	int len;
++
++	f = fopen(rootdev, "r");
++	if (!f)
++		return -1;
++
++	if (fseek(f, 1024, SEEK_SET))
++		return -1;
++
++	len = fread(sb, sizeof(*sb), 1, f);
++	fclose(f);
++
++	if (len != 1)
++		return -1;
++
++	return 0;
++}
++
++static int check_erofs(uint64_t *offset)
++{
++	uint32_t s_magic = cpu_to_le32(EROFS_MAGIC);
++	struct erofs_super_block sb;
++	int ret;
++
++	ret = get_erofs(&sb);
++	if (ret)
++		return ret;
++
++	if (memcmp(&sb.s_magic, &s_magic, sizeof(sb.s_magic)))
++		return -1;
++
++	*offset = (uint64_t)le32_to_cpu(sb.blocks) << sb.blkszbits;
++	return 0;
++}
++
++static struct volume *rootdisk_volume_find(char *name)
++{
+ 	struct rootdev_volume *p;
++	uint64_t offset;
++	int ret;
+ 
+ 	if (strcmp(name, "rootfs_data") != 0)
+ 		return NULL;
+@@ -108,17 +174,22 @@ static struct volume *rootdisk_volume_fi
+ 	if (!rootdev)
+ 		return NULL;
+ 
+-	if (get_squashfs(&sb))
+-		return NULL;
+-
+-	if (memcmp(&sb.s_magic, "hsqs", sizeof(sb.s_magic)) != 0)
++	/*
++	 * We support both SquashFS and EroFS.
++	 * First check for SquashFS and then check
++	 * for EroFS on new images.
++	 */
++	ret = check_squashfs(&offset);
++	if (ret < 0 || !offset)
++		ret = check_erofs(&offset);
++	if (ret < 0 || !offset)
+ 		return NULL;
+ 
+ 	p = calloc(1, sizeof(*p));
+ 	p->v.drv = &rootdisk_driver;
+ 	p->v.name = "rootfs_data";
+ 
+-	p->offset = le64_to_cpu(sb.bytes_used);
++	p->offset = offset;
+ 	p->offset = ((p->offset + (ROOTDEV_OVERLAY_ALIGN - 1)) &
+ 		     ~(ROOTDEV_OVERLAY_ALIGN - 1));
+ 

scripts/target-metadata.pl

@@ -18,6 +18,7 @@ sub target_config_features(@) {
 		/^dt$/ and $ret .= "\tselect USES_DEVICETREE\n";
 		/^dt-overlay$/ and $ret .= "\tselect HAS_DT_OVERLAY_SUPPORT\n";
 		/^emmc$/ and $ret .= "\tselect EMMC_SUPPORT\n";
+		/^erofs$/ and $ret .= "\tselect USES_EROFS\n";
 		/^ext4$/ and $ret .= "\tselect USES_EXT4\n";
 		/^fpu$/ and $ret .= "\tselect HAS_FPU\n";
 		/^gpio$/ and $ret .= "\tselect GPIO_SUPPORT\n";

target/Config.in

@@ -69,6 +69,9 @@ config USES_JFFS2_NAND
 config USES_EXT4
 	bool
 
+config USES_EROFS
+	bool
+
 config USES_TARGZ
 	bool
 

target/linux/generic/config-6.1

@@ -1978,6 +1978,12 @@ CONFIG_ENABLE_WARN_DEPRECATED=y
 CONFIG_EPOLL=y
 # CONFIG_EQUALIZER is not set
 # CONFIG_EROFS_FS is not set
+# CONFIG_EROFS_FS_DEBUG is not set
+# CONFIG_EROFS_FS_XATTR is not set
+# CONFIG_EROFS_FS_POSIX_ACL is not set
+# CONFIG_EROFS_FS_SECURITY is not set
+# CONFIG_EROFS_FS_ZIP is not set
+# CONFIG_EROFS_FS_ONDEMAND is not set
 # CONFIG_ET131X is not set
 CONFIG_ETHERNET=y
 # CONFIG_ETHOC is not set

target/linux/generic/config-6.12

@@ -1896,6 +1896,17 @@ CONFIG_ELFCORE=y
 CONFIG_EPOLL=y
 # CONFIG_EQUALIZER is not set
 # CONFIG_EROFS_FS is not set
+# CONFIG_EROFS_FS_DEBUG is not set
+# CONFIG_EROFS_FS_XATTR is not set
+# CONFIG_EROFS_FS_POSIX_ACL is not set
+# CONFIG_EROFS_FS_SECURITY is not set
+# CONFIG_EROFS_FS_BACKED_BY_FILE is not set
+# CONFIG_EROFS_FS_ZIP is not set
+# CONFIG_EROFS_FS_ZIP_DEFLATE is not set
+# CONFIG_EROFS_FS_ZIP_ZSTD is not set
+# CONFIG_EROFS_FS_ONDEMAND is not set
+CONFIG_EROFS_FS_PCPU_KTHREAD=y
+CONFIG_EROFS_FS_PCPU_KTHREAD_HIPRI=y
 # CONFIG_ET131X is not set
 CONFIG_ETHERNET=y
 # CONFIG_ETHOC is not set

target/linux/generic/config-6.6

@@ -1840,6 +1840,15 @@ CONFIG_ELFCORE=y
 CONFIG_EPOLL=y
 # CONFIG_EQUALIZER is not set
 # CONFIG_EROFS_FS is not set
+# CONFIG_EROFS_FS_DEBUG is not set
+# CONFIG_EROFS_FS_XATTR is not set
+# CONFIG_EROFS_FS_POSIX_ACL is not set
+# CONFIG_EROFS_FS_SECURITY is not set
+# CONFIG_EROFS_FS_ZIP is not set
+# CONFIG_EROFS_FS_ZIP_DEFLATE is not set
+# CONFIG_EROFS_FS_ONDEMAND is not set
+CONFIG_EROFS_FS_PCPU_KTHREAD=y
+CONFIG_EROFS_FS_PCPU_KTHREAD_HIPRI=y
 # CONFIG_ET131X is not set
 CONFIG_ETHERNET=y
 # CONFIG_ETHOC is not set