From 70266e0c1432f33754bd807f0e104f1541888403 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@redhat.com>
Date: Wed, 30 Mar 2011 21:55:51 -0400
Subject: [PATCH 1/5] initial refactor of DM integrity support

---
 drivers/md/dm-table.c |  102 +++++++++++++++++++++++++++++++-----------------
 1 files changed, 66 insertions(+), 36 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 416d4e2..f3f70d6 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -927,19 +927,72 @@ static int dm_table_build_index(struct dm_table *t)
 }
 
 /*
+ * Get the integrity profile for the table.
+ * If %compare is true, all devices' profiles must match.
+ * If %compare is false, all devices must at least have an
+ * allocated integrity profile.
+ * FIXME: add a new integrity method: blk_integrity_initialized() to
+ * skip comparisons with uninitialized profiles during table load.
+ */
+static struct blk_integrity *dm_table_get_integrity(struct dm_table *t, bool compare)
+{
+	struct list_head *devices = dm_table_get_devices(t);
+	struct dm_dev_internal *prev = NULL, *dd = NULL;
+
+	list_for_each_entry(dd, devices, list) {
+		if (compare && prev &&
+		    blk_integrity_compare(prev->dm_dev.bdev->bd_disk,
+					  dd->dm_dev.bdev->bd_disk) < 0) {
+			DMWARN("%s: integrity not set: %s and %s mismatch",
+			       dm_device_name(t->md),
+			       prev->dm_dev.bdev->bd_disk->disk_name,
+			       dd->dm_dev.bdev->bd_disk->disk_name);
+			goto no_integrity;
+		} else if (!bdev_get_integrity(dd->dm_dev.bdev))
+			goto no_integrity;
+		prev = dd;
+	}
+
+	if (prev)
+		return bdev_get_integrity(prev->dm_dev.bdev);
+
+no_integrity:
+	return NULL;
+}
+
+/*
  * Register the mapped device for blk_integrity support if
- * the underlying devices support it.
+ * the underlying devices have an integrity profile.  But all devices
+ * may not have matching profiles (checking all devices isn't reliable
+ * during table load because this table may use other DM device(s) which
+ * must be resumed before they will have an initialized integity profile).
+ * Stacked DM devices force a 2 stage integrity profile validation:
+ * 1 - during load, validate all initialized integrity profiles match
+ * 2 - during resume, validate all integrity profiles match
  */
 static int dm_table_prealloc_integrity(struct dm_table *t, struct mapped_device *md)
 {
-	struct list_head *devices = dm_table_get_devices(t);
-	struct dm_dev_internal *dd;
+	struct blk_integrity *bi = NULL;
 
-	list_for_each_entry(dd, devices, list)
-		if (bdev_get_integrity(dd->dm_dev.bdev)) {
-			t->integrity_supported = 1;
-			return blk_integrity_register(dm_disk(md), NULL);
-		}
+	bi = dm_table_get_integrity(t, false);
+	if (bi) {
+		/*
+		 * FIXME: if device already has an initalized integrity
+		 * profile the new table's profile should not conflict.
+		 * - return 'struct gendisk' from dm_table_get_integrity?
+		 * - feed gendisk to existing blk_integrity_compare()?
+		 */
+
+		t->integrity_supported = 1;
+
+		/*
+		 * Avoid clearing a previously established integrity profile
+		 */
+		if (bdev_get_integrity(dm_disk(md)))
+			return 0;
+
+		return blk_integrity_register(dm_disk(md), NULL);
+	}
 
 	return 0;
 }
@@ -1094,41 +1147,18 @@ combine_limits:
 
 /*
  * Set the integrity profile for this device if all devices used have
- * matching profiles.
+ * matching profiles.  We're quite deep in the resume path but still
+ * don't know if all devices have matching profiles.
+ * FIXME: even if they didn't match we have no existing way to fail
+ * to resume at this point.
  */
 static void dm_table_set_integrity(struct dm_table *t)
 {
-	struct list_head *devices = dm_table_get_devices(t);
-	struct dm_dev_internal *prev = NULL, *dd = NULL;
-
 	if (!blk_get_integrity(dm_disk(t->md)))
 		return;
 
-	list_for_each_entry(dd, devices, list) {
-		if (prev &&
-		    blk_integrity_compare(prev->dm_dev.bdev->bd_disk,
-					  dd->dm_dev.bdev->bd_disk) < 0) {
-			DMWARN("%s: integrity not set: %s and %s mismatch",
-			       dm_device_name(t->md),
-			       prev->dm_dev.bdev->bd_disk->disk_name,
-			       dd->dm_dev.bdev->bd_disk->disk_name);
-			goto no_integrity;
-		}
-		prev = dd;
-	}
-
-	if (!prev || !bdev_get_integrity(prev->dm_dev.bdev))
-		goto no_integrity;
-
 	blk_integrity_register(dm_disk(t->md),
-			       bdev_get_integrity(prev->dm_dev.bdev));
-
-	return;
-
-no_integrity:
-	blk_integrity_register(dm_disk(t->md), NULL);
-
-	return;
+			       dm_table_get_integrity(t, true));
 }
 
 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
-- 
1.7.3.4