netdev - Re: [PATCH net-next v2] net: sched: flower: refactor reoffload for concurrent access

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Message-Id: <20190424.115352.862921093841832872.davem@davemloft.net>
Date:   Wed, 24 Apr 2019 11:53:52 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     vladbu@...lanox.com
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, jakub.kicinski@...ronome.com
Subject: Re: [PATCH net-next v2] net: sched: flower: refactor reoffload for
 concurrent access

From: Vlad Buslov <vladbu@...lanox.com>
Date: Wed, 24 Apr 2019 09:53:31 +0300

> Recent changes that introduced unlocked flower did not properly account for
> case when reoffload is initiated concurrently with filter updates. To fix
> the issue, extend flower with 'hw_filters' list that is used to store
> filters that don't have 'skip_hw' flag set. Filter is added to the list
> when it is inserted to hardware and only removed from it after being
> unoffloaded from all drivers that parent block is attached to. This ensures
> that concurrent reoffload can still access filter that is being deleted and
> prevents race condition when driver callback can be removed when filter is
> no longer accessible trough idr, but is still present in hardware.
> 
> Refactor fl_change() to respect new filter reference counter and to release
> filter reference with __fl_put() in case of error, instead of directly
> deallocating filter memory. This allows for concurrent access to filter
> from fl_reoffload() and protects it with reference counting. Refactor
> fl_reoffload() to iterate over hw_filters list instead of idr. Implement
> fl_get_next_hw_filter() helper function that is used to iterate over
> hw_filters list with reference counting and skips filters that are being
> concurrently deleted.
> 
> Fixes: 92149190067d ("net: sched: flower: set unlocked flag for flower proto ops")
> Signed-off-by: Vlad Buslov <vladbu@...lanox.com>

Applied, thank you.