Btrfs: RAID5 and RAID6

This builds on David Woodhouse's original Btrfs raid5/6 implementation.
The code has changed quite a bit, blame Chris Mason for any bugs.

Read/modify/write is done after the higher levels of the filesystem have
prepared a given bio.  This means the higher layers are not responsible
for building full stripes, and they don't need to query for the topology
of the extents that may get allocated during delayed allocation runs.
It also means different files can easily share the same stripe.

But, it does expose us to incorrect parity if we crash or lose power
while doing a read/modify/write cycle.  This will be addressed in a
later commit.

Scrub is unable to repair crc errors on raid5/6 chunks.

Discard does not work on raid5/6 (yet)

The stripe size is fixed at 64KiB per disk.  This will be tunable
in a later commit.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
new file mode 100644
index 0000000..ea5d73b
--- /dev/null
+++ b/fs/btrfs/raid56.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2012 Fusion-io  All rights reserved.
+ * Copyright (C) 2012 Intel Corp. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#ifndef __BTRFS_RAID56__
+#define __BTRFS_RAID56__
+static inline int nr_parity_stripes(struct map_lookup *map)
+{
+	if (map->type & BTRFS_BLOCK_GROUP_RAID5)
+		return 1;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+		return 2;
+	else
+		return 0;
+}
+
+static inline int nr_data_stripes(struct map_lookup *map)
+{
+	return map->num_stripes - nr_parity_stripes(map);
+}
+#define RAID5_P_STRIPE ((u64)-2)
+#define RAID6_Q_STRIPE ((u64)-1)
+
+#define is_parity_stripe(x) (((x) == RAID5_P_STRIPE) ||		\
+			     ((x) == RAID6_Q_STRIPE))
+
+int raid56_parity_recover(struct btrfs_root *root, struct bio *bio,
+				 struct btrfs_bio *bbio, u64 *raid_map,
+				 u64 stripe_len, int mirror_num);
+int raid56_parity_write(struct btrfs_root *root, struct bio *bio,
+			       struct btrfs_bio *bbio, u64 *raid_map,
+			       u64 stripe_len);
+
+int btrfs_alloc_stripe_hash_table(struct btrfs_fs_info *info);
+void btrfs_free_stripe_hash_table(struct btrfs_fs_info *info);
+#endif