Re: [Yaffs] data loss under heavy pressure on Yaffs2 GC --> …

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Author: Luc Van Oostenryck
Date:  
To: Charles Manning
CC: yaffs
Subject: Re: [Yaffs] data loss under heavy pressure on Yaffs2 GC --> fix
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