btrfs: print available space for a block group when dumping a space info

When dumping a space info, we iterate over all its block groups and then
print their size and the amounts of bytes used, reserved, pinned, etc.
When debugging -ENOSPC problems it's also useful to know how much space
is available (free), so calculate that and print it as well.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index ae12a8a..54d78e8 100644 (file)
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -523,13 +523,18 @@ void btrfs_dump_space_info(struct btrfs_fs_info *fs_info,
        down_read(&info->groups_sem);
 again:
        list_for_each_entry(cache, &info->block_groups[index], list) {
+               u64 avail;
+
                spin_lock(&cache->lock);
+               avail = cache->length - cache->used - cache->pinned -
+                       cache->reserved - cache->delalloc_bytes -
+                       cache->bytes_super - cache->zone_unusable;
                btrfs_info(fs_info,
-"block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %llu delalloc %llu super %llu zone_unusable %s",
+"block group %llu has %llu bytes, %llu used %llu pinned %llu reserved %llu delalloc %llu super %llu zone_unusable (%llu bytes available) %s",
                           cache->start, cache->length, cache->used, cache->pinned,
                           cache->reserved, cache->delalloc_bytes,
                           cache->bytes_super, cache->zone_unusable,
-                          cache->ro ? "[readonly]" : "");
+                          avail, cache->ro ? "[readonly]" : "");
                spin_unlock(&cache->lock);
                btrfs_dump_free_space(cache, bytes);
        }