Re: [RFC blktests fix PATCH] tcp: use GFP_ATOMIC in tcp_disconnect
From: Nilay Shroff <hidden>
Date: 2025-11-25 11:14:26
Also in:
linux-block, linux-nvme
On 11/25/25 12:58 PM, Chaitanya Kulkarni wrote:
quoted hunk ↗ jump to hunk
On 11/24/25 22:27, Christoph Hellwig wrote:quoted
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);
The memalloc_noreclaim_save() above shall already prevent filesystem reclaim, so if the goal is to avoid fs_reclaim, we should not need an additional memalloc_noio_save() here. That makes me wonder whether we are looking at the correct code path. If this teardown path (nvme_tcp_free_queue()) is indeed executed, it should already be avoiding filesystem reclaim in the first place. Thanks, --Nilay