ext4 crypto: fix some error handling

BugLink: http://bugs.launchpad.net/bugs/1694621

commit 4762cc3f upstream.

We should be testing for -ENOMEM but the minus sign is missing.

Fixes: c9af28fd ('ext4 crypto: don't let data integrity writebacks fail with ENOMEM')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

fs/ext4/page-io.c

@@ -492,7 +492,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
 		data_page = ext4_encrypt(inode, page, gfp_flags);
 		if (IS_ERR(data_page)) {
 			ret = PTR_ERR(data_page);
-			if (ret == ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
+			if (ret == -ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
 				if (io->io_bio) {
 					ext4_io_submit(io);
 					congestion_wait(BLK_RW_ASYNC, HZ/50);