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FAILED: patch "[PATCH] nvme-tcp: fix usage of page_frag_cache" failed to apply to 6.6-stable tree

PATCH [email protected] 1 participant 1 message Sep 30

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The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x 36ac05f7cfd59d90c597071304b14e98090d5dd1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026093029-shadily-cattle-6976@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 36ac05f7cfd59d90c597071304b14e98090d5dd1 Mon Sep 17 00:00:00 2001
From: Dmitry Bogdanov <[email protected]>
Date: Thu, 16 Jul 2026 16:42:19 +0200
Subject: [PATCH] nvme-tcp: fix usage of page_frag_cache

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.

Fixes 4e893ca81170 ("nvme_core: scan namespaces asynchronously")
Signed-off-by Dmitry Bogdanov <[email protected]>
Signed-off-by Daniel Wagner <[email protected]>
Signed-off-by Keith Busch <[email protected]>
drivers/nvme/host/tcp.c +8 -0
index 0b2ac150b675..1d303e54e13e 100644
@@ -108,6 +108,7 @@ struct nvme_tcp_queue {
 
 	struct mutex		queue_lock;
 	struct mutex		send_mutex;
+	struct mutex		pf_cache_lock;
 	struct llist_head	req_list;
 	struct list_head	send_list;
 

@@ -552,9 +553,11 @@ static int nvme_tcp_init_request(struct blk_mq_tag_set *set,
 	struct nvme_tcp_queue *queue = &ctrl->queues[queue_idx];
 	u8 hdgst = nvme_tcp_hdgst_len(queue);
 
+	mutex_lock(&queue->pf_cache_lock);
 	req->pdu = page_frag_alloc(&queue->pf_cache,
 		sizeof(struct nvme_tcp_cmd_pdu) + hdgst,
 		GFP_KERNEL | __GFP_ZERO);
+	mutex_unlock(&queue->pf_cache_lock);
 	if (!req->pdu)
 		return -ENOMEM;
 

@@ -1419,9 +1422,11 @@ static int nvme_tcp_alloc_async_req(struct nvme_tcp_ctrl *ctrl)
 	struct nvme_tcp_request *async = &ctrl->async_req;
 	u8 hdgst = nvme_tcp_hdgst_len(queue);
 
+	mutex_lock(&queue->pf_cache_lock);
 	async->pdu = page_frag_alloc(&queue->pf_cache,
 		sizeof(struct nvme_tcp_cmd_pdu) + hdgst,
 		GFP_KERNEL | __GFP_ZERO);
+	mutex_unlock(&queue->pf_cache_lock);
 	if (!async->pdu)
 		return -ENOMEM;
 

@@ -1463,6 +1468,7 @@ static void nvme_tcp_free_queue(struct nvme_ctrl *nctrl, int qid)
 	kfree(queue->pdu);
 	mutex_destroy(&queue->send_mutex);
 	mutex_destroy(&queue->queue_lock);
+	mutex_destroy(&queue->pf_cache_lock);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	lockdep_unregister_key(&queue->nvme_tcp_sk_key);

@@ -1790,6 +1796,7 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
 	INIT_LIST_HEAD(&queue->send_list);
 	mutex_init(&queue->send_mutex);
 	INIT_WORK(&queue->io_work, nvme_tcp_io_work);
+	mutex_init(&queue->pf_cache_lock);
 
 	if (qid > 0)
 		queue->cmnd_capsule_len = nctrl->ioccsz * 16;

@@ -1930,6 +1937,7 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
 err_destroy_mutex:
 	mutex_destroy(&queue->send_mutex);
 	mutex_destroy(&queue->queue_lock);
+	mutex_destroy(&queue->pf_cache_lock);
 	return ret;
 }