From: Christoph Hellwig <[email protected]>
To: Kanchan Joshi <[email protected]>
Cc: [email protected], [email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected], Anuj Gupta <[email protected]>
Subject: Re: [PATCH for-next v7 4/5] block: add helper to map bvec iterator for passthrough
Date: Tue, 20 Sep 2022 14:08:02 +0200 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
> -static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> +static struct bio *bio_map_get(struct request *rq, unsigned int nr_vecs,
> gfp_t gfp_mask)
bio_map_get is a very confusing name. And I also still think this is
the wrong way to go. If plain slab allocations don't use proper
per-cpu caches we have a MM problem and need to talk to the slab
maintainers and not use the overkill bio_set here.
> +/* Prepare bio for passthrough IO given an existing bvec iter */
> +int blk_rq_map_user_bvec(struct request *rq, struct iov_iter *iter)
I'm a little confused about the interface we're trying to present from
the block layer to the driver here.
blk_rq_map_user_iov really should be able to detect that it is called
on a bvec iter and just do the right thing rather than needing different
helpers.
> + /*
> + * If the queue doesn't support SG gaps and adding this
> + * offset would create a gap, disallow it.
> + */
> + if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv->bv_offset))
> + goto out_err;
So now you limit the input that is accepted? That's not really how
iov_iters are used. We can either try to reshuffle the bvecs, or
just fall back to the copy data version as blk_rq_map_user_iov does
for 'weird' iters˙
> +
> + /* check full condition */
> + if (nsegs >= nr_segs || bytes > UINT_MAX - bv->bv_len)
> + goto out_err;
> +
> + if (bytes + bv->bv_len <= nr_iter &&
> + bv->bv_offset + bv->bv_len <= PAGE_SIZE) {
> + nsegs++;
> + bytes += bv->bv_len;
> + } else
> + goto out_err;
Nit: This would read much better as:
if (bytes + bv->bv_len > nr_iter)
goto out_err;
if (bv->bv_offset + bv->bv_len > PAGE_SIZE)
goto out_err;
bytes += bv->bv_len;
nsegs++;
next prev parent reply other threads:[~2022-09-20 12:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20220909103131epcas5p23d146916eccedf30d498e0ea23e54052@epcas5p2.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 0/5] fixed-buffer for uring-cmd/passthru Kanchan Joshi
[not found] ` <CGME20220909103136epcas5p38ea3a933e90d9f9d7451848dc3a60829@epcas5p3.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 1/5] io_uring: add io_uring_cmd_import_fixed Kanchan Joshi
[not found] ` <CGME20220909103140epcas5p36689726422eb68e6fdc1d39019a4a8ba@epcas5p3.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 2/5] io_uring: introduce fixed buffer support for io_uring_cmd Kanchan Joshi
[not found] ` <CGME20220909103143epcas5p2eda60190cd23b79fb8f48596af3e1524@epcas5p2.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 3/5] nvme: refactor nvme_alloc_user_request Kanchan Joshi
2022-09-20 12:02 ` Christoph Hellwig
2022-09-22 15:46 ` Kanchan Joshi
2022-09-23 9:25 ` Kanchan Joshi
[not found] ` <CGME20220909103147epcas5p2a83ec151333bcb1d2abb8c7536789bfd@epcas5p2.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 4/5] block: add helper to map bvec iterator for passthrough Kanchan Joshi
2022-09-20 12:08 ` Christoph Hellwig [this message]
2022-09-22 15:23 ` Kanchan Joshi
2022-09-23 15:29 ` Christoph Hellwig
2022-09-23 18:43 ` Kanchan Joshi
2022-09-25 17:46 ` Kanchan Joshi
2022-09-26 14:50 ` Christoph Hellwig
2022-09-27 16:47 ` Kanchan Joshi
[not found] ` <CGME20220909103151epcas5p1e25127c3053ba21e8f8418a701878973@epcas5p1.samsung.com>
2022-09-09 10:21 ` [PATCH for-next v7 5/5] nvme: wire up fixed buffer support for nvme passthrough Kanchan Joshi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox