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, 59 insertions, 29 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d133edfcd449..3345f68fc64b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -31,6 +31,7 @@
 #include "print-tree.h"
 #include "transaction.h"
 #include "volumes.h"
+#include "raid56.h"
 #include "locking.h"
 #include "free-space-cache.h"
 #include "math.h"
@@ -1852,6 +1853,8 @@ static int btrfs_discard_extent(struct btrfs_root *root, u64 bytenr,
                 *actual_bytes = discarded_bytes;
 
 
+        if (ret == -EOPNOTSUPP)
+                ret = 0;
         return ret;
 }
 
@@ -3276,6 +3279,7 @@ u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags)
         u64 num_devices = root->fs_info->fs_devices->rw_devices +
                 root->fs_info->fs_devices->missing_devices;
         u64 target;
+        u64 tmp;
 
         /*
          * see if restripe for this chunk_type is in progress, if so
@@ -3292,30 +3296,32 @@ u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags)
         }
         spin_unlock(&root->fs_info->balance_lock);
 
+        /* First, mask out the RAID levels which aren't possible */
         if (num_devices == 1)
-                flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0);
+                flags &= ~(BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID0 |
+                           BTRFS_BLOCK_GROUP_RAID5);
+        if (num_devices < 3)
+                flags &= ~BTRFS_BLOCK_GROUP_RAID6;
         if (num_devices < 4)
                 flags &= ~BTRFS_BLOCK_GROUP_RAID10;
 
-        if ((flags & BTRFS_BLOCK_GROUP_DUP) &&
-            (flags & (BTRFS_BLOCK_GROUP_RAID1 |
-                      BTRFS_BLOCK_GROUP_RAID10))) {
-                flags &= ~BTRFS_BLOCK_GROUP_DUP;
-        }
-
-        if ((flags & BTRFS_BLOCK_GROUP_RAID1) &&
-            (flags & BTRFS_BLOCK_GROUP_RAID10)) {
-                flags &= ~BTRFS_BLOCK_GROUP_RAID1;
-        }
+        tmp = flags & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID0 |
+                       BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID5 |
+                       BTRFS_BLOCK_GROUP_RAID6 | BTRFS_BLOCK_GROUP_RAID10);
+        flags &= ~tmp;
 
-        if ((flags & BTRFS_BLOCK_GROUP_RAID0) &&
-            ((flags & BTRFS_BLOCK_GROUP_RAID1) |
-             (flags & BTRFS_BLOCK_GROUP_RAID10) |
-             (flags & BTRFS_BLOCK_GROUP_DUP))) {
-                flags &= ~BTRFS_BLOCK_GROUP_RAID0;
-        }
+        if (tmp & BTRFS_BLOCK_GROUP_RAID6)
+                tmp = BTRFS_BLOCK_GROUP_RAID6;
+        else if (tmp & BTRFS_BLOCK_GROUP_RAID5)
+                tmp = BTRFS_BLOCK_GROUP_RAID5;
+        else if (tmp & BTRFS_BLOCK_GROUP_RAID10)
+                tmp = BTRFS_BLOCK_GROUP_RAID10;
+        else if (tmp & BTRFS_BLOCK_GROUP_RAID1)
+                tmp = BTRFS_BLOCK_GROUP_RAID1;
+        else if (tmp & BTRFS_BLOCK_GROUP_RAID0)
+                tmp = BTRFS_BLOCK_GROUP_RAID0;
 
-        return extended_to_chunk(flags);
+        return extended_to_chunk(flags | tmp);
 }
 
 static u64 get_alloc_profile(struct btrfs_root *root, u64 flags)
@@ -3333,6 +3339,7 @@ static u64 get_alloc_profile(struct btrfs_root *root, u64 flags)
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data)
 {
         u64 flags;
+        u64 ret;
 
         if (data)
                 flags = BTRFS_BLOCK_GROUP_DATA;
@@ -3341,7 +3348,8 @@ u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data)
         else
                 flags = BTRFS_BLOCK_GROUP_METADATA;
 
-        return get_alloc_profile(root, flags);
+        ret = get_alloc_profile(root, flags);
+        return ret;
 }
 
 /*
@@ -3516,8 +3524,10 @@ static u64 get_system_chunk_thresh(struct btrfs_root *root, u64 type)
 {
         u64 num_dev;
 
