This patch is a fix specific to the 3.19 - 4.4 kernels. The 4.5 kernel inadvertently fixed this bug differently (db3cbfff5bcc0), but is not a stable candidate due it being a complicated re-write of the entire feature.
This patch fixes a potential timing bug with nvme's asynchronous queue deletion, which causes an allocated request to be accidentally released due to the ordering of the shared completion context among the sq/cq pair. The completion context saves the request that issued the queue deletion. If the submission side deletion happens to reset the active request, the completion side will release the wrong request tag back into the pool of available tags. This means the driver will create multiple commands with the same tag, corrupting the queue context.
The error is observable in the kernel logs like:
"nvme XX:YY:ZZ completed id XX twice on qid:0"
In this particular case, this message occurs because the queue is corrupted.
The following timing sequence demonstrates the error:
CPU A CPU B ----------------------- ----------------------------- nvme_irq nvme_process_cq async_completion queue_kthread_work -----------> nvme_del_sq_work_handler nvme_delete_cq adapter_async_del_queue nvme_submit_admin_async_cmd cmdinfo->req = req;
blk_mq_free_request(cmdinfo->req); <-- wrong request!!!
This patch fixes the bug by releasing the request in the completion side prior to waking the submission thread, such that that thread can't muck with the shared completion context.
Fixes: a4aea5623d4a5 ("NVMe: Convert to blk-mq")
Cc: stable@vger.kernel.org # 4.4.x Cc: stable@vger.kernel.org # 4.1.x Signed-off-by: Keith Busch keith.busch@intel.com --- drivers/nvme/host/pci.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index 669edbd47602..d6ceb8b91cd6 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -350,8 +350,8 @@ static void async_completion(struct nvme_queue *nvmeq, void *ctx, struct async_cmd_info *cmdinfo = ctx; cmdinfo->result = le32_to_cpup(&cqe->result); cmdinfo->status = le16_to_cpup(&cqe->status) >> 1; - queue_kthread_work(cmdinfo->worker, &cmdinfo->work); blk_mq_free_request(cmdinfo->req); + queue_kthread_work(cmdinfo->worker, &cmdinfo->work); }
static inline struct nvme_cmd_info *get_cmd_from_tag(struct nvme_queue *nvmeq,