fs/fs-writeback.c: inode writeback list tracking tracepoints

The per-sb inode writeback list tracks inodes currently under writeback
to facilitate efficient sync processing.  In particular, it ensures that
sync only needs to walk through a list of inodes that were cleaned by
the sync.

Add a couple tracepoints to help identify when inodes are added/removed
to and from the writeback lists.  Piggyback off of the writeback
lazytime tracepoint template as it already tracks the relevant inode
information.

Link: http://lkml.kernel.org/r/1466594593-6757-3-git-send-email-bfoster@redhat.com
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <dchinner@redhat.com>
cc: Josef Bacik <jbacik@fb.com>
Cc: Holger Hoffstätte <holger.hoffstaette@applied-asynchrony.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 1fcce8345da3..6f9c9f6f5157 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -990,8 +990,10 @@ void sb_mark_inode_writeback(struct inode *inode)
 
         if (list_empty(&inode->i_wb_list)) {
                 spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
-                if (list_empty(&inode->i_wb_list))
+                if (list_empty(&inode->i_wb_list)) {
                         list_add_tail(&inode->i_wb_list, &sb->s_inodes_wb);
+                        trace_sb_mark_inode_writeback(inode);
+                }
                 spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
         }
 }
@@ -1006,7 +1008,10 @@ void sb_clear_inode_writeback(struct inode *inode)
 
         if (!list_empty(&inode->i_wb_list)) {
                 spin_lock_irqsave(&sb->s_inode_wblist_lock, flags);
-                list_del_init(&inode->i_wb_list);
+                if (!list_empty(&inode->i_wb_list)) {
+                        list_del_init(&inode->i_wb_list);
+                        trace_sb_clear_inode_writeback(inode);
+                }
                 spin_unlock_irqrestore(&sb->s_inode_wblist_lock, flags);
         }
 }