Re: mtdswap + ubi results in deadlock

[Richard Weinberger <richard.weinberger@xxxxxxxxx>]

Emil,

On Tue, Oct 15, 2019 at 7:00 PM Emil Lenngren <emil.lenngren@xxxxxxxxx> wrote:
>
> Hi. I'm trying to use mtdswap together with ubi increase memory.
> Normally mtdswap has its own wear leveling but I want ubi to do that
> job instead. So I removed all wear leveling and oob usage from mtdswap
> (or really it doesn't do wear leveling if the mtd device has no oob)
> and am now using it with a gluebi mtd partition on top of ubi. It
> works good but in some occasions it deadlocks because ubi internally
> uses kmalloc, which in case of low memory, waits for swap to complete.
> But swap won't complete until the data is written to flash.
>
> Do you have any idea how to mitigate this issue?

Well, if you use UBI for swap then no memory allocation within UBI is allowed
to trigger swapping. Otherwise the memory allocation goes into
recursion and locks
up. This is what happens in your case.

You can try to pinpoint these allocations and use GFP_NOFS there but I fear
that will case other problems.

-- 
Thanks,
//richard

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