erofs-utils: mkfs: support flatdev for multi-blob images

Since kernel commit 8b465fecc35a ("erofs: support flattened block device
for multi-blob images"), the flatdev feature has been introduced to
support mounting multi-blobs container image as a single block device.

To enable this feature, the mapped_blkaddr of each device slot needs to
be set properly to the offset of the device in the flat address space.

The uuid of the source image is used as the corresponding device tag
in rebuild mode.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230915115333.17599-1-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

4 files changed, 31 insertions, 6 deletions

diff --git a/include/erofs/internal.h b/include/erofs/internal.h
index 19b912b..616cd3a 100644
--- a/include/erofs/internal.h
+++ b/include/erofs/internal.h
@@ -54,6 +54,7 @@ extern struct erofs_sb_info sbi;
 struct erofs_buffer_head;
 
 struct erofs_device_info {
+	u8 tag[64];
 	u32 blocks;
 	u32 mapped_blkaddr;
 };
diff --git a/lib/blobchunk.c b/lib/blobchunk.c
index aca616e..a599f3a 100644
--- a/lib/blobchunk.c
+++ b/lib/blobchunk.c
@@ -410,20 +410,24 @@ int erofs_mkfs_dump_blobs(struct erofs_sb_info *sbi)
 	}
 
 	if (sbi->extra_devices) {
-		unsigned int i;
+		unsigned int i, ret;
+		erofs_blk_t nblocks;
 
+		nblocks = erofs_mapbh(NULL);
 		pos_out = erofs_btell(bh_devt, false);
 		i = 0;
 		do {
 			struct erofs_deviceslot dis = {
+				.mapped_blkaddr = cpu_to_le32(nblocks),
 				.blocks = cpu_to_le32(sbi->devs[i].blocks),
 			};
-			int ret;
 
+			memcpy(dis.tag, sbi->devs[i].tag, sizeof(dis.tag));
 			ret = dev_write(sbi, &dis, pos_out, sizeof(dis));
 			if (ret)
 				return ret;
 			pos_out += sizeof(dis);
+			nblocks += sbi->devs[i].blocks;
 		} while (++i < sbi->extra_devices);
 		bh_devt->op = &erofs_drop_directly_bhops;
 		erofs_bdrop(bh_devt, false);
diff --git a/lib/super.c b/lib/super.c
index ce97278..f952f7e 100644
--- a/lib/super.c
+++ b/lib/super.c
@@ -65,6 +65,7 @@ static int erofs_init_devices(struct erofs_sb_info *sbi,
 
 		sbi->devs[i].mapped_blkaddr = le32_to_cpu(dis.mapped_blkaddr);
 		sbi->devs[i].blocks = le32_to_cpu(dis.blocks);
+		memcpy(sbi->devs[i].tag, dis.tag, sizeof(dis.tag));
 		sbi->total_blocks += sbi->devs[i].blocks;
 		pos += EROFS_DEVT_SLOT_SIZE;
 	}
diff --git a/mkfs/main.c b/mkfs/main.c
index 4fa2d92..a765743 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -822,7 +822,7 @@ static int erofs_rebuild_load_trees(struct erofs_inode *root)
 	struct erofs_sb_info *src;
 	unsigned int extra_devices = 0;
 	erofs_blk_t nblocks;
-	int ret;
+	int ret, idx;
 
 	list_for_each_entry(src, &rebuild_src_list, list) {
 		ret = erofs_rebuild_load_tree(root, src);
@@ -849,12 +849,31 @@ static int erofs_rebuild_load_trees(struct erofs_inode *root)
 		return ret;
 
 	list_for_each_entry(src, &rebuild_src_list, list) {
-		if (extra_devices)
+		u8 *tag = NULL;
+
+		if (extra_devices) {
 			nblocks = src->devs[0].blocks;
-		else
+			tag = src->devs[0].tag;
+		} else {
 			nblocks = src->primarydevice_blocks;
+		}
 		DBG_BUGON(src->dev < 1);
-		sbi.devs[src->dev - 1].blocks = nblocks;
+		idx = src->dev - 1;
+		sbi.devs[idx].blocks = nblocks;
+		if (tag && *tag)
+			memcpy(sbi.devs[idx].tag, tag, sizeof(sbi.devs[0].tag));
+		else
+			/* convert UUID of the source image to a hex string */
+			sprintf((char *)sbi.devs[idx].tag,
+				"%04x%04x%04x%04x%04x%04x%04x%04x",
+				(src->uuid[0] << 8) | src->uuid[1],
+				(src->uuid[2] << 8) | src->uuid[3],
+				(src->uuid[4] << 8) | src->uuid[5],
+				(src->uuid[6] << 8) | src->uuid[7],
+				(src->uuid[8] << 8) | src->uuid[9],
+				(src->uuid[10] << 8) | src->uuid[11],
+				(src->uuid[12] << 8) | src->uuid[13],
+				(src->uuid[14] << 8) | src->uuid[15]);
 	}
 	return 0;
 }