Re: [PATCH 6/10] fuse: Trust kernel i_size only

[Pavel Emelyanov <xemul@parallels.com>]

On 07/04/2012 06:39 PM, Miklos Szeredi wrote:
> Pavel Emelyanov <xemul@parallels.com> writes:
> 
>> Make fuse think that when writeback is on the inode's i_size is alway
>> up-to-date and not update it with the value received from the
>> userspace. This is done because the page cache code may update i_size
>> without letting the FS know.
> 
> Similar rule applies to i_mtime.  Except it's even more tricky, since
> you have to flush the mtime together with the data (the flush should not
> update the modification time).  And we have other operations which also
> change the mtime, and those also need to be updated.
> 
> We should probably look at what NFS is doing.

Miklos,

I've looked at how NFS and FUSE manage the i_mtime.

The NFS (if not looking at the fscache) tries to keep the i_mtime at the
maximum between the local and the remote values. This looks like correct
behavior for FUSE too.

But, looking at the FUSE code I see that the existing attr_version checks
do implement the same approach even if we turn the writeback cache (this
series) ON.

That said, I see no problems with the i_mtime management after this series.
Is there something I've missed?

Thanks,
Pavel