btrfs: export global block reserve size as space_info

Introduce a block group type bit for a global reserve and fill the space
info for SPACE_INFO ioctl. This should replace the newly added ioctl
(01e219e8069516cdb98594d417b8bb8d906ed30d) to get just the 'size' part
of the global reserve, while the actual usage can be now visible in the
'btrfs fi df' output during ENOSPC stress.

The unpatched userspace tools will show the blockgroup as 'unknown'.

CC: Jeff Mahoney <jeffm@suse.com>
CC: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 89d5db7..f2e8fcc 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));