linux-kernel - Re: [RESEND] [PATCH] nvme-tcp: fix usage of page_frag

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Message-ID: <e5620018-e95b-4b4e-a829-f5b3115c59e0@suse.de>
Date: Tue, 4 Nov 2025 11:40:31 +0100
From: Hannes Reinecke <hare@...e.de>
To: Dmitry Bogdanov <d.bogdanov@...ro.com>, Keith Busch <kbusch@...nel.org>,
 Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, Stuart Hayes <stuart.w.hayes@...il.com>,
 linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: linux@...ro.com, stable@...r.kernel.org
Subject: Re: [RESEND] [PATCH] nvme-tcp: fix usage of page_frag_cache

On 10/27/25 17:36, Dmitry Bogdanov wrote:
> nvme uses page_frag_cache to preallocate PDU for each preallocated request
> of block device. Block devices are created in parallel threads,
> consequently page_frag_cache is used in not thread-safe manner.
> That leads to incorrect refcounting of backstore pages and premature free.
> 
> That can be catched by !sendpage_ok inside network stack:
> 
> WARNING: CPU: 7 PID: 467 at ../net/core/skbuff.c:6931 skb_splice_from_iter+0xfa/0x310.
> 	tcp_sendmsg_locked+0x782/0xce0
> 	tcp_sendmsg+0x27/0x40
> 	sock_sendmsg+0x8b/0xa0
> 	nvme_tcp_try_send_cmd_pdu+0x149/0x2a0
> Then random panic may occur.
> 
> Fix that by serializing the usage of page_frag_cache.
> 
> Cc: stable@...r.kernel.org # 6.12
> Fixes: 4e893ca81170 ("nvme_core: scan namespaces asynchronously")
> Signed-off-by: Dmitry Bogdanov <d.bogdanov@...ro.com>
> ---
>   drivers/nvme/host/tcp.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich