netdev - Re: [RFC blktests fix PATCH] tcp: use GFP_ATOMIC in tcp

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Message-ID: <ea2958c9-4571-4169-8060-6456892e6b15@nvidia.com>
Date: Tue, 25 Nov 2025 07:28:45 +0000
From: Chaitanya Kulkarni <chaitanyak@...dia.com>
To: Christoph Hellwig <hch@...radead.org>, Chaitanya Kulkarni
	<ckulkarnilinux@...il.com>
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Subject: Re: [RFC blktests fix PATCH] tcp: use GFP_ATOMIC in tcp_disconnect

On 11/24/25 22:27, Christoph Hellwig wrote:
> I don't think GFP_ATOMIC is right here, you want GFP_NOIO.
>
> And just use the scope API so that you don't have to pass a gfp_t
> several layers down.
>
>
are you saying something like this ?

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 29ad4735fac6..56d0a3777a4d 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1438,17 +1438,28 @@ static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
  	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
  	struct nvme_tcp_queue *queue = &ctrl->queues[qid];
  	unsigned int noreclaim_flag;
+	unsigned int noio_flag;
  
  	if (!test_and_clear_bit(NVME_TCP_Q_ALLOCATED, &queue->flags))
  		return;
  
  	page_frag_cache_drain(&queue->pf_cache);
  
+	/**
+	 * Prevent memory reclaim from triggering block I/O during socket
+	 * teardown. The socket release path fput -> tcp_close ->
+	 * tcp_disconnect -> tcp_send_active_reset may allocate memory, and
+	 * allowing reclaim to issue I/O could deadlock if we're being called
+	 * from block device teardown (e.g., del_gendisk -> elevator cleanup)
+	 * which holds locks that the I/O completion path needs.
+	 */
+	noio_flag = memalloc_noio_save();
  	noreclaim_flag = memalloc_noreclaim_save();
  	/* ->sock will be released by fput() */
  	fput(queue->sock->file);
  	queue->sock = NULL;
  	memalloc_noreclaim_restore(noreclaim_flag);
+	memalloc_noio_restore(noio_flag);
  
  	kfree(queue->pdu);
  	mutex_destroy(&queue->send_mutex);
-- 
2.40.0

-ck