[linux-cifs-client] Polished patch to avoid data-loss

[Maximiliano Curia]

On Wednesday 04 January 2006 17:00, you wrote:
> Your patch picked up the other places llseek needs to be exported from (I
> had added those in my testing) - the is size safe to change needs to be
> modified in two ways

I've been polishing the previous patch, and I'm about to put it in production 
for my clients, I would like to hear comments before doing so.

The changes are simple, one to avoid having to set LookCacheEnable to 0, the 
other makes is_size_safe_to_change return 1 when the resource was mounted 
with directio.

It would be nice to have  a "right way" to use mmap over directio, but as I 
only need it to exec elf files, any generic mmap would do what I need.  It 
might be a good idea to use a readonly mmap.

> 1) always allow files open forcedirectio to update file size (no page cache
> issues so should be safe)

> 2) for the default case (local caching, ie using page cache) if file is not
> dirty update the file size if file is dirty write the file data out and
> then update the file size - hard part is we have to check the locking
> around this operation and make sure we match all other locations that could
> be updating the filesize and we may have to lock all potentially affected
> pages (especially the final page in the file if it is a partial page) so we
> don't continue to reuse them.

Well, I didn't mention it before, but, I've also been toying with 
commit_write, avoiding the call to setpagedirty (by calling cifs_write),
so I don't have a pending write behind. And I could not "fix" the data-loss.

But I agree with the proposed changes, anyway.

-- 
Saludos,
 /\/\ /\ >< `/
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