netdev - Re: [PATCH net-next 02/10] netdevsim: fib: Perform the route programming in a non-atomic context

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Message-ID: <505125ef-522b-4beb-270f-25b6614f88ed@gmail.com>
Date:   Tue, 26 Jan 2021 21:36:12 -0700
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, amcohen@...dia.com,
        roopa@...dia.com, sharpd@...dia.com, bpoirier@...dia.com,
        mlxsw@...dia.com, Ido Schimmel <idosch@...dia.com>
Subject: Re: [PATCH net-next 02/10] netdevsim: fib: Perform the route
 programming in a non-atomic context

On 1/26/21 6:23 AM, Ido Schimmel wrote:
> From: Amit Cohen <amcohen@...dia.com>
> 
> Currently, netdevsim implements dummy FIB offload and marks notified
> routes with RTM_F_TRAP flag. netdevsim does not defer route notifications
> to a work queue because it does not need to program any hardware.
> 
> Given that netdevsim's purpose is to both give an example implementation
> and allow developers to test their code, align netdevsim to a "real"
> hardware device driver like mlxsw and have it also perform the route
> "programming" in a non-atomic context.
> 
> It will be used to test route flags notifications which will be added in
> the next patches.
> 
> The following changes are needed when route handling is performed in WQ:
> - Handle the accounting in the main context, to be able to return an
>   error for adding route when all the routes are used.
>   For FIB_EVENT_ENTRY_REPLACE increase the counter before scheduling
>   the delayed work, and in case that this event replaces an existing route,
>   decrease the counter as part of the delayed work.
> 
> - For IPv6, cannot use fen6_info->rt->fib6_siblings list because it
>   might be changed during handling the delayed work.
>   Save an array with the nexthops as part of fib6_event struct, and take
>   a reference for each nexthop to prevent them from being freed while
>   event is queued.
> 
> - Change GFP_ATOMIC allocations to GFP_KERNEL.
> 
> - Use single work item that is handling a list of ordered routes.
>   Handling routes must be processed in the order they were submitted to
>   avoid logical errors that could lead to unexpected failures.
> 
> Signed-off-by: Amit Cohen <amcohen@...dia.com>
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
>  drivers/net/netdevsim/fib.c | 467 +++++++++++++++++++++++++-----------
>  1 file changed, 327 insertions(+), 140 deletions(-)
> 

Acked-by: David Ahern <dsahern@...nel.org>