[PATCH] Enable loading of bitmaps for dm-md-raid1.

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

This is also a hack for systems with junk in the rest
of the bitmap super (instead of zeroes) to boot. This is done by
checking mddev->sync_super (which is exclusively set by dm-raid)
is null.

These changes also include zeroing of most bitmap pages while
allocating so we are sure that the junk is not coming from memory.

References: https://bugzilla.kernel.org/show_bug.cgi?id=100491

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 135a090..dfa5ef3 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -494,7 +494,7 @@ static int bitmap_new_disk_sb(struct bitmap *bitmap)
 	bitmap_super_t *sb;
 	unsigned long chunksize, daemon_sleep, write_behind;
 
-	bitmap->storage.sb_page = alloc_page(GFP_KERNEL);
+	bitmap->storage.sb_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (bitmap->storage.sb_page == NULL)
 		return -ENOMEM;
 	bitmap->storage.sb_page->index = 0;
@@ -541,6 +541,7 @@ static int bitmap_new_disk_sb(struct bitmap *bitmap)
 	sb->state = cpu_to_le32(bitmap->flags);
 	bitmap->events_cleared = bitmap->mddev->events;
 	sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
+	bitmap->mddev->bitmap_info.nodes = 0;
 
 	kunmap_atomic(sb);
 
@@ -568,7 +569,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
 		goto out_no_sb;
 	}
 	/* page 0 is the superblock, read it... */
-	sb_page = alloc_page(GFP_KERNEL);
+	sb_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (!sb_page)
 		return -ENOMEM;
 	bitmap->storage.sb_page = sb_page;
@@ -611,8 +612,15 @@ re_read:
 	daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
 	write_behind = le32_to_cpu(sb->write_behind);
 	sectors_reserved = le32_to_cpu(sb->sectors_reserved);
-	nodes = le32_to_cpu(sb->nodes);
-	strlcpy(bitmap->mddev->bitmap_info.cluster_name, sb->cluster_name, 64);
+	/* XXX: This is an ugly hack to ensure that we don't use clustering
+	   in case dm-raid is in use and the nodes written in bitmap_sb
+	   is erroneous.
+	*/
+	if (!bitmap->mddev->sync_super) {
+		nodes = le32_to_cpu(sb->nodes);
+		strlcpy(bitmap->mddev->bitmap_info.cluster_name,
+				sb->cluster_name, 64);
+	}
 
 	/* verify that the bitmap-specific fields are valid */
 	if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
@@ -649,7 +657,7 @@ re_read:
 			goto out;
 		}
 		events = le64_to_cpu(sb->events);
-		if (!nodes && (events < bitmap->mddev->events)) {
+		if (err == 0 && !nodes && (events < bitmap->mddev->events)) {
 			printk(KERN_INFO
 			       "%s: bitmap file is out of date (%llu < %llu) "
 			       "-- forcing full recovery\n",
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4dbed4a..6bd8bc3 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7415,7 +7415,7 @@ int md_setup_cluster(struct mddev *mddev, int nodes)
 	err = request_module("md-cluster");
 	if (err) {
 		pr_err("md-cluster module not found.\n");
-		return err;
+		return -ENOENT;
 	}
 
 	spin_lock(&pers_lock);