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Document I_SYNC and I_DATASYNC

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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>
This commit is contained in:
Joern Engel 2008-02-06 01:36:59 -08:00 committed by Linus Torvalds
parent 20420bba13
commit e7ca2d41a0
1 changed files with 4 additions and 4 deletions
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include/linux/fs.h
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@ -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?