ext4: init pagevec in ext4_da_block_invalidatepages

Orabug: 17488415

commit 66bea92 upstream.

ext4_da_block_invalidatepages is missing a pagevec_init(),
which means that pvec->cold contains random garbage.

This affects whether the page goes to the front or
back of the LRU when ->cold makes it to
free_hot_cold_page()

Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit 97765f30c49d3023a6dafe7c48c7e520fca441f8)

Signed-off-by: Todd Vierling <todd.vierling@oracle.com>
Acked-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

Author: Eric Sandeen

fs/ext4/inode.c

@@ -2206,6 +2206,8 @@ static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd)
 
 	index = mpd->first_page;
 	end   = mpd->next_page - 1;
+
+	pagevec_init(&pvec, 0);
 	while (index <= end) {
 		nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
 		if (nr_pages == 0)