linux-kernel - [RFC PATCH 12/16] virtio_ring: packed: extract detach_from_vring

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Date:   Sun, 24 Apr 2022 10:40:40 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: [RFC PATCH 12/16] virtio_ring: packed: extract detach_from_vring_packed()

To handle freeing buf from the detached vring, do a split for
detach_buf_packed().

The split function detach_buf_from_vring_packed() is used to release buf
from vring, and the vq passed in is read-only. All modifications are for
vring.

In this way, detach_buf_from_vring_packed() becomes a general function,
which can be used for detach_buf_packed() and also for handling detached
vrings.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 36 +++++++++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5e6bd9a4e648..1efb47b88b40 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1703,28 +1703,28 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
 	return needs_kick;
 }
 
-static void detach_buf_packed(struct vring_virtqueue *vq,
-			      unsigned int id, void **ctx)
+static int detach_buf_from_vring_packed(struct vring_virtqueue_packed *vring,
+					struct vring_virtqueue const *vq,
+					unsigned int id,
+					unsigned int free_head,
+					void **ctx)
 {
 	struct vring_desc_state_packed *state = NULL;
 	struct vring_packed_desc *desc;
 	unsigned int i, curr;
 
-	state = &vq->packed.desc_state[id];
+	state = &vring->desc_state[id];
 
 	/* Clear data ptr. */
 	state->data = NULL;
 
-	vq->packed.desc_extra[state->last].next = vq->free_head;
-	vq->free_head = id;
-	vq->vq.num_free += state->num;
+	vring->desc_extra[state->last].next = free_head;
 
 	if (unlikely(vq->use_dma_api)) {
 		curr = id;
 		for (i = 0; i < state->num; i++) {
-			vring_unmap_extra_packed(vq,
-						 &vq->packed.desc_extra[curr]);
-			curr = vq->packed.desc_extra[curr].next;
+			vring_unmap_extra_packed(vq, &vring->desc_extra[curr]);
+			curr = vring->desc_extra[curr].next;
 		}
 	}
 
@@ -1734,10 +1734,10 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 		/* Free the indirect table, if any, now that it's unmapped. */
 		desc = state->indir_desc;
 		if (!desc)
-			return;
+			return state->num;
 
 		if (vq->use_dma_api) {
-			len = vq->packed.desc_extra[id].len;
+			len = vring->desc_extra[id].len;
 			for (i = 0; i < len / sizeof(struct vring_packed_desc);
 					i++)
 				vring_unmap_desc_packed(vq, &desc[i]);
@@ -1747,6 +1747,20 @@ static void detach_buf_packed(struct vring_virtqueue *vq,
 	} else if (ctx) {
 		*ctx = state->indir_desc;
 	}
+
+	return state->num;
+}
+
+static void detach_buf_packed(struct vring_virtqueue *vq,
+			      unsigned int id, void **ctx)
+{
+	int num;
+
+	num = detach_buf_from_vring_packed(&vq->packed, vq, id, vq->free_head,
+					   ctx);
+
+	vq->free_head = id;
+	vq->vq.num_free += num;
 }
 
 static inline bool is_used_desc_packed(const struct vring_virtqueue *vq,
-- 
2.31.0