[PATCH] mkfs: support block map for blob devices

[PATCH] mkfs: support block map for blob devices

[Nithurshen]

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 that blocked this combination of flags.
	2) Calculating the global startblk address for the block map by summing the blocks of the primary device and any preceding extra devices.
	3) Ensuring that EROFS_CHUNK_FORMAT_INDEXES is only set if the user has not forced the block map format, and adjusting the index unit size to EROFS_BLOCK_MAP_ENTRY_SIZE accordingly.
	4) Updating erofs_inode_fixup_chunkformat to correctly identify when 48-bit addressing is required for a block-mapped file on an extra device.

Signed-off-by: Nithurshen <nithurshen.dev@gmail.com>
---
 lib/blobchunk.c | 34 ++++++++++++++++++++++++++++------
 mkfs/main.c     |  7 -------
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/lib/blobchunk.c b/lib/blobchunk.c
index 96c161b..2ef7462 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) {
+					_48bit = true;
+					break;
+				}
+			} 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/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

Re: [PATCH] mkfs: support block map for blob devices

[zhaoyifan (H)]

On 2026/3/7 14:28, Nithurshen wrote:
> 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 that blocked this combination of flags.
> 	2) Calculating the global startblk address for the block map by summing the blocks of the primary device and any preceding extra devices.
> 	3) Ensuring that EROFS_CHUNK_FORMAT_INDEXES is only set if the user has not forced the block map format, and adjusting the index unit size to EROFS_BLOCK_MAP_ENTRY_SIZE accordingly.
> 	4) Updating erofs_inode_fixup_chunkformat to correctly identify when 48-bit addressing is required for a block-mapped file on an extra device.

Hi Nithurshen,

Each line of the commit message must not exceed 72 characters.

> Signed-off-by: Nithurshen <nithurshen.dev@gmail.com>
> ---
>   lib/blobchunk.c | 34 ++++++++++++++++++++++++++++------
>   mkfs/main.c     |  7 -------
>   2 files changed, 28 insertions(+), 13 deletions(-)
>
> diff --git a/lib/blobchunk.c b/lib/blobchunk.c
> index 96c161b..2ef7462 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) {
> +					_48bit = true;

It's impossible for 32-bit block map entries to support 48bit mode.

I think we should err out instead of enabling 48bit here.


BTW, it seems the erofs-utils codebase could not read a chunk-based 
EROFS image

with block map and extra devices (but in-kernel implementation could), 
as erofs_map_dev() does

not reset m_deviceid. Could you help also fix this? If you are 
interested please also add related

testcases in erofs/erofsnightly repo.


Thanks,

Yifan Zhao

> +					break;
> +				}
> +			} 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/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;

Re: [PATCH] mkfs: support block map for blob devices

[Nithurshen Karthikeyan]

Hi Yifan Zhao,

> Hi Nithurshen,
>
> Each line of the commit message must not exceed 72 characters.

I don't know how it went wrong, but I will double check from this time.

> It's impossible for 32-bit block map entries to support 48bit mode.
>
> I think we should err out instead of enabling 48bit here.
>
>
> BTW, it seems the erofs-utils codebase could not read a chunk-based
> EROFS image
>
> with block map and extra devices (but in-kernel implementation could),
> as erofs_map_dev() does
>

I have taken care of this in v2 Patch.

> Could you help also fix this? If you are
> interested please also add related
>
> testcases in erofs/erofsnightly repo.

Sure. I am interested.
I will work on it shortly.

Thanks and regards
Nithurshen

Re: [PATCH] mkfs: support block map for blob devices

[Nithurshen Karthikeyan]

[-- Attachment #1: Type: text/plain, Size: 378 bytes --]

Hi Yifan Zhao,

On Mon, Mar 9, 2026 at 5:08 PM zhaoyifan (H) <zhaoyifan28@huawei.com> wrote:
> not reset m_deviceid. Could you help also fix this? If you are
> interested please also add related
>
> testcases in erofs/erofsnightly repo.

I have opened PR #7 in erofs/erofsnightly repo.
https://github.com/erofs/erofsnightly/pull/7

Thanks and regards,
Nithurshen

[-- Attachment #2: Type: text/html, Size: 544 bytes --]

Re: [PATCH] mkfs: support block map for blob devices

[Gao Xiang]

On 2026/3/12 17:56, Nithurshen Karthikeyan wrote:
> Hi Yifan Zhao,
> 
> On Mon, Mar 9, 2026 at 5:08 PM zhaoyifan (H) <zhaoyifan28@huawei.com> wrote:
>> not reset m_deviceid. Could you help also fix this? If you are
>> interested please also add related
>>
>> testcases in erofs/erofsnightly repo.
> 
> I have opened PR #7 in erofs/erofsnightly repo.
> https://github.com/erofs/erofsnightly/pull/7

Such test cases should be landed in experimental-tests
instead rather than integration tests (erofsnightly).

I will check out later, busying in other stuffs.

Thanks,
Gao Xiang

> 
> Thanks and regards,
> Nithurshen
> 

Re: [PATCH] mkfs: support block map for blob devices

[Nithurshen Karthikeyan]

On Thu, Mar 12, 2026 at 5:10 PM Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
>
>
>
> On 2026/3/12 17:56, Nithurshen Karthikeyan wrote:
> > Hi Yifan Zhao,
> >
> > On Mon, Mar 9, 2026 at 5:08 PM zhaoyifan (H) <zhaoyifan28@huawei.com> wrote:
> >> not reset m_deviceid. Could you help also fix this? If you are
> >> interested please also add related
> >>
> >> testcases in erofs/erofsnightly repo.
> >
> > I have opened PR #7 in erofs/erofsnightly repo.
> > https://github.com/erofs/erofsnightly/pull/7
>
> Such test cases should be landed in experimental-tests
> instead rather than integration tests (erofsnightly).
>

I placed it to erofsnightly because, I was specifically told to by Yifan Zhao.
I will send a patch to experimental-tests branch shortly.

> I will check out later, busying in other stuffs.

Sure, you can review it when you have time.

> Thanks,
> Gao Xiang
>
> >
> > Thanks and regards,
> > Nithurshen
> >
>

Re: [PATCH] mkfs: support block map for blob devices

[Nithurshen Karthikeyan]

Hi Xiang,

On Thu, Mar 12, 2026 at 5:10 PM Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> Such test cases should be landed in experimental-tests
> instead rather than integration tests (erofsnightly).

I have sent a patch for `experimental-tests` branch adding test-028.

Thanks and Regards
Nithurshen

[PATCH v2] mkfs: support block map for blob devices

[Nithurshen]

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 <nithurshen.dev@gmail.com>
---
 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