Re: + switch-ntfs-to-touch_atime.patch added to -mm tree

[Anton Altaparmakov <aia21@cam.ac.uk>]

On Tue, 8 Nov 2005, Christoph Hellwig wrote:
> [ccing -fsdevel now because this is something of interest to the public]
> 
> On Mon, Nov 07, 2005 at 09:51:08PM +0000, Anton Altaparmakov wrote:
> > What callers are those?  I am curious...  The SUS/Posix standard requires 
> > it as I said in previous post (except for the no size change case but 
> > as I also said in previous post the VFS does that wrong in same way as 
> > ntfs and I just copied vfs)...
> 
> Besides the various ->setattr instaces which are supposed to set ctime if
> ATTR_SIZE|ATTR_CTIME are set (which it is for sys_truncate or
> sys_ftruncate but possibly not nfsd requests) generic_file_buffered_write()
> calls vmtruncate and thus ->truncate without asking for ctime updates.

ntfs doesn't use generic_file_buffered_write() but yes the ntfs version 
also does it (or will do if it doesn't yet - I had taken it out and 
can't remember if I had put it back in yet)...

> The point here is to repeat that the nth time is that you are doing
> things in ->truncate that you shouldn't do there.  Just move your
> updates of the base inode to ->setattr, and update ->i_ctime directly
> like all the other filesystems do instead of using inode_update_time
> which contains an optimization that's only usefull for a codepath like
> write where the ctime/mtime update happens very frequently.

Ok, will do.

> Your use of the function is wrong no matter whether it takes a struct
> file or struct inode.
> 
> > > so just update them directly for those callers.
> > 
> > That is difficult to do as VFS ->truncate() does not allow an error to be 
> > returned.  And the setting must only happen on success for {f,}truncate().
> > 
> > Thus vmtruncate() always returns success even when ->truncate() failed, so 
> > VFS _cannot_ be compliant with standard unless it is changed so that 
> > ->truncate() can return error and vmtruncate() passes that upward to 
> > ->setattr().  Otherwise you have to do the cmtime updates from 
> > ->truncate() on success and not do them on failure.
> 
> so please submit a patch to allow an error return from ->truncate.

As I said I don't care about conforming to standards.  I just want to do 
same as all other Linux fs.  I have enough to do as it is without 
working on and submitting random patches...

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/