netdev - Re: [PATCH net 1/5] net: tls: handle -EBUSY on async encrypt/decrypt requests

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Date: Tue, 12 Sep 2023 12:43:32 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: netdev@...r.kernel.org, davejwatson@...com, kuba@...nel.org,
	vakul.garg@....com, borisp@...dia.com, john.fastabend@...il.com
Subject: Re: [PATCH net 1/5] net: tls: handle -EBUSY on async encrypt/decrypt
 requests

On Fri, Sep 08, 2023 at 05:55:59PM +0200, Sabrina Dubroca wrote:
>
> Uh, ok, I didn't know that, thanks for explaining. When I was fixing
> this code I couldn't find a mention of what the expectations for
> MAY_BACKLOG are. Could you add a comment describing this in the
> headers (either for #define CRYPTO_TFM_REQ_MAY_BACKLOG or
> aead_request_set_callback, wherever is more appropriate). MAY_BACKLOG
> is used by both tls and tipc (talking only about networking) and
> neither seem to respect this need to back off.

Patches are welcome :)

A bit of history: at the beginning we always dropped requests
that we couldn't queue because the only user was IPsec so this
is the expected behaviour.

When storage crypto support was added there was a need for reliable
handling of resource constraints so that's why MAY_BACKLOG was added.
However, the expectation is obviously that you must stop sending new
requests once you run into the resource constraint.

> Jakub, I guess we should drop the CRYPTO_TFM_REQ_MAY_BACKLOG for net,
> and maybe consider adding it back (with the back off) in
> net-next. Probably not urgent considering that nobody seems to have
> run into this bug so far.

I think that would be the prudent action.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt