dm-crypt: enable DM_TARGET_ATOMIC_WRITES

Allow handling of bios with REQ_ATOMIC flag set.

Don't split these bios and fail them if they overrun the hard limit
"BIO_MAX_VECS << PAGE_SHIFT".

In order to simplify the code, this commit joins the logic that avoids
splitting emulated zone append bios with the logic that avoids
splitting atomic write bios.

Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Tested-by: John Garry <john.g.garry@oracle.com>

Author: Mikulas Patocka

drivers/md/dm-crypt.c

@@ -254,22 +254,15 @@ static unsigned int max_write_size = 0;
 module_param(max_write_size, uint, 0644);
 MODULE_PARM_DESC(max_write_size, "Maximum size of a write request");
 
-static unsigned get_max_request_sectors(struct dm_target *ti, struct bio *bio)
+static unsigned get_max_request_sectors(struct dm_target *ti, struct bio *bio, bool no_split)
 {
 	struct crypt_config *cc = ti->private;
 	unsigned val, sector_align;
 	bool wrt = op_is_write(bio_op(bio));
 
-	if (wrt) {
-		/*
-		 * For zoned devices, splitting write operations creates the
-		 * risk of deadlocking queue freeze operations with zone write
-		 * plugging BIO work when the reminder of a split BIO is
-		 * issued. So always allow the entire BIO to proceed.
-		 */
-		if (ti->emulate_zone_append)
-			return bio_sectors(bio);
-
+	if (no_split) {
+		val = -1;
+	} else if (wrt) {
 		val = min_not_zero(READ_ONCE(max_write_size),
 				   DM_CRYPT_DEFAULT_MAX_WRITE_SIZE);
 	} else {
@@ -3462,6 +3455,7 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
 	struct dm_crypt_io *io;
 	struct crypt_config *cc = ti->private;
 	unsigned max_sectors;
+	bool no_split;
 
 	/*
 	 * If bio is REQ_PREFLUSH or REQ_OP_DISCARD, just bypass crypt queues.
@@ -3479,10 +3473,20 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
 
 	/*
 	 * Check if bio is too large, split as needed.
+	 *
+	 * For zoned devices, splitting write operations creates the
+	 * risk of deadlocking queue freeze operations with zone write
+	 * plugging BIO work when the reminder of a split BIO is
+	 * issued. So always allow the entire BIO to proceed.
 	 */
-	max_sectors = get_max_request_sectors(ti, bio);
-	if (unlikely(bio_sectors(bio) > max_sectors))
+	no_split = (ti->emulate_zone_append && op_is_write(bio_op(bio))) ||
+		   (bio->bi_opf & REQ_ATOMIC);
+	max_sectors = get_max_request_sectors(ti, bio, no_split);
+	if (unlikely(bio_sectors(bio) > max_sectors)) {
+		if (unlikely(no_split))
+			return DM_MAPIO_KILL;
 		dm_accept_partial_bio(bio, max_sectors);
+	}
 
 	/*
 	 * Ensure that bio is a multiple of internal sector encryption size
@@ -3728,15 +3732,20 @@ static void crypt_io_hints(struct dm_target *ti, struct queue_limits *limits)
 	if (ti->emulate_zone_append)
 		limits->max_hw_sectors = min(limits->max_hw_sectors,
 					     BIO_MAX_VECS << PAGE_SECTORS_SHIFT);
+
+	limits->atomic_write_hw_unit_max = min(limits->atomic_write_hw_unit_max,
+					       BIO_MAX_VECS << PAGE_SHIFT);
+	limits->atomic_write_hw_max = min(limits->atomic_write_hw_max,
+					  BIO_MAX_VECS << PAGE_SHIFT);
 }
 
 static struct target_type crypt_target = {
 	.name   = "crypt",
-	.version = {1, 28, 0},
+	.version = {1, 29, 0},
 	.module = THIS_MODULE,
 	.ctr    = crypt_ctr,
 	.dtr    = crypt_dtr,
-	.features = DM_TARGET_ZONED_HM,
+	.features = DM_TARGET_ZONED_HM | DM_TARGET_ATOMIC_WRITES,
 	.report_zones = crypt_report_zones,
 	.map    = crypt_map,
 	.status = crypt_status,