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

[puneeth_aditya_5656 <myakampuneeth@gmail.com>]

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.
---
 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));
 }
 
+void erofs_inode_fixup_chunkformat(struct erofs_inode *inode)
+{
+	unsigned int unit, src;
+	u64 extent_count;
+	bool _48bit;
+
+	if (inode->u.chunkformat & EROFS_CHUNK_FORMAT_INDEXES)
+		unit = sizeof(struct erofs_inode_chunk_index);
+	else
+		unit = EROFS_BLOCK_MAP_ENTRY_SIZE;
+
+	_48bit = inode->u.chunkformat & EROFS_CHUNK_FORMAT_48BIT;
+	if (_48bit)
+		return;
+
+	extent_count = inode->extent_isize / unit;
+	for (src = 0; src < extent_count; ++src) {
+		struct erofs_blobchunk *chunk =
+			*(void **)(inode->chunkindexes + src * sizeof(void *));
+
+		if (chunk->blkaddr == EROFS_NULL_ADDR)
+			continue;
+		if (chunk->device_id) {
+			if (chunk->blkaddr > UINT32_MAX) {
+				_48bit = true;
+				break;
+			}
+		} else if (remapped_base + chunk->blkaddr > UINT32_MAX) {
+			_48bit = true;
+			break;
+		}
+	}
+	if (_48bit)
+		inode->u.chunkformat |= EROFS_CHUNK_FORMAT_48BIT;
+}
+
 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);
 		ret = erofs_iflush(inode);
 		if (ret)
 			return ret;
-- 
2.52.0