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Commit e7ca2d41 authored by Joern Engel's avatar Joern Engel Committed by Linus Torvalds
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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: default avatarJoern Engel <joern@logfs.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 20420bba

include/linux/fs.h

+4 −4
Original line number Diff line number Diff line
@@ -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?