mm/filemap: change filemap_read_page calling conventions

Make this function more generic by passing the file instead of the iocb.
Check in the callers whether we should call readpage or not.  Also make it
return an errno / 0 / AOP_TRUNCATED_PAGE, and make calling put_page() the
caller's responsibility.

Link: https://lkml.kernel.org/r/20210122160140.223228-10-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>