FDS init with 2 pages labeled as swap

[Anthony Ambuehl]

I have an found a problem where I find FDS has 2 pages labeled as swap, which results in loss of one of the data pages.

my configuration is 2 data pages and 1 swap page.  at start up, the pages show 1 data page and 2 swap pages.

after init the swap is not completed and only 1 data page is found.  the second entry in m_pages has an p_addr of 0

I presume this occurred when a reset interrupted a page swap.  

Is there any existing fix for this condition?

I'm using SDK 15.0.0 however I have backported/pactched FDS with fixes from 15.3.0

[Anthony Ambuehl]

Hello Edvin,   

I stepped through the pages_init function and verified the page_type had 2 pages with FDS_PAGE_SWAP and only 1 page with FDS_PAGE_DATA.  After this occurred only 1 entry in m_pages was initialized.

Unfortunately after getting this far in the debug, I erased the device since I was trying to complete a feature before the end of the day.  I realize now saving off the complete flash would have been a really good idea.   I'll look at backporting the changes to FDS from SDK17, which will be a low risk versus completely upgrading the sdk for our production devices.

a*

[Edvin]

I see.

I think it is a good idea to backport the FDS, as it contains some bug fixes. 

Another thing that is worth mentioning is that you should only call fds_gc() in cases where you receive events indicating that the FDS is full. Don't do so by default on startup of the application. We see a lot of customers doing this, as they think it is a good idea.

The reason this is a bad idea is that if this is a battery powered device, you may experience a lot of resets when the battery is running out, causing many (!) fds_gc() to be called, and many aborted during power cuts. This behavior will provoke any potential bugs in the FDS regarding fds_gc(). 

So please don't call fds_gc() in the startup of your application. Only if the FDS is in fact full.

Best regards,

Edvin