ext4: Add new tracepoint: trace_ext4_da_write_pages()

Add a new tracepoint which shows the pages that will be written using
write_cache_pages() by ext4_da_writepages().
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -113,6 +113,21 @@ struct ext4_allocation_request {
 	unsigned int flags;
 };
 
+/*
+ * For delayed allocation tracking
+ */
+struct mpage_da_data {
+	struct inode *inode;
+	sector_t b_blocknr;		/* start block number of extent */
+	size_t b_size;			/* size of extent */
+	unsigned long b_state;		/* state of the extent */
+	unsigned long first_page, next_page;	/* extent of pages */
+	struct writeback_control *wbc;
+	int io_done;
+	int pages_written;
+	int retval;
+};
+
 /*
  * Special inodes numbers
  */

fs/ext4/inode.c

@@ -1875,18 +1875,6 @@ static void ext4_da_page_release_reservation(struct page *page,
  * Delayed allocation stuff
  */
 
-struct mpage_da_data {
-	struct inode *inode;
-	sector_t b_blocknr;		/* start block number of extent */
-	size_t b_size;			/* size of extent */
-	unsigned long b_state;		/* state of the extent */
-	unsigned long first_page, next_page;	/* extent of pages */
-	struct writeback_control *wbc;
-	int io_done;
-	int pages_written;
-	int retval;
-};
-
 /*
  * mpage_da_submit_io - walks through extent of pages and try to write
  * them with writepage() call back
@@ -2863,6 +2851,7 @@ static int ext4_da_writepages(struct address_space *mapping,
 			mpd.io_done = 1;
 			ret = MPAGE_DA_EXTENT_TAIL;
 		}
+		trace_ext4_da_write_pages(inode, &mpd);
 		wbc->nr_to_write -= mpd.pages_written;
 
 		ext4_journal_stop(handle);

include/trace/events/ext4.h

@@ -251,6 +251,40 @@ TRACE_EVENT(ext4_da_writepages,
 		  __entry->range_cyclic)
 );
 
+TRACE_EVENT(ext4_da_write_pages,
+	TP_PROTO(struct inode *inode, struct mpage_da_data *mpd),
+
+	TP_ARGS(inode, mpd),
+
+	TP_STRUCT__entry(
+		__field(	dev_t,	dev			)
+		__field(	ino_t,	ino			)
+		__field(	__u64,	b_blocknr		)
+		__field(	__u32,	b_size			)
+		__field(	__u32,	b_state			)
+		__field(	unsigned long,	first_page	)
+		__field(	int,	io_done			)
+		__field(	int,	pages_written		)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= inode->i_sb->s_dev;
+		__entry->ino		= inode->i_ino;
+		__entry->b_blocknr	= mpd->b_blocknr;
+		__entry->b_size		= mpd->b_size;
+		__entry->b_state	= mpd->b_state;
+		__entry->first_page	= mpd->first_page;
+		__entry->io_done	= mpd->io_done;
+		__entry->pages_written	= mpd->pages_written;
+	),
+
+	TP_printk("dev %s ino %lu b_blocknr %llu b_size %u b_state 0x%04x first_page %lu io_done %d pages_written %d",
+		  jbd2_dev_to_name(__entry->dev), __entry->ino,
+		  __entry->b_blocknr, __entry->b_size,
+		  __entry->b_state, __entry->first_page,
+		  __entry->io_done, __entry->pages_written)
+);
+
 TRACE_EVENT(ext4_da_writepages_result,
 	TP_PROTO(struct inode *inode, struct writeback_control *wbc,
 			int ret, int pages_written),