On 2026/2/25 03:13, 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

I think the first case is impossible for the current remapping
mechanism.

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_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.

Signed-off-by: Puneeth Aditya <[email protected]>
---
  include/erofs/blobchunk.h |  1 +
  lib/blobchunk.c           | 40 +++++++++++++++++++++++++++++++++++----
  lib/inode.c               |  2 ++
  3 files changed, 39 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..25087ca 100644
--- a/lib/inode.c
+++ b/lib/inode.c
@@ -794,6 +794,8 @@ int erofs_iflush(struct erofs_inode *inode)
        } else if (is_inode_layout_compression(inode)) {
                u1.blocks_lo = cpu_to_le32(inode->u.i_blocks);
        } else if (inode->datalayout == EROFS_INODE_CHUNK_BASED) {
+               if (inode->chunkindexes)

It's a useless check, just remove this.

Thanks,
Gao Xiang

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