linux-kernel - [RFC PATCH 04/16] virtio_ring: split: extract detach_from_vring

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Message-Id: <20220424024044.94749-5-xuanzhuo@linux.alibaba.com>
Date:   Sun, 24 Apr 2022 10:40:32 +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 04/16] virtio_ring: split: extract detach_from_vring_split()

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

The split function detach_buf_from_vring_split() 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_split() becomes a general function,
which can be used for detach_buf_split() and also for handling detached
vrings.

Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
---
 drivers/virtio/virtio_ring.c | 54 +++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 20 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 6fd45c9a3517..aa85058978cb 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -734,54 +734,68 @@ static bool virtqueue_kick_prepare_split(struct virtqueue *_vq)
 	return needs_kick;
 }
 
-static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
-			     void **ctx)
+static int detach_buf_from_vring_split(struct vring_virtqueue_split *vring,
+				       struct vring_virtqueue const *vq,
+				       unsigned int head,
+				       unsigned int free_head,
+				       void **ctx)
 {
-	unsigned int i, j;
+	unsigned int i, j, num = 0;
 	__virtio16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
 
 	/* Clear data ptr. */
-	vq->split.desc_state[head].data = NULL;
+	vring->desc_state[head].data = NULL;
 
 	/* Put back on free list: unmap first-level descriptors and find end */
 	i = head;
 
-	while (vq->split.vring.desc[i].flags & nextflag) {
-		vring_unmap_one_split(vq, &vq->split.desc_extra[i]);
-		i = vq->split.desc_extra[i].next;
-		vq->vq.num_free++;
+	while (vring->vring.desc[i].flags & nextflag) {
+		vring_unmap_one_split(vq, &vring->desc_extra[i]);
+		i = vring->desc_extra[i].next;
+		++num;
 	}
 
-	vring_unmap_one_split(vq, &vq->split.desc_extra[i]);
-	vq->split.desc_extra[i].next = vq->free_head;
-	vq->free_head = head;
+	vring_unmap_one_split(vq, &vring->desc_extra[i]);
+	vring->desc_extra[i].next = free_head;
 
-	/* Plus final descriptor */
-	vq->vq.num_free++;
+	++num;
 
 	if (vq->indirect) {
 		struct vring_desc *indir_desc =
-				vq->split.desc_state[head].indir_desc;
+				vring->desc_state[head].indir_desc;
 		u32 len;
 
 		/* Free the indirect table, if any, now that it's unmapped. */
 		if (!indir_desc)
-			return;
+			return num;
 
-		len = vq->split.desc_extra[head].len;
+		len = vring->desc_extra[head].len;
 
-		BUG_ON(!(vq->split.desc_extra[head].flags &
-				VRING_DESC_F_INDIRECT));
+		BUG_ON(!(vring->desc_extra[head].flags & VRING_DESC_F_INDIRECT));
 		BUG_ON(len == 0 || len % sizeof(struct vring_desc));
 
 		for (j = 0; j < len / sizeof(struct vring_desc); j++)
 			vring_unmap_one_split_indirect(vq, &indir_desc[j]);
 
 		kfree(indir_desc);
-		vq->split.desc_state[head].indir_desc = NULL;
+		vring->desc_state[head].indir_desc = NULL;
 	} else if (ctx) {
-		*ctx = vq->split.desc_state[head].indir_desc;
+		*ctx = vring->desc_state[head].indir_desc;
 	}
+
+	return num;
+}
+
+static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head,
+			     void **ctx)
+{
+	int num;
+
+	num = detach_buf_from_vring_split(&vq->split, vq, head, vq->free_head,
+					  ctx);
+
+	vq->vq.num_free += num;
+	vq->free_head = head;
 }
 
 static inline bool more_used_split(const struct vring_virtqueue *vq)
-- 
2.31.0