Re: [RESEND] [PATCH] nvme-tcp: fix usage of page_frag_cache

[Hannes Reinecke]

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@xxxxxxxxxxxxxxx # 6.12
> Fixes: 4e893ca81170 ("nvme_core: scan namespaces asynchronously")
> Signed-off-by: Dmitry Bogdanov <d.bogdanov@xxxxxxxxx>
> ---
>   drivers/nvme/host/tcp.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
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