iomap: fix inline data on buffered read

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 d9dc477ff6a2 ("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 <liubo03@inspur.com>
Fixes: d9dc477ff6a2 ("iomap: advance the iter directly on buffered read")
Cc: Brian Foster <bfoster@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250319085125.4039368-1-hsiangkao@linux.alibaba.com
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>