diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4c48df5..f264edf 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -33,6 +33,7 @@
 #include <asm/kmap_types.h>
 #include <linux/pagemap.h>
 #include <linux/btrfs.h>
+#include <linux/workqueue.h>
 #include "extent_io.h"
 #include "extent_map.h"
 #include "async-thread.h"
@@ -1313,6 +1314,8 @@ struct btrfs_stripe_hash_table {
 
 #define BTRFS_STRIPE_HASH_TABLE_BITS 11
 
+void btrfs_init_async_reclaim_work(struct work_struct *work);
+
 /* fs_info */
 struct reloc_control;
 struct btrfs_device;
@@ -1688,6 +1691,9 @@ struct btrfs_fs_info {
 
 	struct semaphore uuid_tree_rescan_sem;
 	unsigned int update_uuid_tree_gen:1;
+
+	/* Used to reclaim the metadata space in the background. */
+	struct work_struct async_reclaim_work;
 };
 
 struct btrfs_subvolume_writers {
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 029d46c..475889a 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2291,6 +2291,7 @@ int open_ctree(struct super_block *sb,
 	atomic_set(&fs_info->balance_cancel_req, 0);
 	fs_info->balance_ctl = NULL;
 	init_waitqueue_head(&fs_info->balance_wait_q);
+	btrfs_init_async_reclaim_work(&fs_info->async_reclaim_work);
 
 	sb->s_blocksize = 4096;
 	sb->s_blocksize_bits = blksize_bits(4096);
@@ -3603,6 +3604,8 @@ int close_ctree(struct btrfs_root *root)
 	/* clear out the rbtree of defraggable inodes */
 	btrfs_cleanup_defrag_inodes(fs_info);
 
+	cancel_work_sync(&fs_info->async_reclaim_work);
+
 	if (!(fs_info->sb->s_flags & MS_RDONLY)) {
 		ret = btrfs_commit_super(root);
 		if (ret)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1306487..5a5e156 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4201,6 +4201,104 @@ static int flush_space(struct btrfs_root *root,
 
 	return ret;
 }
+
+static inline u64
+btrfs_calc_reclaim_metadata_size(struct btrfs_root *root,
+				 struct btrfs_space_info *space_info)
+{
+	u64 used;
+	u64 expected;
+	u64 to_reclaim;
+
+	to_reclaim = min_t(u64, num_online_cpus() * 1024 * 1024,
+				16 * 1024 * 1024);
+	spin_lock(&space_info->lock);
+	if (can_overcommit(root, space_info, to_reclaim,
+			   BTRFS_RESERVE_FLUSH_ALL)) {
+		to_reclaim = 0;
+		goto out;
+	}
+
+	used = space_info->bytes_used + space_info->bytes_reserved +
+	       space_info->bytes_pinned + space_info->bytes_readonly +
+	       space_info->bytes_may_use;
+	if (can_overcommit(root, space_info, 1024 * 1024,
+			   BTRFS_RESERVE_FLUSH_ALL))
+		expected = div_factor_fine(space_info->total_bytes, 95);
+	else
+		expected = div_factor_fine(space_info->total_bytes, 90);
+
+	if (used > expected)
+		to_reclaim = used - expected;
+	else
+		to_reclaim = 0;
+	to_reclaim = min(to_reclaim, space_info->bytes_may_use +
+				     space_info->bytes_reserved);
+out:
+	spin_unlock(&space_info->lock);
+
+	return to_reclaim;
+}
+
+static inline int need_do_async_reclaim(struct btrfs_space_info *space_info,
+					struct btrfs_fs_info *fs_info, u64 used)
+{
+	return (used >= div_factor_fine(space_info->total_bytes, 98) &&
+		!btrfs_fs_closing(fs_info) &&
+		!test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
+}
+
+static int btrfs_need_do_async_reclaim(struct btrfs_space_info *space_info,
+				       struct btrfs_fs_info *fs_info)
+{
+	u64 used;
+
+	spin_lock(&space_info->lock);
+	used = space_info->bytes_used + space_info->bytes_reserved +
+	       space_info->bytes_pinned + space_info->bytes_readonly +
+	       space_info->bytes_may_use;
+	if (need_do_async_reclaim(space_info, fs_info, used)) {
+		spin_unlock(&space_info->lock);
+		return 1;
+	}
+	spin_unlock(&space_info->lock);
+
+	return 0;
+}
+
+static void btrfs_async_reclaim_metadata_space(struct work_struct *work)
+{
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_space_info *space_info;
+	u64 to_reclaim;
+	int flush_state;
+
+	fs_info = container_of(work, struct btrfs_fs_info, async_reclaim_work);
+	space_info = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
+
+	to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info->fs_root,
+						      space_info);
+	if (!to_reclaim)
+		return;
+
+	flush_state = FLUSH_DELAYED_ITEMS_NR;
+	do {
+		flush_space(fs_info->fs_root, space_info, to_reclaim,
+			    to_reclaim, flush_state);
+		flush_state++;
+		if (!btrfs_need_do_async_reclaim(space_info, fs_info))
+			return;
+	} while (flush_state <= COMMIT_TRANS);
+
+	if (btrfs_need_do_async_reclaim(space_info, fs_info))
+		queue_work(system_unbound_wq, work);
+}
+
+void btrfs_init_async_reclaim_work(struct work_struct *work)
+{
+	INIT_WORK(work, btrfs_async_reclaim_metadata_space);
+}
+
 /**
  * reserve_metadata_bytes - try to reserve bytes from the block_rsv's space
  * @root - the root we're allocating for
@@ -4308,8 +4406,13 @@ again:
 	if (ret && flush != BTRFS_RESERVE_NO_FLUSH) {
 		flushing = true;
 		space_info->flush = 1;
+	} else if (!ret && space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
+		used += orig_bytes;
+		if (need_do_async_reclaim(space_info, root->fs_info, used) &&
+		    !work_busy(&root->fs_info->async_reclaim_work))
+			queue_work(system_unbound_wq,
+				   &root->fs_info->async_reclaim_work);
 	}
-
 	spin_unlock(&space_info->lock);
 
 	if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 5011aad..99607b6 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1423,6 +1423,7 @@ static int btrfs_remount(struct super_block *sb, int *flags, char *data)
 		 * this also happens on 'umount -rf' or on shutdown, when
 		 * the filesystem is busy.
 		 */
+		cancel_work_sync(&fs_info->async_reclaim_work);
 
 		/* wait for the uuid_scan task to finish */
 		down(&fs_info->uuid_tree_rescan_sem);
