From: Kanchan Joshi <joshi.k@samsung.com>
To: Caleb Sander Mateos <csander@purestorage.com>,
Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
Pavel Begunkov <asml.silence@gmail.com>
Cc: Chaitanya Kulkarni <kch@nvidia.com>,
linux-nvme@lists.infradead.org, io-uring@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 3/3] nvme/ioctl: move fixed buffer lookup to nvme_uring_cmd_io()
Date: Mon, 31 Mar 2025 12:16:58 +0530 [thread overview]
Message-ID: <48b9a876-0e3b-4c89-9aa3-b48f502868c3@samsung.com> (raw)
In-Reply-To: <20250328154647.2590171-4-csander@purestorage.com>
On 3/28/2025 9:16 PM, Caleb Sander Mateos wrote:
> For NVMe passthru operations with fixed buffers, the fixed buffer lookup
> happens in io_uring_cmd_import_fixed(). But nvme_uring_cmd_io() can
> return -EAGAIN first from nvme_alloc_user_request() if all tags in the
> tag set are in use. This ordering difference is observable when using
> UBLK_U_IO_{,UN}REGISTER_IO_BUF SQEs to modify the fixed buffer table. If
> the NVMe passthru operation is followed by UBLK_U_IO_UNREGISTER_IO_BUF
> to unregister the fixed buffer and the NVMe passthru goes async, the
> fixed buffer lookup will fail because it happens after the unregister.
while the patch looks fine, I wonder what setup is required to
trigger/test this. Given that io_uring NVMe passthru is on the char
device node, and ublk does not take char device as the backing file.
Care to explain?
next prev parent reply other threads:[~2025-03-31 6:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-28 15:46 [PATCH v4 0/3] nvme_map_user_request() cleanup Caleb Sander Mateos
2025-03-28 15:46 ` [PATCH v4 1/3] nvme/ioctl: don't warn on vectorized uring_cmd with fixed buffer Caleb Sander Mateos
2025-03-28 15:46 ` [PATCH v4 2/3] nvme/ioctl: move blk_mq_free_request() out of nvme_map_user_request() Caleb Sander Mateos
2025-03-28 15:46 ` [PATCH v4 3/3] nvme/ioctl: move fixed buffer lookup to nvme_uring_cmd_io() Caleb Sander Mateos
2025-03-31 6:46 ` Kanchan Joshi [this message]
2025-03-31 14:36 ` Keith Busch
2025-04-02 13:21 ` Kanchan Joshi
2025-03-28 17:31 ` [PATCH v4 0/3] nvme_map_user_request() cleanup Keith Busch
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