From: Christoph Hellwig <hch@lst.de>
To: Chao Shi <coshi036@gmail.com>
Cc: Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Chaitanya Kulkarni <kch@nvidia.com>,
linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
Sungwoo Kim <iam@sung-woo.kim>, Dave Tian <daveti@purdue.edu>,
Weidong Zhu <weizhu@fiu.edu>
Subject: Re: [PATCH] nvme: bound the freeze drain in passthrough commands
Date: Wed, 27 May 2026 15:26:59 +0200 [thread overview]
Message-ID: <20260527132658.GA11713@lst.de> (raw)
In-Reply-To: <20260527055923.456769-1-coshi036@gmail.com>
On Wed, May 27, 2026 at 01:59:23AM -0400, Chao Shi wrote:
> nvme_passthru_start() drains in-flight I/O via the unbounded
> nvme_wait_freeze() before submitting a command with command-set
> effects (Format NVM, Sanitize, Namespace Management, vendor unique).
> If a completion is silently dropped or the device hangs, the calling
> task wedges with ctrl->scan_lock and ctrl->subsys->lock held, fanning
> out into hung-task reports on any concurrent open/close/passthru on
> the same controller:
>
> INFO: task syz-executor:NNNN blocked for more than 123 seconds.
> nvme_wait_freeze+0x82/0x100
> nvme_passthru_start drivers/nvme/host/core.c:1249 [inline]
> nvme_submit_user_cmd+0x1ee/0x3d0 drivers/nvme/host/ioctl.c:189
>
> The other freeze-drain sites (pci shutdown, tcp/rdma reset) already
> bound the wait with nvme_wait_freeze_timeout(NVME_IO_TIMEOUT). Apply
> it here too; on timeout, unwind the freeze and return -EBUSY (or
> NVME_SC_INTERNAL on the nvmet path) instead of submitting the command.
>
> Found by FuzzNvme(Syzkaller with FEMU fuzzing framework).
So not blocking forever sounds useful, but this might break existing
uses. I guess we could do it based on the O_NONBLOCK flag if people
really cared.
Note that the blocked message itself is not a problem, but around
this time we should have done a controller reset and fixed up the
issue. Does that not happen for your test case?
next prev parent reply other threads:[~2026-05-27 13:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-27 5:59 [PATCH] nvme: bound the freeze drain in passthrough commands Chao Shi
2026-05-27 13:26 ` Christoph Hellwig [this message]
2026-05-27 15:46 ` Keith Busch
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