util-linux: support erofs filesystem

Add erofs to the known volume_ids.

function                                             old     new   delta
volume_id_probe_erofs                                  -      89     +89
fs1                                                   24      28      +4
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 1/0 up/down: 93/0)               Total: 93 bytes

Signed-off-by: Norbert Lange <nolange79@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 72 insertions, 0 deletions

diff --git a/util-linux/volume_id/erofs.c b/util-linux/volume_id/erofs.c
new file mode 100644
index 000000000..a163a353d
--- /dev/null
+++ b/util-linux/volume_id/erofs.c
@@ -0,0 +1,67 @@
+/*
+ * volume_id - reads filesystem label and uuid
+ *
+ * Copyright (C) 2020 Norbert Lange <nolange79@gmail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+//config:config FEATURE_VOLUMEID_EROFS
+//config:       bool "erofs filesystem"
+//config:       default y
+//config:       depends on VOLUMEID
+//config:       help
+//config:       Erofs is a compressed readonly filesystem for Linux.
+
+//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_EROFS) += erofs.o
+
+#include "volume_id_internal.h"
+
+#define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
+#define EROFS_SUPER_OFFSET      1024
+#define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
+
+/* 128-byte erofs on-disk super block */
+struct erofs_super_block {
+        uint32_t magic;           /* file system magic number */
+        uint32_t checksum;        /* crc32c(super_block) */
+        uint32_t feature_compat;
+        uint8_t blkszbits;         /* support block_size == PAGE_SIZE only */
+        uint8_t reserved;
+
+        uint16_t root_nid;      /* nid of root directory */
+        uint64_t inos;            /* total valid ino # (== f_files - f_favail) */
+
+        uint64_t build_time;      /* inode v1 time derivation */
+        uint32_t build_time_nsec;       /* inode v1 time derivation in nano scale */
+        uint32_t blocks;          /* used for statfs */
+        uint32_t meta_blkaddr;  /* start block address of metadata area */
+        uint32_t xattr_blkaddr; /* start block address of shared xattr area */
+        uint8_t uuid[16];          /* 128-bit uuid for volume */
+        uint8_t volume_name[16];   /* volume name */
+        uint32_t feature_incompat;
+        uint8_t reserved2[44];
+} PACKED;
+
+int FAST_FUNC volume_id_probe_erofs(struct volume_id *id /*,uint64_t off*/)
+{
+        struct erofs_super_block *sb;
+
+        BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
+
+        dbg("erofs: probing at offset 0x%llx", EROFS_SUPER_OFFSET);
+        sb = volume_id_get_buffer(id, EROFS_SUPER_OFFSET, sizeof(*sb));
+        if (!sb)
+                return -1;
+
+        if (sb->magic != cpu_to_le32(EROFS_SUPER_MAGIC_V1))
+                return -1;
+
+        IF_FEATURE_BLKID_TYPE(id->type = "erofs");
+
+        volume_id_set_label_string(id, sb->volume_name,
+                MIN(sizeof(sb->volume_name), VOLUME_ID_LABEL_SIZE));
+
+        volume_id_set_uuid(id, sb->uuid, UUID_DCE);
+
+        return 0;
+}
diff --git a/util-linux/volume_id/volume_id.c b/util-linux/volume_id/volume_id.c
index c3f07a741..99150a5b7 100644
--- a/util-linux/volume_id/volume_id.c
+++ b/util-linux/volume_id/volume_id.c
@@ -106,6 +106,9 @@ static const probe_fptr fs1[] = {
 #if ENABLE_FEATURE_VOLUMEID_SQUASHFS
         volume_id_probe_squashfs,
 #endif
+#if ENABLE_FEATURE_VOLUMEID_EROFS
+        volume_id_probe_erofs,
+#endif
 #if ENABLE_FEATURE_VOLUMEID_XFS
         volume_id_probe_xfs,
 #endif
diff --git a/util-linux/volume_id/volume_id_internal.h b/util-linux/volume_id/volume_id_internal.h
index ada18339d..609beb84e 100644
--- a/util-linux/volume_id/volume_id_internal.h
+++ b/util-linux/volume_id/volume_id_internal.h
@@ -215,6 +215,8 @@ int FAST_FUNC volume_id_probe_romfs(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_squashfs(struct volume_id *id /*,uint64_t off*/);
 
+int FAST_FUNC volume_id_probe_erofs(struct volume_id *id /*,uint64_t off*/);
+
 int FAST_FUNC volume_id_probe_sysv(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_udf(struct volume_id *id /*,uint64_t off*/);