-        if (type & BTRFS_BLOCK_GROUP_RAID10 ||
-            type & BTRFS_BLOCK_GROUP_RAID0)
+        if (type & (BTRFS_BLOCK_GROUP_RAID10 |
+                    BTRFS_BLOCK_GROUP_RAID0 |
+                    BTRFS_BLOCK_GROUP_RAID5 |
+                    BTRFS_BLOCK_GROUP_RAID6))
                 num_dev = root->fs_info->fs_devices->rw_devices;
         else if (type & BTRFS_BLOCK_GROUP_RAID1)
                 num_dev = 2;
@@ -3667,7 +3677,9 @@ static int can_overcommit(struct btrfs_root *root,
 
         /*
          * If we have dup, raid1 or raid10 then only half of the free
-         * space is actually useable.
+         * space is actually useable.  For raid56, the space info used
+         * doesn't include the parity drive, so we don't have to
+         * change the math
          */
         if (profile & (BTRFS_BLOCK_GROUP_DUP |
                        BTRFS_BLOCK_GROUP_RAID1 |
@@ -5455,10 +5467,14 @@ int btrfs_free_extent(struct btrfs_trans_handle *trans, struct btrfs_root *root,
         return ret;
 }
 
-static u64 stripe_align(struct btrfs_root *root, u64 val)
+static u64 stripe_align(struct btrfs_root *root,
+                        struct btrfs_block_group_cache *cache,
+                        u64 val, u64 num_bytes)
 {
-        u64 mask = ((u64)root->stripesize - 1);
-        u64 ret = (val + mask) & ~mask;
+        u64 mask;
+        u64 ret;
+        mask = ((u64)root->stripesize - 1);
+        ret = (val + mask) & ~mask;
         return ret;
 }
 
@@ -5519,9 +5535,12 @@ int __get_raid_index(u64 flags)
                 index = 2;
         else if (flags & BTRFS_BLOCK_GROUP_RAID0)
                 index = 3;
+        else if (flags & BTRFS_BLOCK_GROUP_RAID5)
+                index = 5;
+        else if (flags & BTRFS_BLOCK_GROUP_RAID6)
+                index = 6;
         else
-                index = 4;
-
+                index = 4; /* BTRFS_BLOCK_GROUP_SINGLE */
         return index;
 }
 
@@ -5665,6 +5684,8 @@ search:
                 if (!block_group_bits(block_group, data)) {
                     u64 extra = BTRFS_BLOCK_GROUP_DUP |
                                 BTRFS_BLOCK_GROUP_RAID1 |
+                                BTRFS_BLOCK_GROUP_RAID5 |
+                                BTRFS_BLOCK_GROUP_RAID6 |
                                 BTRFS_BLOCK_GROUP_RAID10;
 
                         /*
@@ -5835,7 +5856,8 @@ unclustered_alloc:
                         goto loop;
                 }
 checks:
-                search_start = stripe_align(root, offset);
+                search_start = stripe_align(root, used_block_group,
+                                            offset, num_bytes);
 
                 /* move on to the next group */
                 if (search_start + num_bytes >
@@ -7203,6 +7225,7 @@ static u64 update_block_group_flags(struct btrfs_root *root, u64 flags)
                 root->fs_info->fs_devices->missing_devices;
 
         stripped = BTRFS_BLOCK_GROUP_RAID0 |
+                BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6 |
                 BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10;
 
         if (num_devices == 1) {
@@ -7754,7 +7777,9 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                 btrfs_release_path(path);
                 cache->flags = btrfs_block_group_flags(&cache->item);
                 cache->sectorsize = root->sectorsize;
-
+                cache->full_stripe_len = btrfs_full_stripe_len(root,
+                                               &root->fs_info->mapping_tree,
+                                               found_key.objectid);
                 btrfs_init_free_space_ctl(cache);
 
                 /*
@@ -7808,6 +7833,8 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                 if (!(get_alloc_profile(root, space_info->flags) &
                       (BTRFS_BLOCK_GROUP_RAID10 |
                        BTRFS_BLOCK_GROUP_RAID1 |
+                       BTRFS_BLOCK_GROUP_RAID5 |
+                       BTRFS_BLOCK_GROUP_RAID6 |
                        BTRFS_BLOCK_GROUP_DUP)))
                         continue;
                 /*
@@ -7883,6 +7910,9 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
         cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
         cache->sectorsize = root->sectorsize;
         cache->fs_info = root->fs_info;
+        cache->full_stripe_len = btrfs_full_stripe_len(root,
+                                               &root->fs_info->mapping_tree,
+                                               chunk_offset);
 
         atomic_set(&cache->count, 1);
         spin_lock_init(&cache->lock);