From: Keith Busch <kbusch@kernel.org>
To: Caleb Sander Mateos <csander@purestorage.com>
Cc: Keith Busch <kbusch@meta.com>,
ming.lei@redhat.com, asml.silence@gmail.com, axboe@kernel.dk,
linux-block@vger.kernel.org, io-uring@vger.kernel.org,
bernd@bsbernd.com
Subject: Re: [PATCHv3 2/5] io_uring: add support for kernel registered bvecs
Date: Tue, 18 Feb 2025 12:59:40 -0700 [thread overview]
Message-ID: <Z7TmrB4_aBnZdFbo@kbusch-mbp> (raw)
In-Reply-To: <CADUfDZpbb0mtGSRSqcepXnM9sijP6-3WAZnzUJrDGbC0AuXTrg@mail.gmail.com>
On Fri, Feb 14, 2025 at 12:38:54PM -0800, Caleb Sander Mateos wrote:
> On Fri, Feb 14, 2025 at 7:45 AM Keith Busch <kbusch@meta.com> wrote:
> > +
> > + nr_bvecs = blk_rq_nr_phys_segments(rq);
>
> Is this guaranteed to match the number of bvecs in the request?
Yes.
> Wouldn't the number of physical segments depend on how the block
> device splits the bvecs?
Also yes.
>lo_rw_aio() uses rq_for_each_bvec() to count
> the number of bvecs, for example.
Hm, that seems unnecessary. The request's nr_phys_segments is
initialized to the number of bvecs rather than page segments, so it can
be used instead of recounting them from a given struct request.
The initial number of physical segments for a request is set in
bio_split_rw_at(), which uses bio_for_each_bvec(). That's what
rq_for_each_bvec would use, too. The same is used for any bio's that get
merged into the bio.
next prev parent reply other threads:[~2025-02-18 19:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-14 15:43 [PATCHv3 0/5] ublk zero-copy support Keith Busch
2025-02-14 15:43 ` [PATCHv3 1/5] io_uring: move fixed buffer import to issue path Keith Busch
2025-02-18 20:32 ` Caleb Sander Mateos
2025-02-14 15:43 ` [PATCHv3 2/5] io_uring: add support for kernel registered bvecs Keith Busch
2025-02-14 20:38 ` Caleb Sander Mateos
2025-02-18 19:59 ` Keith Busch [this message]
2025-02-18 20:20 ` Caleb Sander Mateos
2025-02-14 15:43 ` [PATCHv3 3/5] ublk: zc register/unregister bvec Keith Busch
2025-02-14 15:43 ` [PATCHv3 4/5] io_uring: add abstraction for buf_table rsrc data Keith Busch
2025-02-14 15:43 ` [PATCHv3 5/5] io_uring: cache nodes and mapped buffers Keith Busch
2025-02-15 2:22 ` Caleb Sander Mateos
2025-02-16 22:43 ` Caleb Sander Mateos
2025-02-18 20:12 ` Keith Busch
2025-02-18 20:45 ` Caleb Sander Mateos
2025-02-18 20:09 ` Keith Busch
2025-02-18 20:42 ` Caleb Sander Mateos
2025-02-18 21:12 ` Keith Busch
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