[PATCH v2] erofs-utils: lib: fix 48bit addressing detection for chunk-based format

[Gao Xiang]

On 2026/2/25 00:37, puneeth_aditya_5656 wrote:
> The 48-bit chunk format flag was being set inside
> erofs_blob_write_chunked_file right after erofs_blob_getchunk returns.
> At that point chunk->blkaddr is the chunk's offset in the temporary
> blob buffer, not the final image address. The real address is only
> known after erofs_mkfs_dump_blobs applies remapped_base.
> 
> This means the detection was unreliable in both directions: a chunk
> whose blob offset looks large but fits in 32-bits after remapping gets
> flagged unnecessarily, and worse, a chunk that lands above UINT32_MAX
> after remapping may not get flagged at all, producing a corrupt image.
> 
> Fix this by introducing erofs_inode_fixup_chunkformat() which walks
> the chunk array after remapped_base is finalized and sets the 48-bit
> flag if any chunk address exceeds UINT32_MAX. The fixup is called from
> erofs_bh_flush_write_inode before erofs_iflush so that the correct
> chunkformat is written into the on-disk inode header. Both blob chunks
> (remapped_base + chunk->blkaddr) and device chunks (chunk->blkaddr
> directly) are handled.

Closes: https://github.com/erofs/erofs-utils/issues/39

Also, a proper Signed-off-by: is needed.

> ---
>   include/erofs/blobchunk.h |  1 +
>   lib/blobchunk.c           | 40 +++++++++++++++++++++++++++++++++++----
>   lib/inode.c               |  3 +++
>   3 files changed, 40 insertions(+), 4 deletions(-)
> 
> diff --git a/include/erofs/blobchunk.h b/include/erofs/blobchunk.h
> index ef06773..48fca63 100644
> --- a/include/erofs/blobchunk.h
> +++ b/include/erofs/blobchunk.h
> @@ -16,6 +16,7 @@ extern "C"
>   
>   struct erofs_blobchunk *erofs_get_unhashed_chunk(unsigned int device_id,
>   		erofs_blk_t blkaddr, erofs_off_t sourceoffset);
> +void erofs_inode_fixup_chunkformat(struct erofs_inode *inode);
>   int erofs_write_chunk_indexes(struct erofs_inode *inode, struct erofs_vfile *vf,
>   			      erofs_off_t off);
>   int erofs_blob_write_chunked_file(struct erofs_inode *inode, int fd,
> diff --git a/lib/blobchunk.c b/lib/blobchunk.c
> index a051904..96c161b 100644
> --- a/lib/blobchunk.c
> +++ b/lib/blobchunk.c
> @@ -136,6 +136,42 @@ static int erofs_blob_hashmap_cmp(const void *a, const void *b,
>   		      sizeof(ec1->sha256));
>   }
>   

...


>   int erofs_write_chunk_indexes(struct erofs_inode *inode, struct erofs_vfile *vf,
>   			      erofs_off_t off)
>   {
> @@ -380,10 +416,6 @@ int erofs_blob_write_chunked_file(struct erofs_inode *inode, int fd,
>   			goto err;
>   		}
>   
> -		/* FIXME! `chunk->blkaddr` is not the final blkaddr here */
> -		if (chunk->blkaddr != EROFS_NULL_ADDR &&
> -		    chunk->blkaddr >= UINT32_MAX)
> -			inode->u.chunkformat |= EROFS_CHUNK_FORMAT_48BIT;
>   		if (!erofs_blob_can_merge(sbi, lastch, chunk)) {
>   			erofs_update_minextblks(sbi, interval_start, pos,
>   						&minextblks);
> diff --git a/lib/inode.c b/lib/inode.c
> index 4a214f9..7a1d982 100644
> --- a/lib/inode.c
> +++ b/lib/inode.c
> @@ -908,6 +908,9 @@ static int erofs_bh_flush_write_inode(struct erofs_buffer_head *bh, bool abort)
>   
>   	DBG_BUGON(inode->bh != bh);
>   	if (!abort) {
> +		if (inode->datalayout == EROFS_INODE_CHUNK_BASED &&
> +		    inode->chunkindexes)
> +			erofs_inode_fixup_chunkformat(inode);

How about moving this into erofs_iflush() rather than here?

Thanks,
Gao Xiang

>   		ret = erofs_iflush(inode);
>   		if (ret)
>   			return ret;