linux-kernel - Re: [PATCH v2] xen-netback: fix occasional leak of grant ref mappings under memory pressure

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Message-Id: <20190228.103713.745079321072396223.davem@davemloft.net>
Date:   Thu, 28 Feb 2019 10:37:13 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     igor.druzhinin@...rix.com
Cc:     xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, wei.liu2@...rix.com,
        paul.durrant@...rix.com
Subject: Re: [PATCH v2] xen-netback: fix occasional leak of grant ref
 mappings under memory pressure

From: Igor Druzhinin <igor.druzhinin@...rix.com>
Date: Thu, 28 Feb 2019 12:48:03 +0000

> Zero-copy callback flag is not yet set on frag list skb at the moment
> xenvif_handle_frag_list() returns -ENOMEM. This eventually results in
> leaking grant ref mappings since xenvif_zerocopy_callback() is never
> called for these fragments. Those eventually build up and cause Xen
> to kill Dom0 as the slots get reused for new mappings:
> 
> "d0v0 Attempt to implicitly unmap a granted PTE c010000329fce005"
> 
> That behavior is observed under certain workloads where sudden spikes
> of page cache writes coexist with active atomic skb allocations from
> network traffic. Additionally, rework the logic to deal with frag_list
> deallocation in a single place.
> 
> Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> Signed-off-by: Igor Druzhinin <igor.druzhinin@...rix.com>

Applied and queued up for -stable, thanks.