ext4: add more tracepoints and use dev_t in the trace buffer

- Add more ext4 tracepoints.
- Change ext4 tracepoints to use dev_t field with MAJOR/MINOR macros
so that we can save 4 bytes in the ring buffer on some platforms.
- Add sync_mode to ext4_da_writepages, ext4_da_write_pages, and
ext4_da_writepages_result tracepoints. Also remove for_reclaim
field from ext4_da_writepages since it is usually not very useful.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ialloc.c

@@ -152,6 +152,7 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
 	 * We do it here so the bitmap uptodate bit
 	 * get set with buffer lock held.
 	 */
+	trace_ext4_load_inode_bitmap(sb, block_group);
 	set_bitmap_uptodate(bh);
 	if (bh_submit_read(bh) < 0) {
 		put_bh(bh);