[Yaffs] data loss under heavy pressure on Yaffs2 GC --> fix

[Luc Van Oostenryck]

Charles Manning wrote:
> On Wednesday 03 August 2005 08:46, you wrote:
> 
> 
>>It's not solved for my test.

>>It seems that there is a problem with resizing.
>>
>>Luc
> 
> 
> 
> So this happens in a single run without any unmount/mount between the writing 
> and the reading?  If so, then it is not the problem fixed in 1.15 which 
> required a rescan to make the problem happen.

Yes, it happen whithout remounting (the content of the test file don't change
after a reboot, it's still corrupted).

> To summarize what you report here, the problem is that you'd expect to see 
> holes in the file due to the resize.

The hole are an optimization (no block physically written), but yes it is expected
to read back zeroes.

> Can you run this with more tracing on and see what happens inside YAFFS?

Yes, I'll do. It should be better to have a smaller specific testcase.
I
> don't want to point any fingers yet (not until I see a trace log), but it 
> could be the Linux page cache holding onto data and this being given back. 
> Perhaps there is some page invalidation that needs to happen that is not 
> happening? Perhaps some page is not being released at the correct time?
> 
> -- Charles
> 

Yes, this is certainly a possibility, I will compare with the other file systems
to see what they do with the pages after a truncate/resize.


Luc