From: Stefano Stabellini <sstabellini@kernel.org>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
Stefano Stabellini <stefano@aporeto.com>,
jgross@suse.com, Eric Van Hensbergen <ericvh@gmail.com>,
Ron Minnich <rminnich@sandia.gov>,
Latchesar Ionkov <lucho@ionkov.net>,
v9fs-developer@lists.sourceforge.net
Subject: Re: [PATCH 6/7] xen/9pfs: receive responses
Date: Wed, 8 Mar 2017 11:26:03 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.10.1703081125310.8160@sstabellini-ThinkPad-X260> (raw)
In-Reply-To: <b1d7aba4-0256-f02a-1b88-04d1347bc755@oracle.com>
On Wed, 8 Mar 2017, Boris Ostrovsky wrote:
> >>> +
> >>> + if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) < sizeof(h)) {
> >>> + notify_remote_via_irq(ring->irq);
> >>> + return;
> >>> + }
> >>> +
> >>> + masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
> >>> + masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
> >>> +
> >>> + xen_9pfs_read_packet(ring->ring.in,
> >>> + masked_prod, &masked_cons,
> >>> + XEN_9PFS_RING_SIZE, &h, sizeof(h));
> >>> +
> >>> + req = p9_tag_lookup(priv->client, h.tag);
> >>> + if (!req || req->status != REQ_STATUS_SENT) {
> >>> + dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
> >>> + cons += h.size;
> >>> + mb();
> >>> + ring->intf->in_cons = cons;
> >>> + continue;
> >>
> >> I don't know what xen_9pfs_read_packet() does so perhaps it's done there
> >> but shouldn't the pointers be updated regardless of the 'if' condition?
> > This is the error path - the index is increased immediately. In the
> > non-error case, we do that right after the next read_packet call, few
> > lines below.
> >
> >
> >>> + }
> >>> +
> >>> + memcpy(req->rc, &h, sizeof(h));
> >>> + req->rc->offset = 0;
> >>> +
> >>> + masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
> >>> + xen_9pfs_read_packet(ring->ring.in,
> >>> + masked_prod, &masked_cons,
> >>> + XEN_9PFS_RING_SIZE, req->rc->sdata, h.size);
> >>> +
> >>> + mb();
> >>> + cons += h.size;
> >>> + ring->intf->in_cons = cons;
> > Here ^
> >
>
>
> So the second read is reading again from the same pointer in the ring,
> but this time it gets the whole packet, including the header. The first
> read was just poking at the header. Right?
That's right. First we read the header, to know how much data to read.
> If that's correct, can you add a comment somewhere? (unless this is
> obvious to everyone else but me.)
Sure.
next prev parent reply other threads:[~2017-03-08 19:26 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-06 20:00 [PATCH 0/7] Xen transport for 9pfs frontend driver Stefano Stabellini
2017-03-06 20:01 ` [PATCH 1/7] xen: import new ring macros in ring.h Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-06 20:01 ` [PATCH 2/7] xen: introduce the header file for the Xen 9pfs transport protocol Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-06 21:22 ` Boris Ostrovsky
2017-03-06 21:22 ` Boris Ostrovsky
2017-03-06 21:36 ` Stefano Stabellini
2017-03-06 21:36 ` Stefano Stabellini
2017-03-06 21:42 ` Boris Ostrovsky
2017-03-06 21:42 ` Boris Ostrovsky
2017-03-06 20:01 ` [PATCH 3/7] xen/9pfs: introduce Xen 9pfs transport driver Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-06 20:01 ` [PATCH 4/7] xen/9pfs: connect to the backend Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-07 15:03 ` Boris Ostrovsky
2017-03-07 15:03 ` Boris Ostrovsky
2017-03-08 0:11 ` Stefano Stabellini
2017-03-08 0:11 ` Stefano Stabellini
2017-03-08 13:47 ` Boris Ostrovsky
2017-03-08 13:47 ` Boris Ostrovsky
2017-03-08 19:22 ` Stefano Stabellini
2017-03-08 19:22 ` Stefano Stabellini
2017-03-07 17:37 ` [Xen-devel] " Julien Grall
2017-03-07 17:37 ` Julien Grall
2017-03-08 0:49 ` [Xen-devel] " Stefano Stabellini
2017-03-08 0:49 ` Stefano Stabellini
2017-03-08 12:25 ` [Xen-devel] " Julien Grall
2017-03-08 12:25 ` Julien Grall
2017-03-08 19:08 ` [Xen-devel] " Stefano Stabellini
2017-03-08 19:08 ` Stefano Stabellini
2017-03-06 20:01 ` [PATCH 5/7] xen/9pfs: send requests " Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-07 15:27 ` Boris Ostrovsky
2017-03-07 15:27 ` Boris Ostrovsky
2017-03-08 0:55 ` Stefano Stabellini
2017-03-08 0:55 ` Stefano Stabellini
2017-03-08 13:58 ` Boris Ostrovsky
2017-03-08 13:58 ` Boris Ostrovsky
2017-03-08 19:33 ` Stefano Stabellini
2017-03-08 19:33 ` Stefano Stabellini
2017-03-08 20:02 ` Boris Ostrovsky
2017-03-08 20:02 ` Boris Ostrovsky
2017-03-08 20:56 ` Stefano Stabellini
2017-03-08 20:56 ` Stefano Stabellini
2017-03-08 21:01 ` Boris Ostrovsky
2017-03-08 21:01 ` Boris Ostrovsky
2017-03-06 20:01 ` [PATCH 6/7] xen/9pfs: receive responses Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-07 15:49 ` Boris Ostrovsky
2017-03-07 15:49 ` Boris Ostrovsky
2017-03-08 1:06 ` Stefano Stabellini
2017-03-08 1:06 ` Stefano Stabellini
2017-03-08 1:13 ` Stefano Stabellini
2017-03-08 1:13 ` Stefano Stabellini
2017-03-08 20:11 ` Konrad Rzeszutek Wilk
2017-03-08 20:11 ` [Xen-devel] " Konrad Rzeszutek Wilk
2017-03-08 14:33 ` Boris Ostrovsky
2017-03-08 14:33 ` Boris Ostrovsky
2017-03-08 19:26 ` Stefano Stabellini
2017-03-08 19:26 ` Stefano Stabellini [this message]
2017-03-06 20:01 ` [PATCH 7/7] xen/9pfs: build 9pfs Xen transport driver Stefano Stabellini
2017-03-06 20:01 ` Stefano Stabellini
2017-03-07 17:15 ` [Xen-devel] [PATCH 1/7] xen: import new ring macros in ring.h Julien Grall
2017-03-07 17:15 ` Julien Grall
2017-03-08 0:12 ` [Xen-devel] " Stefano Stabellini
2017-03-08 0:12 ` Stefano Stabellini
2017-03-08 11:14 ` [Xen-devel] " Julien Grall
2017-03-08 11:14 ` Julien Grall
2017-03-07 16:38 ` [Xen-devel] [PATCH 0/7] Xen transport for 9pfs frontend driver Roger Pau Monné
2017-03-07 16:38 ` Roger Pau Monné
2017-03-07 18:27 ` [Xen-devel] " Stefano Stabellini
2017-03-07 18:27 ` Stefano Stabellini
2017-03-09 3:02 ` [Xen-devel] " Roger Pau Monné
2017-03-09 3:02 ` Roger Pau Monné
2017-03-13 22:36 ` Stefano Stabellini
2017-03-13 22:36 ` [Xen-devel] " Stefano Stabellini
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