filemap: fix page_cache_next_miss() when no hole found

page_cache_next_miss() should return value outside of the specified range
when no hole is found.  However currently it will return the last index
*in* the specified range confusing ondemand_readahead() to think there's a
hole in the searched range and upsetting readahead logic.

Link: https://lkml.kernel.org/r/20240625101909.12234-2-jack@suse.cz


Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: Zhang Peng <zhangpengpeng0808@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>