Re: [PATCH for-next v8 3/5] nvme: refactor nvme_alloc_user_request

Kanchan Joshi
2022-09-25T17:50:04Z

[-- Attachment #1: Type: text/plain, Size: 1324 bytes --]

On Fri, Sep 23, 2022 at 05:38:19PM +0200, Christoph Hellwig wrote:
>
>> + else {
>> + struct iovec fast_iov[UIO_FASTIOV];
>> + struct iovec *iov = fast_iov;
>> + struct iov_iter iter;
>> +
>> + ret = import_iovec(rq_data_dir(req), ubuffer, bufflen,
>> + UIO_FASTIOV, &iov, &iter);
>> + if (ret < 0)
>> goto out;
>> + ret = blk_rq_map_user_iov(q, req, NULL, &iter, GFP_KERNEL);
>> + kfree(iov);
>> + }
>
>While you touch this: I think thi block of code would also be a good
>separate helper. Maybe even in the block layer given the the scsi
>ioctl code and sg duplicate it, and already missed the fast_iov
>treatment due to the duplication. Having this in a separate function
>is also nice to keep the fast_iov stack footprint isolated.

Totally agree on goodness.
I think instead of new helper this seems suited to go inside
blk_rq_map_user_iov itself. That will make it symmetric to
blk_rq_map_user which also combines import + mapping.

But if I go that route now, I will have to alter parameters of
blk_rq_map_user_iov, and that will make it mandatory to change the
callers (scsi-ioctl, sg) too. Nothing hairy, but that means further
growth of unrelated elements in this series. Hope you agree that
separate series is much better, which I will post after this.

Will fold all other changes you pointed.

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]