diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 0ddc114e2aed..2ee73c276acb 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -32,6 +32,12 @@
 #define BITS_PER_BITMAP		(PAGE_CACHE_SIZE * 8)
 #define MAX_CACHE_BYTES_PER_GIG	(32 * 1024)
 
+struct btrfs_trim_range {
+	u64 start;
+	u64 bytes;
+	struct list_head list;
+};
+
 static int link_free_space(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info);
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
@@ -882,6 +888,7 @@ int write_cache_extent_entries(struct io_ctl *io_ctl,
 	int ret;
 	struct btrfs_free_cluster *cluster = NULL;
 	struct rb_node *node = rb_first(&ctl->free_space_offset);
+	struct btrfs_trim_range *trim_entry;
 
 	/* Get the cluster for this block_group if it exists */
 	if (block_group && !list_empty(&block_group->cluster_list)) {
@@ -917,6 +924,21 @@ int write_cache_extent_entries(struct io_ctl *io_ctl,
 			cluster = NULL;
 		}
 	}
+
+	/*
+	 * Make sure we don't miss any range that was removed from our rbtree
+	 * because trimming is running. Otherwise after a umount+mount (or crash
+	 * after committing the transaction) we would leak free space and get
+	 * an inconsistent free space cache report from fsck.
+	 */
+	list_for_each_entry(trim_entry, &ctl->trimming_ranges, list) {
+		ret = io_ctl_add_entry(io_ctl, trim_entry->start,
+				       trim_entry->bytes, NULL);
+		if (ret)
+			goto fail;
+		*entries += 1;
+	}
+
 	return 0;
 fail:
 	return -ENOSPC;
@@ -1136,12 +1158,15 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 
 	io_ctl_set_generation(&io_ctl, trans->transid);
 
+	mutex_lock(&ctl->cache_writeout_mutex);
 	/* Write out the extent entries in the free space cache */
 	ret = write_cache_extent_entries(&io_ctl, ctl,
 					 block_group, &entries, &bitmaps,
 					 &bitmap_list);
-	if (ret)
+	if (ret) {
+		mutex_unlock(&ctl->cache_writeout_mutex);
 		goto out_nospc;
+	}
 
 	/*
 	 * Some spaces that are freed in the current transaction are pinned,
@@ -1149,11 +1174,18 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 	 * committed, we shouldn't lose them.
 	 */
 	ret = write_pinned_extent_entries(root, block_group, &io_ctl, &entries);
-	if (ret)
+	if (ret) {
+		mutex_unlock(&ctl->cache_writeout_mutex);
 		goto out_nospc;
+	}
 
-	/* At last, we write out all the bitmaps. */
+	/*
+	 * At last, we write out all the bitmaps and keep cache_writeout_mutex
+	 * locked while doing it because a concurrent trim can be manipulating
+	 * or freeing the bitmap.
+	 */
 	ret = write_bitmap_entries(&io_ctl, &bitmap_list);
+	mutex_unlock(&ctl->cache_writeout_mutex);
 	if (ret)
 		goto out_nospc;
 
@@ -2296,6 +2328,8 @@ void btrfs_init_free_space_ctl(struct btrfs_block_group_cache *block_group)
 	ctl->start = block_group->key.objectid;
 	ctl->private = block_group;
 	ctl->op = &free_space_op;
+	INIT_LIST_HEAD(&ctl->trimming_ranges);
+	mutex_init(&ctl->cache_writeout_mutex);
 
 	/*
 	 * we only want to have 32k of ram per block group for keeping
@@ -2912,10 +2946,12 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 
 static int do_trimming(struct btrfs_block_group_cache *block_group,
 		       u64 *total_trimmed, u64 start, u64 bytes,
-		       u64 reserved_start, u64 reserved_bytes)
+		       u64 reserved_start, u64 reserved_bytes,
+		       struct btrfs_trim_range *trim_entry)
 {
 	struct btrfs_space_info *space_info = block_group->space_info;
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	int ret;
 	int update = 0;
 	u64 trimmed = 0;
@@ -2935,7 +2971,10 @@ static int do_trimming(struct btrfs_block_group_cache *block_group,
 	if (!ret)
 		*total_trimmed += trimmed;
 
