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Subject[PATCH 6/6] virtio-blk: Emulate Flush/FUA
Date
This patch emulates flush/fua on virtio-blk and pass xfstest on ext4.
But it needs more reviews.

Signed-off-by: Minchan Kim <minchan@redhat.com>
---
drivers/block/virtio_blk.c | 89 ++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index e32c69e..6721b9d 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -12,7 +12,6 @@
#include <linux/idr.h>

#define PART_BITS 4
-static int use_make_request = 1;

static int major;
static DEFINE_IDA(vd_index_ida);
@@ -77,6 +76,7 @@ struct virtblk_req
u8 kind;
#define VIRTIO_BLK_REQUEST 0x00
#define VIRTIO_BLK_BIO 0x01
+#define VIRTIO_BLK_BIO_FLUSH 0x02
u8 status;

struct scatterlist sg[];
@@ -160,6 +160,9 @@ static void blk_done(struct virtqueue *vq)
*/
blk_start_queue(vblk->disk->queue);
break;
+ case VIRTIO_BLK_BIO_FLUSH:
+ complete(vbr->private);
+ break;
case VIRTIO_BLK_BIO:
if (head) {
tail->next = vbr;
@@ -526,6 +529,59 @@ static void virtblk_add_buf_wait(struct virtio_blk *vblk,
finish_wait(&vblk->queue_wait, &wait);
}

+static int virtblk_flush(struct virtio_blk *vblk,
+ struct virtblk_req *vbr, struct bio *bio)
+{
+ int error;
+ bool retry, notify;
+ DECLARE_COMPLETION_ONSTACK(done);
+
+ vbr->private = &done;
+ vbr->next = NULL;
+ vbr->kind = VIRTIO_BLK_BIO_FLUSH;
+
+ vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
+ vbr->out_hdr.sector = 0;
+ if (bio)
+ vbr->out_hdr.ioprio = bio_prio(bio);
+ else
+ vbr->out_hdr.ioprio = 0;
+
+ sg_set_buf(&vbr->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
+ sg_set_buf(&vbr->sg[1], &vbr->status, sizeof(vbr->status));
+
+ spin_lock_irq(&vblk->lock);
+ if (virtqueue_add_buf(vblk->vq, vbr->sg, 1, 1, vbr) < 0) {
+ retry = true;
+ } else {
+ retry = false;
+ }
+
+ notify = virtqueue_kick_prepare(vblk->vq);
+ spin_unlock_irq(&vblk->lock);
+
+ if (notify && !virtblk_plugged(vblk))
+ virtqueue_notify(vblk->vq);
+
+ if (retry)
+ virtblk_add_buf_wait(vblk, vbr, 1, 1);
+
+ wait_for_completion(&done);
+ error = virtblk_result(vbr);
+ return error;
+}
+
+void bq_flush(struct bio_queue *bq)
+{
+ int cpu;
+ for_each_possible_cpu(cpu) {
+ struct per_cpu_bio __percpu *pcbio = per_cpu_ptr(bq->pcbio, cpu);
+ queue_work_on(cpu,
+ virtblk_wq, &pcbio->dwork.work);
+ flush_work_sync(&pcbio->dwork.work);
+ }
+}
+
bool full_segment(struct per_cpu_bio __percpu *pcbio, struct bio *bio,
unsigned int max)
{
@@ -616,9 +672,36 @@ static void virtblk_make_request(struct request_queue *q, struct bio *bio)
{
struct virtio_blk *vblk = q->queuedata;
struct per_cpu_bio __percpu *pcbio;
+ bool pre_flush, post_flush;

BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
- BUG_ON(bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+
+ pre_flush = bio->bi_rw & REQ_FLUSH;
+ post_flush = bio->bi_rw & REQ_FUA;
+
+ if (pre_flush) {
+ struct virtblk_req *dummy_vbr;
+ bq_flush(&vblk->bq);
+
+ dummy_vbr = alloc_virtblk_req(vblk, GFP_NOIO);
+ virtblk_flush(vblk, dummy_vbr, NULL);
+ mempool_free(dummy_vbr, vblk->pool);
+
+ if (bio->bi_sector && post_flush) {
+ int error;
+ struct virtblk_req *vbr;
+ vbr = alloc_virtblk_req(vblk, GFP_NOIO);
+ error = virtblk_flush(vblk, vbr, bio);
+ mempool_free(vbr, vblk->pool);
+
+ dummy_vbr = alloc_virtblk_req(vblk, GFP_NOIO);
+ virtblk_flush(vblk, dummy_vbr, NULL);
+ mempool_free(dummy_vbr, vblk->pool);
+
+ bio_endio(bio, error);
+ return;
+ }
+ }
retry:
preempt_disable();
pcbio = this_cpu_ptr(vblk->bq.pcbio);
@@ -918,7 +1001,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
vblk->index = index;

/* configure queue flush support */
- if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH) && !use_make_request)
+ if (virtio_has_feature(vdev, VIRTIO_BLK_F_FLUSH))
blk_queue_flush(q, REQ_FLUSH);

/* If disk is read-only in the host, the guest should obey */
--
1.7.6.4


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