Btrfs: add basic infrastructure for selective balancing

This allows to have a separate set of filters for each chunk type
(data,meta,sys).  The code however is generic and switch on chunk type
is only done once.

This commit also adds a type filter: it allows to balance for example
meta and system chunks w/o touching data ones.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 57 insertions, 2 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 9fc06e6bc51a..91bbf6e774c0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2102,6 +2102,30 @@ static void unset_balance_control(struct btrfs_fs_info *fs_info)
         kfree(bctl);
 }
 
+static int should_balance_chunk(struct btrfs_root *root,
+                                struct extent_buffer *leaf,
+                                struct btrfs_chunk *chunk, u64 chunk_offset)
+{
+        struct btrfs_balance_control *bctl = root->fs_info->balance_ctl;
+        struct btrfs_balance_args *bargs = NULL;
+        u64 chunk_type = btrfs_chunk_type(leaf, chunk);
+
+        /* type filter */
+        if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) &
+              (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) {
+                return 0;
+        }
+
+        if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
+                bargs = &bctl->data;
+        else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
+                bargs = &bctl->sys;
+        else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
+                bargs = &bctl->meta;
+
+        return 1;
+}
+
 static u64 div_factor(u64 num, int factor)
 {
         if (factor == 10)
@@ -2119,10 +2143,13 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
         struct btrfs_device *device;
         u64 old_size;
         u64 size_to_free;
+        struct btrfs_chunk *chunk;
         struct btrfs_path *path;
         struct btrfs_key key;
         struct btrfs_key found_key;
         struct btrfs_trans_handle *trans;
+        struct extent_buffer *leaf;
+        int slot;
         int ret;
         int enospc_errors = 0;
 
@@ -2179,8 +2206,10 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
                         break;
                 }
 
-                btrfs_item_key_to_cpu(path->nodes[0], &found_key,
-                                      path->slots[0]);
+                leaf = path->nodes[0];
+                slot = path->slots[0];
+                btrfs_item_key_to_cpu(leaf, &found_key, slot);
+
                 if (found_key.objectid != key.objectid)
                         break;
 
@@ -2188,7 +2217,14 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
                 if (found_key.offset == 0)
                         break;
 
+                chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
+
+                ret = should_balance_chunk(chunk_root, leaf, chunk,
+                                           found_key.offset);
                 btrfs_release_path(path);
+                if (!ret)
+                        goto loop;
+
                 ret = btrfs_relocate_chunk(chunk_root,
                                            chunk_root->root_key.objectid,
                                            found_key.objectid,
@@ -2197,6 +2233,7 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
                         goto error;
                 if (ret == -ENOSPC)
                         enospc_errors++;
+loop:
                 key.offset = found_key.offset - 1;
         }
 
@@ -2227,6 +2264,7 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
                   struct btrfs_ioctl_balance_args *bargs)
 {
         struct btrfs_fs_info *fs_info = bctl->fs_info;
+        u64 allowed;
         int ret;
 
         if (btrfs_fs_closing(fs_info)) {
@@ -2234,6 +2272,23 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
                 goto out;
         }
 
+        /*
+         * In case of mixed groups both data and meta should be picked,
+         * and identical options should be given for both of them.
+         */
+        allowed = btrfs_super_incompat_flags(fs_info->super_copy);
+        if ((allowed & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
+            (bctl->flags & (BTRFS_BALANCE_DATA | BTRFS_BALANCE_METADATA))) {
+                if (!(bctl->flags & BTRFS_BALANCE_DATA) ||
+                    !(bctl->flags & BTRFS_BALANCE_METADATA) ||
+                    memcmp(&bctl->data, &bctl->meta, sizeof(bctl->data))) {
+                        printk(KERN_ERR "btrfs: with mixed groups data and "
+                               "metadata balance options must be the same\n");
+                        ret = -EINVAL;
+                        goto out;
+                }
+        }
+
         set_balance_control(bctl);
 
         mutex_unlock(&fs_info->balance_mutex);