iomap: fix inline data on buffered read

Previously, iomap_readpage_iter() returning 0 would break out of the
loops of iomap_readahead_iter(), which is what iomap_read_inline_data()
relies on.

However, commit d9dc477 ("iomap: advance the iter directly on
buffered read") changes this behavior without calling
iomap_iter_advance(), which causes EROFS to get stuck in
iomap_readpage_iter().

It seems iomap_iter_advance() cannot be called in
iomap_read_inline_data() because of the iomap_write_begin() path, so
handle this in iomap_readpage_iter() instead.

Reported-and-tested-by: Bo Liu <[email protected]>
Fixes: d9dc477 ("iomap: advance the iter directly on buffered read")
Cc: Brian Foster <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: "Darrick J. Wong" <[email protected]>
Cc: Christian Brauner <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Brian Foster <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: hsiangkao

fs/iomap/buffered-io.c

@@ -372,9 +372,14 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
 	struct iomap_folio_state *ifs;
 	size_t poff, plen;
 	sector_t sector;
+	int ret;
 
-	if (iomap->type == IOMAP_INLINE)
-		return iomap_read_inline_data(iter, folio);
+	if (iomap->type == IOMAP_INLINE) {
+		ret = iomap_read_inline_data(iter, folio);
+		if (ret)
+			return ret;
+		return iomap_iter_advance(iter, &length);
+	}
 
 	/* zero post-eof blocks as the page may be mapped */
 	ifs = ifs_alloc(iter->inode, folio, iter->flags);