We need to support both REQ_FLUSH and REQ_FUA for bio based path since
it does not get the sequencing of REQ_FUA into REQ_FLUSH that request
based drivers can request.
REQ_FLUSH is emulated by:
1. Send VIRTIO_BLK_T_FLUSH to device
2. Wait until the flush is finished
REQ_FUA is emulated by:
1. Send the actual write
2. Wait until the actual write is finished
3. Send VIRTIO_BLK_T_FLUSH to device
4. Wait until the flush is finished
5. Signal the end of the write to upper layer
Cc: Rusty Russell <ru...@rustcorp.com.au>
Cc: Jens Axboe <ax...@kernel.dk>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Tejun Heo <t...@kernel.org>
Cc: Shaohua Li <s...@kernel.org>
Cc: "Michael S. Tsirkin" <m...@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-ker...@vger.kernel.org
Cc: virtualizat...@lists.linux-foundation.org
Signed-off-by: Asias He <as...@redhat.com>
---
drivers/block/virtio_blk.c | 104 +++++++++++++++++++++++++++++++++++++++------
1 file changed, 91 insertions(+), 13 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 95cfeed..9ebaea7 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -54,6 +54,8 @@ struct virtio_blk
struct virtblk_req
{
+ struct completion *flush_done;
+ struct completion *bio_done;
struct request *req;
struct bio *bio;
struct virtio_blk_outhdr out_hdr;
@@ -95,14 +97,25 @@ static inline void virtblk_request_done(struct virtio_blk
*vblk,
static inline void virtblk_bio_done(struct virtio_blk *vblk,
struct virtblk_req *vbr)
{
+ if (unlikely(vbr->bio_done)) {
+ complete(vbr->bio_done);
+ return;
+ }
bio_endio(vbr->bio, virtblk_result(vbr));
mempool_free(vbr, vblk->pool);
}
+static inline void virtblk_flush_done(struct virtio_blk *vblk,
+ struct virtblk_req *vbr)
+{
+ complete(vbr->flush_done);
+ mempool_free(vbr, vblk->pool);
+}
+
static void virtblk_done(struct virtqueue *vq)
{
+ unsigned long flush_done = 0, bio_done = 0, req_done = 0;
struct virtio_blk *vblk = vq->vdev->priv;
- unsigned long bio_done = 0, req_done = 0;
struct virtblk_req *vbr;
unsigned long flags;
unsigned int len;
@@ -112,9 +125,12 @@ static void virtblk_done(struct virtqueue *vq)
if (vbr->bio) {
virtblk_bio_done(vblk, vbr);
bio_done++;
- } else {
+ } else if (vbr->req) {
virtblk_request_done(vblk, vbr);
req_done++;
+ } else if (vbr->flush_done) {
+ virtblk_flush_done(vblk, vbr);
+ flush_done++;
}
}
/* In case queue is stopped waiting for more buffers. */
@@ -122,7 +138,7 @@ static void virtblk_done(struct virtqueue *vq)
blk_start_queue(vblk->disk->queue);
spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags);
- if (bio_done)
+ if (bio_done || flush_done)
wake_up(&vblk->queue_wait);
}
@@ -269,14 +285,65 @@ static void virtblk_add_buf_wait(struct virtio_blk *vblk,
finish_wait(&vblk->queue_wait, &wait);
}
+static inline void virtblk_add_req(struct virtio_blk *vblk,
+ struct virtblk_req *vbr,
+ unsigned int out, unsigned int in)
+{
+ spin_lock_irq(vblk->disk->queue->queue_lock);
+ if (unlikely(virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
+ GFP_ATOMIC) < 0)) {
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+ virtblk_add_buf_wait(vblk, vbr, out, in);
+ return;
+ }
+ virtqueue_kick(vblk->vq);
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+}
+
+static int virtblk_flush(struct virtio_blk *vblk)
+{
+ DECLARE_COMPLETION_ONSTACK(done);
+ unsigned int out = 0, in = 0;
+ struct virtblk_req *vbr;
+
+ vbr = virtblk_alloc_req(vblk, GFP_NOIO);
+ if (!vbr)
+ return -ENOMEM;
+
+ vbr->flush_done = &done;
+ vbr->bio = NULL;
+ vbr->req = NULL;
+ vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
+ vbr->out_hdr.sector = 0;
+ vbr->out_hdr.ioprio = 0;
+ sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
+ sg_set_buf(&vbr->sg[out + in++], &vbr->status, sizeof(vbr->status));
+
+ virtblk_add_req(vblk, vbr, out, in);
+
+ wait_for_completion(&done);
+
+ return 0;
+}
+
static void virtblk_make_request(struct request_queue *q, struct bio *bio)
{
+ bool req_flush = false, req_fua = false;
struct virtio_blk *vblk = q->queuedata;
unsigned int num, out = 0, in = 0;
+ DECLARE_COMPLETION_ONSTACK(done);
struct virtblk_req *vbr;
BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
- BUG_ON(bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+
+ if (bio->bi_rw & REQ_FLUSH)
+ req_flush = true;
+ if (bio->bi_rw & REQ_FUA)
+ req_fua = true;
+
+ /* Execute a flush & wait until it finishes */
+ if (unlikely(req_flush))
+ virtblk_flush(vblk);
vbr = virtblk_alloc_req(vblk, GFP_NOIO);
if (!vbr) {
@@ -290,6 +357,11 @@ static void virtblk_make_request(struct request_queue *q,
struct bio *bio)
vbr->out_hdr.sector = bio->bi_sector;
vbr->out_hdr.ioprio = bio_prio(bio);
+ if (unlikely(req_fua))
+ vbr->bio_done = &done;
+ else
+ vbr->bio_done = NULL;
+
sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
num = blk_bio_map_sg(q, bio, vbr->sg + out);
@@ -307,15 +379,21 @@ static void virtblk_make_request(struct request_queue *q,
struct bio *bio)
}
}
- spin_lock_irq(vblk->disk->queue->queue_lock);
- if (unlikely(virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
- GFP_ATOMIC) < 0)) {
- spin_unlock_irq(vblk->disk->queue->queue_lock);
- virtblk_add_buf_wait(vblk, vbr, out, in);
- return;
+ virtblk_add_req(vblk, vbr, out, in);
+
+ if (unlikely(req_fua)) {
+ /*
+ * We emulate the REQ_FUA here:
+ *
+ * 1. Wait until the bio is finished
+ * 2. Execute a flush & wait until it finishes
+ * 3. Signal the end of the bio & free the vbr
+ */
+ wait_for_completion(vbr->bio_done);
+ virtblk_flush(vblk);
+ bio_endio(vbr->bio, virtblk_result(vbr));
+ mempool_free(vbr, vblk->pool);
}
- virtqueue_kick(vblk->vq);
- spin_unlock_irq(vblk->disk->queue->queue_lock);
}
/* return id (s/n) string for *disk to *id_str
@@ -529,7 +607,7 @@ static void virtblk_update_cache_mode(struct virtio_device
*vdev)
u8 writeback = virtblk_get_cache_mode(vdev);
struct virtio_blk *vblk = vdev->priv;
- if (writeback && !use_bio)
+ if (writeback)
blk_queue_flush(vblk->disk->queue, REQ_FLUSH);
else
blk_queue_flush(vblk->disk->queue, 0);
--
1.7.11.2
--
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