btrfs: add a trace class for dumping the current ENOSPC state

Often when I'm debugging ENOSPC related issues I have to resort to
printing the entire ENOSPC state with trace_printk() in different spots.
This gets pretty annoying, so add a trace state that does this for us.
Then add a trace point at the end of preemptive flushing so you can see
the state of the space_info when we decide to exit preemptive flushing.
This helped me figure out we weren't kicking in the preemptive flushing
soon enough.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

@@ -1140,6 +1140,7 @@ static void btrfs_preempt_reclaim_metadata_space(struct work_struct *work)
 	/* We only went through once, back off our clamping. */
 	if (loops == 1 && !space_info->reclaim_size)
 		space_info->clamp = max(1, space_info->clamp - 1);
+	trace_btrfs_done_preemptive_reclaim(fs_info, space_info);
 	spin_unlock(&space_info->lock);
 }
 

include/trace/events/btrfs.h

@@ -2029,6 +2029,68 @@ TRACE_EVENT(btrfs_convert_extent_bit,
 		  __print_flags(__entry->clear_bits, "|", EXTENT_FLAGS))
 );
 
+DECLARE_EVENT_CLASS(btrfs_dump_space_info,
+	TP_PROTO(const struct btrfs_fs_info *fs_info,
+		 const struct btrfs_space_info *sinfo),
+
+	TP_ARGS(fs_info, sinfo),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	flags			)
+		__field(	u64,	total_bytes		)
+		__field(	u64,	bytes_used		)
+		__field(	u64,	bytes_pinned		)
+		__field(	u64,	bytes_reserved		)
+		__field(	u64,	bytes_may_use		)
+		__field(	u64,	bytes_readonly		)
+		__field(	u64,	reclaim_size		)
+		__field(	int,	clamp			)
+		__field(	u64,	global_reserved		)
+		__field(	u64,	trans_reserved		)
+		__field(	u64,	delayed_refs_reserved	)
+		__field(	u64,	delayed_reserved	)
+		__field(	u64,	free_chunk_space	)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->flags			=	sinfo->flags;
+		__entry->total_bytes		=	sinfo->total_bytes;
+		__entry->bytes_used		=	sinfo->bytes_used;
+		__entry->bytes_pinned		=	sinfo->bytes_pinned;
+		__entry->bytes_reserved		=	sinfo->bytes_reserved;
+		__entry->bytes_may_use		=	sinfo->bytes_may_use;
+		__entry->bytes_readonly		=	sinfo->bytes_readonly;
+		__entry->reclaim_size		=	sinfo->reclaim_size;
+		__entry->clamp			=	sinfo->clamp;
+		__entry->global_reserved	=	fs_info->global_block_rsv.reserved;
+		__entry->trans_reserved		=	fs_info->trans_block_rsv.reserved;
+		__entry->delayed_refs_reserved	=	fs_info->delayed_refs_rsv.reserved;
+		__entry->delayed_reserved	=	fs_info->delayed_block_rsv.reserved;
+		__entry->free_chunk_space	=	atomic64_read(&fs_info->free_chunk_space);
+	),
+
+	TP_printk_btrfs("flags=%s total_bytes=%llu bytes_used=%llu "
+			"bytes_pinned=%llu bytes_reserved=%llu "
+			"bytes_may_use=%llu bytes_readonly=%llu "
+			"reclaim_size=%llu clamp=%d global_reserved=%llu "
+			"trans_reserved=%llu delayed_refs_reserved=%llu "
+			"delayed_reserved=%llu chunk_free_space=%llu",
+			__print_flags(__entry->flags, "|", BTRFS_GROUP_FLAGS),
+			__entry->total_bytes, __entry->bytes_used,
+			__entry->bytes_pinned, __entry->bytes_reserved,
+			__entry->bytes_may_use, __entry->bytes_readonly,
+			__entry->reclaim_size, __entry->clamp,
+			__entry->global_reserved, __entry->trans_reserved,
+			__entry->delayed_refs_reserved,
+			__entry->delayed_reserved, __entry->free_chunk_space)
+);
+
+DEFINE_EVENT(btrfs_dump_space_info, btrfs_done_preemptive_reclaim,
+	TP_PROTO(const struct btrfs_fs_info *fs_info,
+		 const struct btrfs_space_info *sinfo),
+	TP_ARGS(fs_info, sinfo)
+);
+
 TRACE_EVENT(btrfs_reserve_ticket,
 	TP_PROTO(const struct btrfs_fs_info *fs_info, u64 flags, u64 bytes,
 		 u64 start_ns, int flush, int error),