ext4: enhance tracepoints during the folios writeback

commit 6b13275 upstream.

After mpage_map_and_submit_extent() supports restarting handle if
credits are insufficient during allocating blocks, it is more likely to
exit the current mapping iteration and continue to process the current
processing partially mapped folio again. The existing tracepoints are
not sufficient to track this situation, so enhance the tracepoints to
track the writeback position and the return value before and after
submitting the folios.

Signed-off-by: Zhang Yi <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: zhangyi089

fs/ext4/inode.c

@@ -2936,7 +2936,8 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
 		}
 		mpd->do_map = 1;
 
-		trace_ext4_da_write_pages(inode, mpd->start_pos, wbc);
+		trace_ext4_da_write_folios_start(inode, mpd->start_pos,
+				mpd->next_pos, wbc);
 		ret = mpage_prepare_extent_to_map(mpd);
 		if (!ret && mpd->map.m_len)
 			ret = mpage_map_and_submit_extent(handle, mpd,
@@ -2974,6 +2975,8 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
 		} else
 			ext4_put_io_end(mpd->io_submit.io_end);
 		mpd->io_submit.io_end = NULL;
+		trace_ext4_da_write_folios_end(inode, mpd->start_pos,
+				mpd->next_pos, wbc, ret);
 
 		if (ret == -ENOSPC && sbi->s_journal) {
 			/*

include/trace/events/ext4.h

@@ -482,16 +482,17 @@ TRACE_EVENT(ext4_writepages,
 		  (unsigned long) __entry->writeback_index)
 );
 
-TRACE_EVENT(ext4_da_write_pages,
-	TP_PROTO(struct inode *inode, loff_t start_pos,
+TRACE_EVENT(ext4_da_write_folios_start,
+	TP_PROTO(struct inode *inode, loff_t start_pos, loff_t next_pos,
 		 struct writeback_control *wbc),
 
-	TP_ARGS(inode, start_pos, wbc),
+	TP_ARGS(inode, start_pos, next_pos, wbc),
 
 	TP_STRUCT__entry(
 		__field(	dev_t,	dev			)
 		__field(	ino_t,	ino			)
 		__field(       loff_t,	start_pos		)
+		__field(       loff_t,	next_pos		)
 		__field(	 long,	nr_to_write		)
 		__field(	  int,	sync_mode		)
 	),
@@ -500,16 +501,47 @@ TRACE_EVENT(ext4_da_write_pages,
 		__entry->dev		= inode->i_sb->s_dev;
 		__entry->ino		= inode->i_ino;
 		__entry->start_pos	= start_pos;
+		__entry->next_pos	= next_pos;
 		__entry->nr_to_write	= wbc->nr_to_write;
 		__entry->sync_mode	= wbc->sync_mode;
 	),
 
-	TP_printk("dev %d,%d ino %lu start_pos 0x%llx nr_to_write %ld sync_mode %d",
+	TP_printk("dev %d,%d ino %lu start_pos 0x%llx next_pos 0x%llx nr_to_write %ld sync_mode %d",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
-		  (unsigned long) __entry->ino, __entry->start_pos,
+		  (unsigned long) __entry->ino, __entry->start_pos, __entry->next_pos,
 		  __entry->nr_to_write, __entry->sync_mode)
 );
 
+TRACE_EVENT(ext4_da_write_folios_end,
+	TP_PROTO(struct inode *inode, loff_t start_pos, loff_t next_pos,
+		 struct writeback_control *wbc, int ret),
+
+	TP_ARGS(inode, start_pos, next_pos, wbc, ret),
+
+	TP_STRUCT__entry(
+		__field(	dev_t,	dev			)
+		__field(	ino_t,	ino			)
+		__field(       loff_t,	start_pos		)
+		__field(       loff_t,	next_pos		)
+		__field(	 long,	nr_to_write		)
+		__field(	  int,	ret			)
+	),
+
+	TP_fast_assign(
+		__entry->dev		= inode->i_sb->s_dev;
+		__entry->ino		= inode->i_ino;
+		__entry->start_pos	= start_pos;
+		__entry->next_pos	= next_pos;
+		__entry->nr_to_write	= wbc->nr_to_write;
+		__entry->ret		= ret;
+	),
+
+	TP_printk("dev %d,%d ino %lu start_pos 0x%llx next_pos 0x%llx nr_to_write %ld ret %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long) __entry->ino, __entry->start_pos, __entry->next_pos,
+		  __entry->nr_to_write, __entry->ret)
+);
+
 TRACE_EVENT(ext4_da_write_pages_extent,
 	TP_PROTO(struct inode *inode, struct ext4_map_blocks *map),