[PATCH v4 2/3] btrfs: Add trace point for qgroup reserved space

[Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>]

Introduce the following trace points:
qgroup_update_reserve
qgroup_meta_reserve

These trace points are handy to trace qgroup reserve space related
problems.

Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
---
v2:
  None
v3:
  Separate from trace point timing modification patch.
v4:
  Change type casting from "(s64)-num_bytes" to "-(s64)num_bytes".
  Reported by Sanidhya Solanki and David Sterba.
  Change the trace point internal structure from (u64) to (s64).
  Reported by David Sterba.
---
 fs/btrfs/qgroup.c            | 15 +++++++++++++++
 include/trace/events/btrfs.h | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index fc0c64e..aeda450 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1068,6 +1068,8 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info,
 	qgroup->excl += sign * num_bytes;
 	qgroup->excl_cmpr += sign * num_bytes;
 	if (sign > 0) {
+		trace_qgroup_update_reserve(fs_info, qgroup->qgroupid,
+					    qgroup->reserved, -(s64)num_bytes);
 		if (WARN_ON(qgroup->reserved < num_bytes))
 			report_reserved_underflow(fs_info, qgroup,
 						  num_bytes);
@@ -1094,6 +1096,9 @@ static int __qgroup_excl_accounting(struct btrfs_fs_info *fs_info,
 		WARN_ON(sign < 0 && qgroup->excl < num_bytes);
 		qgroup->excl += sign * num_bytes;
 		if (sign > 0) {
+			trace_qgroup_update_reserve(fs_info, qgroup->qgroupid,
+						    qgroup->reserved,
+						    -(s64)num_bytes);
 			if (WARN_ON(qgroup->reserved < num_bytes))
 				report_reserved_underflow(fs_info, qgroup,
 							  num_bytes);
@@ -2178,6 +2183,8 @@ static int qgroup_reserve(struct btrfs_root *root, u64 num_bytes)
 
 		qg = u64_to_ptr(unode->aux);
 
+		trace_qgroup_update_reserve(fs_info, qg->qgroupid,
+					    qg->reserved, num_bytes);
 		qg->reserved += num_bytes;
 	}
 
@@ -2223,6 +2230,8 @@ void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
 
 		qg = u64_to_ptr(unode->aux);
 
+		trace_qgroup_update_reserve(fs_info, qg->qgroupid,
+					    qg->reserved, -(s64)num_bytes);
 		if (WARN_ON(qgroup->reserved < num_bytes))
 			report_reserved_underflow(fs_info, qgroup, num_bytes);
 		else
@@ -2706,6 +2715,8 @@ int btrfs_qgroup_reserve_meta(struct btrfs_root *root, int num_bytes)
 		return 0;
 
 	BUG_ON(num_bytes != round_down(num_bytes, root->nodesize));
+	trace_qgroup_meta_reserve(root->fs_info, root->objectid,
+				  (s64)num_bytes);
 	ret = qgroup_reserve(root, num_bytes);
 	if (ret < 0)
 		return ret;
@@ -2724,6 +2735,8 @@ void btrfs_qgroup_free_meta_all(struct btrfs_root *root)
 	reserved = atomic_xchg(&root->qgroup_meta_rsv, 0);
 	if (reserved == 0)
 		return;
+	trace_qgroup_meta_reserve(root->fs_info, root->objectid,
+				  -(s64)reserved);
 	qgroup_free(root, reserved);
 }
 
@@ -2736,6 +2749,8 @@ void btrfs_qgroup_free_meta(struct btrfs_root *root, int num_bytes)
 	BUG_ON(num_bytes != round_down(num_bytes, root->nodesize));
 	WARN_ON(atomic_read(&root->qgroup_meta_rsv) < num_bytes);
 	atomic_sub(num_bytes, &root->qgroup_meta_rsv);
+	trace_qgroup_meta_reserve(root->fs_info, root->objectid,
+				  -(s64)num_bytes);
 	qgroup_free(root, num_bytes);
 }
 
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index e030d6f..03f3194 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -1468,6 +1468,49 @@ TRACE_EVENT(qgroup_update_counters,
 		  __entry->cur_new_count)
 );
 
+TRACE_EVENT(qgroup_update_reserve,
+
+	TP_PROTO(struct btrfs_fs_info *fs_info, u64 qgid, u64 cur_reserved,
+		 s64 diff),
+
+	TP_ARGS(fs_info, qgid, cur_reserved, diff),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	qgid			)
+		__field(	u64,	cur_reserved		)
+		__field(	s64,	diff			)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->qgid		= qgid;
+		__entry->cur_reserved	= cur_reserved;
+		__entry->diff		= diff;
+	),
+
+	TP_printk_btrfs("qgid = %llu, cur_reserved = %llu, diff = %lld",
+		__entry->qgid, __entry->cur_reserved, __entry->diff)
+);
+
+TRACE_EVENT(qgroup_meta_reserve,
+
+	TP_PROTO(struct btrfs_fs_info *fs_info, u64 refroot, s64 diff),
+
+	TP_ARGS(fs_info, refroot, diff),
+
+	TP_STRUCT__entry_btrfs(
+		__field(	u64,	refroot			)
+		__field(	s64,	diff			)
+	),
+
+	TP_fast_assign_btrfs(fs_info,
+		__entry->refroot	= refroot;
+		__entry->diff		= diff;
+	),
+
+	TP_printk_btrfs("refroot = %llu, diff = %lld",
+		__entry->refroot, __entry->diff)
+);
+
 #endif /* _TRACE_BTRFS_H */
 
 /* This part must be outside protection */
-- 
2.10.2



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