From 251d6a471c831e22880b3c146bb4556ddfb1dc82 Mon Sep 17 00:00:00 2001
From: Wu Fengguang <fengguang.wu@intel.com>
Date: Wed, 1 Dec 2010 17:33:37 -0600
Subject: [PATCH] writeback: trace event writeback_single_inode

It is valuable to know how the dirty inodes are iterated and their IO size.

"writeback_single_inode: bdi 8:0: ino=134246746 state=I_DIRTY_SYNC|I_SYNC age=414 index=0 to_write=1024 wrote=0"

- "state" reflects inode->i_state at the end of writeback_single_inode()
- "index" reflects mapping->writeback_index after the ->writepages() call
- "to_write" is the wbc->nr_to_write at entrance of writeback_single_inode()
- "wrote" is the number of pages actually written

v2: add trace event writeback_single_inode_requeue as proposed by Dave.

CC: Dave Chinner <david@fromorbit.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
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