vfs: add explanation of I_DIRTY_DATASYNC bit
Add explanation of I_DIRTY_DATASYNC bit.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Joern Engel <joern@logfs.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 18cfbf7..98ffb6e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1284,8 +1284,10 @@
*
* 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_DATASYNC Data-related inode changes pending. We keep track of
+ * these changes separately from I_DIRTY_SYNC so that we
+ * don't have to write inode on fdatasync() when only
+ * mtime has changed in it.
* 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().