On 10/21/24 8:43 PM, Ming Lei wrote:
> On Mon, Oct 21, 2024 at 08:03:20PM -0600, Jens Axboe wrote:
>> It's pretty pointless to use io_kiocb as intermediate storage for this,
>> so split the validity check and the actual usage. The resource node is
>> assigned upfront at prep time, to prevent it from going away. The actual
>> import is never called with the ctx->uring_lock held, so grab it for
>> the import.
>>
>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>> ---
>> io_uring/uring_cmd.c | 22 +++++++++++++++++-----
>> 1 file changed, 17 insertions(+), 5 deletions(-)
>>
>> diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
>> index 39c3c816ec78..313e2a389174 100644
>> --- a/io_uring/uring_cmd.c
>> +++ b/io_uring/uring_cmd.c
>> @@ -211,11 +211,15 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>> struct io_ring_ctx *ctx = req->ctx;
>> u16 index;
>>
>> - req->buf_index = READ_ONCE(sqe->buf_index);
>> - if (unlikely(req->buf_index >= ctx->nr_user_bufs))
>> + index = READ_ONCE(sqe->buf_index);
>> + if (unlikely(index >= ctx->nr_user_bufs))
>> return -EFAULT;
>> - index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
>> - req->imu = ctx->user_bufs[index];
>> + req->buf_index = array_index_nospec(index, ctx->nr_user_bufs);
>> + /*
>> + * Pi node upfront, prior to io_uring_cmd_import_fixed()
>> + * being called. This prevents destruction of the mapped buffer
>> + * we'll need at actual import time.
>> + */
>> io_req_set_rsrc_node(req, ctx, 0);
>> }
>> ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
>> @@ -272,8 +276,16 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
>> struct iov_iter *iter, void *ioucmd)
>> {
>> struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
>> + struct io_ring_ctx *ctx = req->ctx;
>> + struct io_mapped_ubuf *imu;
>> + int ret;
>>
>> - return io_import_fixed(rw, iter, req->imu, ubuf, len);
>> + mutex_lock(&ctx->uring_lock);
>> + imu = ctx->user_bufs[req->buf_index];
>> + ret = io_import_fixed(rw, iter, imu, ubuf, len);
>> + mutex_unlock(&ctx->uring_lock);
>
> io_uring_cmd_import_fixed is called in nvme ->issue(), and ->uring_lock
> may be held already.
Gah indeed, in fact it always should be, unless it's forcefully punted
to io-wq. I'll sort that out, thanks. And looks like we have zero tests
for uring_cmd + fixed buffers :-(
--
Jens Axboe
