dm integrity: reduce vmalloc space footprint on 32-bit architectures

It was reported that dm-integrity runs out of vmalloc space on 32-bit
architectures. On x86, there is only 128MiB vmalloc space and dm-integrity
consumes it quickly because it has a 64MiB journal and 8MiB recalculate
buffer.

Fix this by reducing the size of the journal to 4MiB and the size of
the recalculate buffer to 1MiB, so that multiple dm-integrity devices
can be created and activated on 32-bit architectures.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Author: Mikulas Patocka

drivers/md/dm-integrity.c

@@ -34,11 +34,11 @@
 #define DEFAULT_BUFFER_SECTORS		128
 #define DEFAULT_JOURNAL_WATERMARK	50
 #define DEFAULT_SYNC_MSEC		10000
-#define DEFAULT_MAX_JOURNAL_SECTORS	131072
+#define DEFAULT_MAX_JOURNAL_SECTORS	(IS_ENABLED(CONFIG_64BIT) ? 131072 : 8192)
 #define MIN_LOG2_INTERLEAVE_SECTORS	3
 #define MAX_LOG2_INTERLEAVE_SECTORS	31
 #define METADATA_WORKQUEUE_MAX_ACTIVE	16
-#define RECALC_SECTORS			32768
+#define RECALC_SECTORS			(IS_ENABLED(CONFIG_64BIT) ? 32768 : 2048)
 #define RECALC_WRITE_SUPER		16
 #define BITMAP_BLOCK_SIZE		4096	/* don't change it */
 #define BITMAP_FLUSH_INTERVAL		(10 * HZ)