From e7ca2d41a029577a8cff453d1445951d4f96bfd8 Mon Sep 17 00:00:00 2001
From: Joern Engel <joern@logfs.org>
Date: Wed, 6 Feb 2008 01:36:59 -0800
Subject: [PATCH] Document I_SYNC and I_DATASYNC
After some archeology (see http://logfs.org/logfs/inode_state_bits) I
finally figured out what the three I_DIRTY bits do. Maybe others would
prefer less effort to reach this insight.
Signed-off-by: Joern Engel <joern@logfs.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/fs.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ed289a9c5ccbc..e260d9a32c218 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1279,8 +1279,10 @@ struct super_operations {
*
* Two bits are used for locking and completion notification, I_LOCK and I_SYNC.
*
- * I_DIRTY_SYNC Inode itself is dirty.
- * I_DIRTY_DATASYNC Data-related inode changes pending
+ * I_DIRTY_SYNC Inode is dirty, but doesn't have to be written on
+ * fdatasync(). i_atime is the usual cause.
+ * I_DIRTY_DATASYNC Inode is dirty and must be written on fdatasync(), f.e.
+ * because i_size changed.
* I_DIRTY_PAGES Inode has dirty pages. Inode itself may be clean.
* I_NEW get_new_inode() sets i_state to I_LOCK|I_NEW. Both
* are cleared by unlock_new_inode(), called from iget().
@@ -1312,8 +1314,6 @@ struct super_operations {
* purpose reduces latency and prevents some filesystem-
* specific deadlocks.
*
- * Q: Why does I_DIRTY_DATASYNC exist? It appears as if it could be replaced
- * by (I_DIRTY_SYNC|I_DIRTY_PAGES).
* Q: What is the difference between I_WILL_FREE and I_FREEING?
* Q: igrab() only checks on (I_FREEING|I_WILL_FREE). Should it also check on
* I_CLEAR? If not, why?
--
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