Btrfs: allow for canceling restriper

Implement an ioctl for canceling restriper.  Currently we wait until
relocation of the current block group is finished, in future this can be
done by triggering a commit.  Balance item is deleted and no memory
about the interrupted balance is kept.

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

6 files changed, 53 insertions, 3 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1afda75d5414..dfc136cc07d7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1216,6 +1216,7 @@ struct btrfs_fs_info {
         struct mutex balance_mutex;
         atomic_t balance_running;
         atomic_t balance_pause_req;
+        atomic_t balance_cancel_req;
         struct btrfs_balance_control *balance_ctl;
         wait_queue_head_t balance_wait_q;
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8ce837407800..c23b82d8ec08 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2006,6 +2006,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         mutex_init(&fs_info->balance_mutex);
         atomic_set(&fs_info->balance_running, 0);
         atomic_set(&fs_info->balance_pause_req, 0);
+        atomic_set(&fs_info->balance_cancel_req, 0);
         fs_info->balance_ctl = NULL;
         init_waitqueue_head(&fs_info->balance_wait_q);
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f572c53dda4f..60852217ce9a 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3076,6 +3076,8 @@ void update_ioctl_balance_args(struct btrfs_fs_info *fs_info,
                 bargs->state |= BTRFS_BALANCE_STATE_RUNNING;
         if (atomic_read(&fs_info->balance_pause_req))
                 bargs->state |= BTRFS_BALANCE_STATE_PAUSE_REQ;
+        if (atomic_read(&fs_info->balance_cancel_req))
+                bargs->state |= BTRFS_BALANCE_STATE_CANCEL_REQ;
 
         memcpy(&bargs->data, &bctl->data, sizeof(bargs->data));
         memcpy(&bargs->meta, &bctl->meta, sizeof(bargs->meta));
@@ -3157,6 +3159,8 @@ static long btrfs_ioctl_balance_ctl(struct btrfs_root *root, int cmd)
         switch (cmd) {
         case BTRFS_BALANCE_CTL_PAUSE:
                 return btrfs_pause_balance(root->fs_info);
+        case BTRFS_BALANCE_CTL_CANCEL:
+                return btrfs_cancel_balance(root->fs_info);
         }
 
         return -EINVAL;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index e972e11a8d77..cd19d10794b9 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -111,6 +111,7 @@ struct btrfs_ioctl_fs_info_args {
 
 /* balance control ioctl modes */
 #define BTRFS_BALANCE_CTL_PAUSE         1
+#define BTRFS_BALANCE_CTL_CANCEL        2
 
 /*
  * this is packed, because it should be exactly the same as its disk
@@ -142,6 +143,7 @@ struct btrfs_balance_progress {
 
 #define BTRFS_BALANCE_STATE_RUNNING     (1ULL << 0)
 #define BTRFS_BALANCE_STATE_PAUSE_REQ   (1ULL << 1)
+#define BTRFS_BALANCE_STATE_CANCEL_REQ  (1ULL << 2)
 
 struct btrfs_ioctl_balance_args {
         __u64 flags;                            /* in/out */
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d32660ce753d..c32667318ae4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2492,7 +2492,8 @@ static int __btrfs_balance(struct btrfs_fs_info *fs_info)
         key.type = BTRFS_CHUNK_ITEM_KEY;
 
         while (1) {
-                if (atomic_read(&fs_info->balance_pause_req)) {
+                if (atomic_read(&fs_info->balance_pause_req) ||
+                    atomic_read(&fs_info->balance_cancel_req)) {
                         ret = -ECANCELED;
                         goto error;
                 }
@@ -2560,7 +2561,10 @@ error:
 
 static inline int balance_need_close(struct btrfs_fs_info *fs_info)
 {
-        return atomic_read(&fs_info->balance_pause_req) == 0;
+        /* cancel requested || normal exit path */
+        return atomic_read(&fs_info->balance_cancel_req) ||
+                (atomic_read(&fs_info->balance_pause_req) == 0 &&
+                 atomic_read(&fs_info->balance_cancel_req) == 0);
 }
 
 static void __cancel_balance(struct btrfs_fs_info *fs_info)
@@ -2586,7 +2590,8 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
         int ret;
 
         if (btrfs_fs_closing(fs_info) ||
-            atomic_read(&fs_info->balance_pause_req)) {
+            atomic_read(&fs_info->balance_pause_req) ||
+            atomic_read(&fs_info->balance_cancel_req)) {
                 ret = -EINVAL;
                 goto out;
         }
@@ -2832,6 +2837,42 @@ int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
         return ret;
 }
 
+int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
+{
+        mutex_lock(&fs_info->balance_mutex);
+        if (!fs_info->balance_ctl) {
+                mutex_unlock(&fs_info->balance_mutex);
+                return -ENOTCONN;
+        }
+
+        atomic_inc(&fs_info->balance_cancel_req);
+        /*
+         * if we are running just wait and return, balance item is
+         * deleted in btrfs_balance in this case
+         */
+        if (atomic_read(&fs_info->balance_running)) {
+                mutex_unlock(&fs_info->balance_mutex);
+                wait_event(fs_info->balance_wait_q,
+                           atomic_read(&fs_info->balance_running) == 0);
+                mutex_lock(&fs_info->balance_mutex);
+        } else {
+                /* __cancel_balance needs volume_mutex */
+                mutex_unlock(&fs_info->balance_mutex);
+                mutex_lock(&fs_info->volume_mutex);
+                mutex_lock(&fs_info->balance_mutex);
+
+                if (fs_info->balance_ctl)
+                        __cancel_balance(fs_info);
+
+                mutex_unlock(&fs_info->volume_mutex);
+        }
+
+        BUG_ON(fs_info->balance_ctl || atomic_read(&fs_info->balance_running));
+        atomic_dec(&fs_info->balance_cancel_req);
+        mutex_unlock(&fs_info->balance_mutex);
+        return 0;
+}
+
 /*
  * shrinking a device means finding all of the device extents past
  * the new size, and then following the back refs to the chunks.
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 80953afb12b9..caa9abd218ef 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -274,6 +274,7 @@ int btrfs_balance(struct btrfs_balance_control *bctl,
                   struct btrfs_ioctl_balance_args *bargs);
 int btrfs_recover_balance(struct btrfs_root *tree_root);
 int btrfs_pause_balance(struct btrfs_fs_info *fs_info);
+int btrfs_cancel_balance(struct btrfs_fs_info *fs_info);
 int btrfs_chunk_readonly(struct btrfs_root *root, u64 chunk_offset);
 int find_free_dev_extent(struct btrfs_trans_handle *trans,
                          struct btrfs_device *device, u64 num_bytes,