Document I_SYNC and I_DATASYNC
PATCH 1/1 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 Jörn Engel <[email protected]>
---
include/linux/fs.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
include/linux/fs.h renamed from include/linux/fs.h~I_DIRTY +4 -4
@@ -1276,8 +1276,10 @@ 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().
@@ -1309,8 +1311,6 @@ 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?