Btrfs: introduce btrfs_{start, end}_nocow_write() for each subvolume

[firefly-linux-kernel-4.4.55.git] / fs / btrfs / ioctl.c

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 1ae45bd9d27d51d15a511b85ad5a520e54c1dd65..57bc9f33fa3c6d5b3f6d7ffc0d50821ac183d436 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -611,6 +611,23 @@ fail:
        return ret;
 }
 
+static void btrfs_wait_nocow_write(struct btrfs_root *root)
+{
+       s64 writers;
+       DEFINE_WAIT(wait);
+
+       do {
+               prepare_to_wait(&root->subv_writers->wait, &wait,
+                               TASK_UNINTERRUPTIBLE);
+
+               writers = percpu_counter_sum(&root->subv_writers->counter);
+               if (writers)
+                       schedule();
+
+               finish_wait(&root->subv_writers->wait, &wait);
+       } while (writers);
+}
+
 static int create_snapshot(struct btrfs_root *root, struct inode *dir,
                           struct dentry *dentry, char *name, int namelen,
                           u64 *async_transid, bool readonly,
@@ -624,15 +641,21 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
        if (!root->ref_cows)
                return -EINVAL;
 
+       atomic_inc(&root->will_be_snapshoted);
+       smp_mb__after_atomic_inc();
+       btrfs_wait_nocow_write(root);
+
        ret = btrfs_start_delalloc_inodes(root, 0);
        if (ret)
-               return ret;
+               goto out;
 
        btrfs_wait_ordered_extents(root, -1);
 
        pending_snapshot = kzalloc(sizeof(*pending_snapshot), GFP_NOFS);
-       if (!pending_snapshot)
-               return -ENOMEM;
+       if (!pending_snapshot) {
+               ret = -ENOMEM;
+               goto out;
+       }
 
        btrfs_init_block_rsv(&pending_snapshot->block_rsv,
                             BTRFS_BLOCK_RSV_TEMP);
@@ -649,7 +672,7 @@ static int create_snapshot(struct btrfs_root *root, struct inode *dir,
                                        &pending_snapshot->qgroup_reserved,
                                        false);
        if (ret)
-               goto out;
+               goto free;
 
        pending_snapshot->dentry = dentry;
        pending_snapshot->root = root;
@@ -700,8 +723,10 @@ fail:
        btrfs_subvolume_release_metadata(BTRFS_I(dir)->root,
                                         &pending_snapshot->block_rsv,
                                         pending_snapshot->qgroup_reserved);
-out:
+free:
        kfree(pending_snapshot);
+out:
+       atomic_dec(&root->will_be_snapshoted);
        return ret;
 }