introduce I_SYNC

I_LOCK was used for several unrelated purposes, which caused deadlock
situations in certain filesystems as a side effect.  One of the purposes
now uses the new I_SYNC bit.

Also document the various bits and change their order from historical to
logical.

[bunk@stusta.de: make fs/inode.c:wake_up_inode() static]
Signed-off-by: Joern Engel <joern@wohnheim.fh-wedel.de>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: David Chinner <dgc@sgi.com>
Cc: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Al Viro <viro@ftp.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bcdbbf6..d8c21e5 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -37,7 +37,7 @@
 
 /*
  * The maximum number of pages to writeout in a single bdflush/kupdate
- * operation.  We do this so we don't hold I_LOCK against an inode for
+ * operation.  We do this so we don't hold I_SYNC against an inode for
  * enormous amounts of time, which would block a userspace task which has
  * been forced to throttle against that inode.  Also, the code reevaluates
  * the dirty each time it has written this many pages.