2 files changed, 28 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d8a669ed5506..ad1a5943a923 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -987,7 +987,8 @@ struct btrfs_dev_replace_item {
 #define BTRFS_BLOCK_GROUP_RAID10        (1ULL << 6)
 #define BTRFS_BLOCK_GROUP_RAID5         (1ULL << 7)
 #define BTRFS_BLOCK_GROUP_RAID6         (1ULL << 8)
-#define BTRFS_BLOCK_GROUP_RESERVED      BTRFS_AVAIL_ALLOC_BIT_SINGLE
+#define BTRFS_BLOCK_GROUP_RESERVED      (BTRFS_AVAIL_ALLOC_BIT_SINGLE | \
+                                         BTRFS_SPACE_INFO_GLOBAL_RSV)
 
 enum btrfs_raid_types {
         BTRFS_RAID_RAID10,
@@ -1019,6 +1020,12 @@ enum btrfs_raid_types {
  */
 #define BTRFS_AVAIL_ALLOC_BIT_SINGLE    (1ULL << 48)
 
+/*
+ * A fake block group type that is used to communicate global block reserve
+ * size to userspace via the SPACE_INFO ioctl.
+ */
+#define BTRFS_SPACE_INFO_GLOBAL_RSV     (1ULL << 49)
+
 #define BTRFS_EXTENDED_PROFILE_MASK     (BTRFS_BLOCK_GROUP_PROFILE_MASK | \
                                          BTRFS_AVAIL_ALLOC_BIT_SINGLE)
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 89d5db7eb452..f2e8fcc279a3 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3562,6 +3562,11 @@ static long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
                 up_read(&info->groups_sem);
         }
 
+        /*
+         * Global block reserve, exported as a space_info
+         */
+        slot_count++;
+
         /* space_slots == 0 means they are asking for a count */
         if (space_args.space_slots == 0) {
                 space_args.total_spaces = slot_count;
@@ -3620,6 +3625,21 @@ static long btrfs_ioctl_space_info(struct btrfs_root *root, void __user *arg)
                 up_read(&info->groups_sem);
         }
 
+        /*
+         * Add global block reserve
+         */
+        if (slot_count) {
+                struct btrfs_block_rsv *block_rsv = &root->fs_info->global_block_rsv;
+
+                spin_lock(&block_rsv->lock);
+                space.total_bytes = block_rsv->size;
+                space.used_bytes = block_rsv->size - block_rsv->reserved;
+                spin_unlock(&block_rsv->lock);
+                space.flags = BTRFS_SPACE_INFO_GLOBAL_RSV;
+                memcpy(dest, &space, sizeof(space));
+                space_args.total_spaces++;
+        }
+
         user_dest = (struct btrfs_ioctl_space_info __user *)
                 (arg + sizeof(struct btrfs_ioctl_space_args));