btrfs: factor out btrfs_return_free_space()

Factor out a part of unpin_extent_range() that returns space back to the
space info, prioritizing global block reserve.  Also, move the "len"
variable into the loop to clarify we don't need to carry it beyond an
iteration.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 255e85f78313..8b6340c59bf2 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -2082,3 +2082,32 @@ void btrfs_reclaim_sweep(const struct btrfs_fs_info *fs_info)
 			do_reclaim_sweep(space_info, raid);
 	}
 }
+
+void btrfs_return_free_space(struct btrfs_space_info *space_info, u64 len)
+{
+	struct btrfs_fs_info *fs_info = space_info->fs_info;
+	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
+
+	lockdep_assert_held(&space_info->lock);
+
+	/* Prioritize the global reservation to receive the freed space. */
+	if (global_rsv->space_info != space_info)
+		goto grant;
+
+	spin_lock(&global_rsv->lock);
+	if (!global_rsv->full) {
+		u64 to_add = min(len, global_rsv->size - global_rsv->reserved);
+
+		global_rsv->reserved += to_add;
+		btrfs_space_info_update_bytes_may_use(fs_info, space_info, to_add);
+		if (global_rsv->reserved >= global_rsv->size)
+			global_rsv->full = 1;
+		len -= to_add;
+	}
+	spin_unlock(&global_rsv->lock);
+
+grant:
+	/* Add to any tickets we may have. */
+	if (len)
+		btrfs_try_granting_tickets(fs_info, space_info);
+}