1 files changed, 105 insertions, 0 deletions
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
new file mode 100644
index 0000000000..4cca322b9e
--- /dev/null
+++ b/fs/erofs/super.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include "internal.h"
+
+static bool check_layout_compatibility(struct erofs_sb_info *sbi,
+				       struct erofs_super_block *dsb)
+{
+	const unsigned int feature = le32_to_cpu(dsb->feature_incompat);
+
+	sbi->feature_incompat = feature;
+
+	/* check if current kernel meets all mandatory requirements */
+	if (feature & (~EROFS_ALL_FEATURE_INCOMPAT)) {
+		erofs_err("unidentified incompatible feature %x, please upgrade kernel version",
+			  feature & ~EROFS_ALL_FEATURE_INCOMPAT);
+		return false;
+	}
+	return true;
+}
+
+static int erofs_init_devices(struct erofs_sb_info *sbi,
+			      struct erofs_super_block *dsb)
+{
+	unsigned int ondisk_extradevs, i;
+	erofs_off_t pos;
+
+	sbi->total_blocks = sbi->primarydevice_blocks;
+
+	if (!erofs_sb_has_device_table())
+		ondisk_extradevs = 0;
+	else
+		ondisk_extradevs = le16_to_cpu(dsb->extra_devices);
+
+	if (ondisk_extradevs != sbi->extra_devices) {
+		erofs_err("extra devices don't match (ondisk %u, given %u)",
+			  ondisk_extradevs, sbi->extra_devices);
+		return -EINVAL;
+	}
+	if (!ondisk_extradevs)
+		return 0;
+
+	sbi->device_id_mask = roundup_pow_of_two(ondisk_extradevs + 1) - 1;
+	sbi->devs = calloc(ondisk_extradevs, sizeof(*sbi->devs));
+	pos = le16_to_cpu(dsb->devt_slotoff) * EROFS_DEVT_SLOT_SIZE;
+	for (i = 0; i < ondisk_extradevs; ++i) {
+		struct erofs_deviceslot dis;
+		int ret;
+
+		ret = erofs_dev_read(0, &dis, pos, sizeof(dis));
+		if (ret < 0)
+			return ret;
+
+		sbi->devs[i].mapped_blkaddr = dis.mapped_blkaddr;
+		sbi->total_blocks += dis.blocks;
+		pos += EROFS_DEVT_SLOT_SIZE;
+	}
+	return 0;
+}
+
+int erofs_read_superblock(void)
+{
+	char data[EROFS_BLKSIZ];
+	struct erofs_super_block *dsb;
+	unsigned int blkszbits;
+	int ret;
+
+	ret = erofs_blk_read(data, 0, 1);
+	if (ret < 0) {
+		erofs_err("cannot read erofs superblock: %d", ret);
+		return -EIO;
+	}
+	dsb = (struct erofs_super_block *)(data + EROFS_SUPER_OFFSET);
+
+	ret = -EINVAL;
+	if (le32_to_cpu(dsb->magic) != EROFS_SUPER_MAGIC_V1) {
+		erofs_err("cannot find valid erofs superblock");
+		return ret;
+	}
+
+	sbi.feature_compat = le32_to_cpu(dsb->feature_compat);
+
+	blkszbits = dsb->blkszbits;
+	/* 9(512 bytes) + LOG_SECTORS_PER_BLOCK == LOG_BLOCK_SIZE */
+	if (blkszbits != LOG_BLOCK_SIZE) {
+		erofs_err("blksize %u isn't supported on this platform",
+			  1 << blkszbits);
+		return ret;
+	}
+
+	if (!check_layout_compatibility(&sbi, dsb))
+		return ret;
+
+	sbi.primarydevice_blocks = le32_to_cpu(dsb->blocks);
+	sbi.meta_blkaddr = le32_to_cpu(dsb->meta_blkaddr);
+	sbi.xattr_blkaddr = le32_to_cpu(dsb->xattr_blkaddr);
+	sbi.islotbits = EROFS_ISLOTBITS;
+	sbi.root_nid = le16_to_cpu(dsb->root_nid);
+	sbi.inos = le64_to_cpu(dsb->inos);
+	sbi.checksum = le32_to_cpu(dsb->checksum);
+
+	sbi.build_time = le64_to_cpu(dsb->build_time);
+	sbi.build_time_nsec = le32_to_cpu(dsb->build_time_nsec);
+
+	memcpy(&sbi.uuid, dsb->uuid, sizeof(dsb->uuid));
+	return erofs_init_devices(&sbi, dsb);
+}