ext4: init pagevec in ext4_da_block_invalidatepages

commit 66bea92c 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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/ext4/inode.c

@@ -1422,6 +1422,7 @@ 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)