+	mutex_lock(&ctl->cache_writeout_mutex);
 	btrfs_add_free_space(block_group, reserved_start, reserved_bytes);
+	list_del(&trim_entry->list);
+	mutex_unlock(&ctl->cache_writeout_mutex);
 
 	if (update) {
 		spin_lock(&space_info->lock);
@@ -2963,16 +3002,21 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
 	u64 bytes;
 
 	while (start < end) {
+		struct btrfs_trim_range trim_entry;
+
+		mutex_lock(&ctl->cache_writeout_mutex);
 		spin_lock(&ctl->tree_lock);
 
 		if (ctl->free_space < minlen) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
 		entry = tree_search_offset(ctl, start, 0, 1);
 		if (!entry) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
@@ -2981,6 +3025,7 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
 			node = rb_next(&entry->offset_index);
 			if (!node) {
 				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
 				goto out;
 			}
 			entry = rb_entry(node, struct btrfs_free_space,
@@ -2989,6 +3034,7 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
 
 		if (entry->offset >= end) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
@@ -2998,6 +3044,7 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
 		bytes = min(extent_start + extent_bytes, end) - start;
 		if (bytes < minlen) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			goto next;
 		}
 
@@ -3005,9 +3052,13 @@ static int trim_no_bitmap(struct btrfs_block_group_cache *block_group,
 		kmem_cache_free(btrfs_free_space_cachep, entry);
 
 		spin_unlock(&ctl->tree_lock);
+		trim_entry.start = extent_start;
+		trim_entry.bytes = extent_bytes;
+		list_add_tail(&trim_entry.list, &ctl->trimming_ranges);
+		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  extent_start, extent_bytes);
+				  extent_start, extent_bytes, &trim_entry);
 		if (ret)
 			break;
 next:
@@ -3036,17 +3087,21 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
 
 	while (offset < end) {
 		bool next_bitmap = false;
+		struct btrfs_trim_range trim_entry;
 
+		mutex_lock(&ctl->cache_writeout_mutex);
 		spin_lock(&ctl->tree_lock);
 
 		if (ctl->free_space < minlen) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			break;
 		}
 
 		entry = tree_search_offset(ctl, offset, 1, 0);
 		if (!entry) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
 			goto next;
 		}
@@ -3055,6 +3110,7 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
 		ret2 = search_bitmap(ctl, entry, &start, &bytes);
 		if (ret2 || start >= end) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			next_bitmap = true;
 			goto next;
 		}
@@ -3062,6 +3118,7 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
 		bytes = min(bytes, end - start);
 		if (bytes < minlen) {
 			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
 			goto next;
 		}
 
@@ -3070,9 +3127,13 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
 			free_bitmap(ctl, entry);
 
 		spin_unlock(&ctl->tree_lock);
+		trim_entry.start = start;
+		trim_entry.bytes = bytes;
+		list_add_tail(&trim_entry.list, &ctl->trimming_ranges);
+		mutex_unlock(&ctl->cache_writeout_mutex);
 
 		ret = do_trimming(block_group, total_trimmed, start, bytes,
-				  start, bytes);
+				  start, bytes, &trim_entry);
 		if (ret)
 			break;
 next:
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 0cf4977ef70d..88b2238a0aed 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -38,6 +38,8 @@ struct btrfs_free_space_ctl {
 	u64 start;
 	struct btrfs_free_space_op *op;
 	void *private;
+	struct mutex cache_writeout_mutex;
+	struct list_head trimming_ranges;
 };
 
 struct btrfs_free_space_op {
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 4ebd5ebb1ea1..74faea3a516e 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -364,6 +364,8 @@ void btrfs_init_free_ino_ctl(struct btrfs_root *root)
 	ctl->start = 0;
 	ctl->private = NULL;
 	ctl->op = &free_ino_op;
+	INIT_LIST_HEAD(&ctl->trimming_ranges);
+	mutex_init(&ctl->cache_writeout_mutex);
 
 	/*
 	 * Initially we allow to use 16K of ram to cache chunks of