ext4: add tracepoint for ext4_journal_start

This will help debug who is responsible for starting a jbd2 transaction.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

2 files changed, 23 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9ea71aa864b3..7910e61809e7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -269,6 +269,7 @@ handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)
         journal_t *journal;
         handle_t  *handle;
 
+        trace_ext4_journal_start(sb, nblocks, _RET_IP_);
         if (sb->s_flags & MS_RDONLY)
                 return ERR_PTR(-EROFS);
 
diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index 5ce2b2f5f524..6f27a59fc90d 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -1520,6 +1520,28 @@ TRACE_EVENT(ext4_load_inode,
                   (unsigned long) __entry->ino)
 );
 
+TRACE_EVENT(ext4_journal_start,
+        TP_PROTO(struct super_block *sb, int nblocks, unsigned long IP),
+
+        TP_ARGS(sb, nblocks, IP),
+
+        TP_STRUCT__entry(
+                __field(        dev_t,  dev                     )
+                __field(          int,  nblocks                 )
+                __field(unsigned long,  ip                      )
+        ),
+
+        TP_fast_assign(
+                __entry->dev     = sb->s_dev;
+                __entry->nblocks = nblocks;
+                __entry->ip      = IP;
+        ),
+
+        TP_printk("dev %d,%d nblocks %d caller %pF",
+                  MAJOR(__entry->dev), MINOR(__entry->dev),
+                  __entry->nblocks, (void *)__entry->ip)
+);
+
 #endif /* _TRACE_EXT4_H */
 
 /* This part must be outside protection */