Btrfs: add tracepoints for flush events

We want to track when we're triggering flushing from our reservation code and
what flushing is being done when we start flushing.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

2 files changed, 21 insertions, 10 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 2e04c9d6f21d..83a6a931af09 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2626,6 +2626,15 @@ enum btrfs_reserve_flush_enum {
         BTRFS_RESERVE_FLUSH_ALL,
 };
 
+enum btrfs_flush_state {
+        FLUSH_DELAYED_ITEMS_NR  =       1,
+        FLUSH_DELAYED_ITEMS     =       2,
+        FLUSH_DELALLOC          =       3,
+        FLUSH_DELALLOC_WAIT     =       4,
+        ALLOC_CHUNK             =       5,
+        COMMIT_TRANS            =       6,
+};
+
 int btrfs_check_data_free_space(struct inode *inode, u64 start, u64 len);
 int btrfs_alloc_data_chunk_ondemand(struct inode *inode, u64 bytes);
 void btrfs_free_reserved_data_space(struct inode *inode, u64 start, u64 len);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5d24ec44d99b..31ded6aae1f0 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4835,15 +4835,6 @@ commit:
         return btrfs_commit_transaction(trans, root);
 }
 
-enum flush_state {
-        FLUSH_DELAYED_ITEMS_NR  =       1,
-        FLUSH_DELAYED_ITEMS     =       2,
-        FLUSH_DELALLOC          =       3,
-        FLUSH_DELALLOC_WAIT     =       4,
-        ALLOC_CHUNK             =       5,
-        COMMIT_TRANS            =       6,
-};
-
 struct reserve_ticket {
         u64 bytes;
         int error;
@@ -4901,6 +4892,8 @@ static int flush_space(struct btrfs_root *root,
                 break;
         }
 
+        trace_btrfs_flush_space(root->fs_info, space_info->flags, num_bytes,
+                                orig_bytes, state, ret);
         return ret;
 }
 
@@ -5178,6 +5171,10 @@ static int __reserve_metadata_bytes(struct btrfs_root *root,
                         list_add_tail(&ticket.list, &space_info->tickets);
                         if (!space_info->flush) {
                                 space_info->flush = 1;
+                                trace_btrfs_trigger_flush(root->fs_info,
+                                                          space_info->flags,
+                                                          orig_bytes, flush,
+                                                          "enospc");
                                 queue_work(system_unbound_wq,
                                            &root->fs_info->async_reclaim_work);
                         }
@@ -5194,9 +5191,14 @@ static int __reserve_metadata_bytes(struct btrfs_root *root,
                  */
                 if (!root->fs_info->log_root_recovering &&
                     need_do_async_reclaim(space_info, root->fs_info, used) &&
-                    !work_busy(&root->fs_info->async_reclaim_work))
+                    !work_busy(&root->fs_info->async_reclaim_work)) {
+                        trace_btrfs_trigger_flush(root->fs_info,
+                                                  space_info->flags,
+                                                  orig_bytes, flush,
+                                                  "preempt");
                         queue_work(system_unbound_wq,
                                    &root->fs_info->async_reclaim_work);
+                }
         }
         spin_unlock(&space_info->lock);
         if (!ret || flush == BTRFS_RESERVE_NO_FLUSH)