Currently, using --blobdev to specify an extra device is restricted
from working with the block map chunk format. This was previously
noted as a task that could be implemented by mapping the device
blocks using a global address.

This patch implements this support by allowing the block map to
reference chunks residing on extra devices. This is achieved by:
1) Removing the -EINVAL check in mkfs/main.c.
2) Calculating the global startblk address for the block map by
   summing the blocks of the primary device and preceding devices.
3) Ensuring EROFS_CHUNK_FORMAT_INDEXES is only set if the user
   has not forced the block map format.
4) Updating erofs_inode_fixup_chunkformat to error out if the
   mapped address exceeds UINT32_MAX, as block maps cannot
   support 48-bit addressing.

In addition, erofs_map_dev() is updated to correctly identify the
device ID when a global block address is used with block maps,
enabling userspace tools to read these images.

Signed-off-by: Nithurshen <[email protected]>
---
 lib/blobchunk.c | 34 ++++++++++++++++++++++++++++------
 lib/data.c      |  1 +
 mkfs/main.c     |  7 -------
 3 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/lib/blobchunk.c b/lib/blobchunk.c
index 96c161b..fdcf4b3 100644
--- a/lib/blobchunk.c
+++ b/lib/blobchunk.c
@@ -159,7 +159,17 @@ void erofs_inode_fixup_chunkformat(struct erofs_inode 
*inode)
                if (chunk->blkaddr == EROFS_NULL_ADDR)
                        continue;
                if (chunk->device_id) {
-                       if (chunk->blkaddr > UINT32_MAX) {
+                       if (!(inode->u.chunkformat & 
EROFS_CHUNK_FORMAT_INDEXES)) {
+                               erofs_blk_t mapped_blkaddr = 
inode->sbi->primarydevice_blocks;
+                               unsigned int i;
+
+                               for (i = 0; i < chunk->device_id - 1; i++)
+                                       mapped_blkaddr += 
inode->sbi->devs[i].blocks;
+                               if (mapped_blkaddr + chunk->blkaddr > 
UINT32_MAX) {
+                                       erofs_err("block map cannot support 
addresses > UINT32_MAX");
+                                       return;
+                               }
+                       } else if (chunk->blkaddr > UINT32_MAX) {
                                _48bit = true;
                                break;
                        }
@@ -201,8 +211,16 @@ int erofs_write_chunk_indexes(struct erofs_inode *inode, 
struct erofs_vfile *vf,
                if (chunk->blkaddr == EROFS_NULL_ADDR) {
                        startblk = EROFS_NULL_ADDR;
                } else if (chunk->device_id) {
-                       DBG_BUGON(!(inode->u.chunkformat & 
EROFS_CHUNK_FORMAT_INDEXES));
-                       startblk = chunk->blkaddr;
+                       if (inode->u.chunkformat & EROFS_CHUNK_FORMAT_INDEXES) {
+                               startblk = chunk->blkaddr;
+                       } else {
+                               unsigned int i;
+
+                               startblk = sbi->primarydevice_blocks;
+                               for (i = 0; i < chunk->device_id - 1; i++)
+                                       startblk += sbi->devs[i].blocks;
+                               startblk += chunk->blkaddr;
+                       }
                        extent_start = EROFS_NULL_ADDR;
                } else {
                        startblk = remapped_base + chunk->blkaddr;
@@ -324,7 +342,7 @@ int erofs_blob_write_chunked_file(struct erofs_inode 
*inode, int fd,
        chunksize = 1ULL << chunkbits;
        count = DIV_ROUND_UP(inode->i_size, chunksize);
 
-       if (sbi->extra_devices)
+       if (sbi->extra_devices && cfg.c_force_chunkformat != 
FORCE_INODE_BLOCK_MAP)
                inode->u.chunkformat |= EROFS_CHUNK_FORMAT_INDEXES;
        if (inode->u.chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
                unit = sizeof(struct erofs_inode_chunk_index);
@@ -494,8 +512,12 @@ int tarerofs_write_chunkes(struct erofs_inode *inode, 
erofs_off_t data_offset)
        inode->u.chunkformat |= chunkbits - sbi->blkszbits;
        if (sbi->extra_devices) {
                device_id = 1;
-               inode->u.chunkformat |= EROFS_CHUNK_FORMAT_INDEXES;
-               unit = sizeof(struct erofs_inode_chunk_index);
+               if (cfg.c_force_chunkformat != FORCE_INODE_BLOCK_MAP)
+                       inode->u.chunkformat |= EROFS_CHUNK_FORMAT_INDEXES;
+               if (inode->u.chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
+                       unit = sizeof(struct erofs_inode_chunk_index);
+               else
+                       unit = EROFS_BLOCK_MAP_ENTRY_SIZE;
                DBG_BUGON(erofs_blkoff(sbi, data_offset));
                blkaddr = erofs_blknr(sbi, data_offset);
        } else {
diff --git a/lib/data.c b/lib/data.c
index 6fd1389..5aeb0c1 100644
--- a/lib/data.c
+++ b/lib/data.c
@@ -184,6 +184,7 @@ int erofs_map_dev(struct erofs_sb_info *sbi, struct 
erofs_map_dev *map)
                        if (map->m_pa >= startoff &&
                            map->m_pa < startoff + length) {
                                map->m_pa -= startoff;
+                               map->m_deviceid = id + 1;
                                break;
                        }
                }
diff --git a/mkfs/main.c b/mkfs/main.c
index 58c18f9..07ef086 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -1565,13 +1565,6 @@ static int mkfs_parse_options_cfg(struct 
erofs_importer_params *params,
                return -EINVAL;
        }
 
-       /* TODO: can be implemented with (deviceslot) mapped_blkaddr */
-       if (cfg.c_blobdev_path &&
-           cfg.c_force_chunkformat == FORCE_INODE_BLOCK_MAP) {
-               erofs_err("--blobdev cannot work with block map currently");
-               return -EINVAL;
-       }
-
        if (optind >= argc) {
                erofs_err("missing argument: FILE");
                return -EINVAL;
-- 
2.51.0


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