Btrfs: implement online profile changing

Profile changing is done by launching a balance with
BTRFS_BALANCE_CONVERT bits set and target fields of respective
btrfs_balance_args structs initialized.  Profile reducing code in this
case will pick restriper's target profile if it's available instead of
doing a blind reduce.  If target profile is not yet available it goes
back to a plain reduce.

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

1 files changed, 69 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e86c9e4fe51e..f08210e83339 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2438,6 +2438,75 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
                 }
         }
 
+        /*
+         * Profile changing sanity checks.  Skip them if a simple
+         * balance is requested.
+         */
+        if (!((bctl->data.flags | bctl->sys.flags | bctl->meta.flags) &
+              BTRFS_BALANCE_ARGS_CONVERT))
+                goto do_balance;
+
+        allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
+        if (fs_info->fs_devices->num_devices == 1)
+                allowed |= BTRFS_BLOCK_GROUP_DUP;
+        else if (fs_info->fs_devices->num_devices < 4)
+                allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
+        else
+                allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
+                                BTRFS_BLOCK_GROUP_RAID10);
+
+        if (!profile_is_valid(bctl->data.target, 1) ||
+            bctl->data.target & ~allowed) {
+                printk(KERN_ERR "btrfs: unable to start balance with target "
+                       "data profile %llu\n",
+                       (unsigned long long)bctl->data.target);
+                ret = -EINVAL;
+                goto out;
+        }
+        if (!profile_is_valid(bctl->meta.target, 1) ||
+            bctl->meta.target & ~allowed) {
+                printk(KERN_ERR "btrfs: unable to start balance with target "
+                       "metadata profile %llu\n",
+                       (unsigned long long)bctl->meta.target);
+                ret = -EINVAL;
+                goto out;
+        }
+        if (!profile_is_valid(bctl->sys.target, 1) ||
+            bctl->sys.target & ~allowed) {
+                printk(KERN_ERR "btrfs: unable to start balance with target "
+                       "system profile %llu\n",
+                       (unsigned long long)bctl->sys.target);
+                ret = -EINVAL;
+                goto out;
+        }
+
+        if (bctl->data.target & BTRFS_BLOCK_GROUP_DUP) {
+                printk(KERN_ERR "btrfs: dup for data is not allowed\n");
+                ret = -EINVAL;
+                goto out;
+        }
+
+        /* allow to reduce meta or sys integrity only if force set */
+        allowed = BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
+                        BTRFS_BLOCK_GROUP_RAID10;
+        if (((bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
+             (fs_info->avail_system_alloc_bits & allowed) &&
+             !(bctl->sys.target & allowed)) ||
+            ((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
+             (fs_info->avail_metadata_alloc_bits & allowed) &&
+             !(bctl->meta.target & allowed))) {
+                if (bctl->flags & BTRFS_BALANCE_FORCE) {
+                        printk(KERN_INFO "btrfs: force reducing metadata "
+                               "integrity\n");
+                } else {
+                        printk(KERN_ERR "btrfs: balance will reduce metadata "
+                               "integrity, use force if you want this\n");
+                        ret = -EINVAL;
+                        goto out;
+                }
+        }
+
+do_balance:
         set_balance_control(bctl);
 
         mutex_unlock(&fs_info->balance_mutex);