Hi, all
Changes in v7:
- Using vbr->flags to trace request type
- Dropped unnecessary struct virtio_blk *vblk parameter
- Reuse struct virtblk_req in bio done function
- Added performance data on normal SATA device and the reason why make it optional
Fio test shows bio-based IO path gives the following performance improvement:
1) Ramdisk device
With bio-based IO path, sequential read/write, random read/write
IOPS boost : 28%, 24%, 21%, 16%
Latency improvement: 32%, 17%, 21%, 16%
2) Fusion IO device
With bio-based IO path, sequential read/write, random read/write
IOPS boost : 11%, 11%, 13%, 10%
Latency improvement: 10%, 10%, 12%, 10%
3) Normal SATA device
With bio-based IO path, sequential read/write, random read/write
IOPS boost : -10%, -10%, 4.4%, 0.5%
Latency improvement: -12%, -15%, 2.5%, 0.8%
Asias He (2):
virtio-blk: Add bio-based IO path for virtio-blk
virtio-blk: Add REQ_FLUSH and REQ_FUA support to bio path
drivers/block/virtio_blk.c | 301 +++++++++++++++++++++++++++++++++++++++------
1 file changed, 264 insertions(+), 37 deletions(-)
--
1.7.11.2
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:
A) If the bio has no data to write:
1. Send VIRTIO_BLK_T_FLUSH to device,
2. In the flush I/O completion handler, finish the bio
B) If the bio has data to write:
1. Send VIRTIO_BLK_T_FLUSH to device
2. In the flush I/O completion handler, send the actual write data to device
3. In the write I/O completion handler, finish the bio
REQ_FUA is emulated by:
1. Send the actual write data to device
2. In the write I/O completion handler, send VIRTIO_BLK_T_FLUSH to device
3. In the flush I/O completion handler, finish the bio
Changes in v7:
- Using vbr->flags to trace request type
- Dropped unnecessary struct virtio_blk *vblk parameter
- Reuse struct virtblk_req in bio done function
Cahnges in v6:
- Reworked REQ_FLUSH and REQ_FUA emulatation order
Cc: Rusty Russell <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Asias He <[email protected]>
---
drivers/block/virtio_blk.c | 272 +++++++++++++++++++++++++++++++--------------
1 file changed, 188 insertions(+), 84 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 95cfeed..2edfb5c 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -58,10 +58,20 @@ struct virtblk_req
struct bio *bio;
struct virtio_blk_outhdr out_hdr;
struct virtio_scsi_inhdr in_hdr;
+ struct work_struct work;
+ struct virtio_blk *vblk;
+ int flags;
u8 status;
struct scatterlist sg[];
};
+enum {
+ VBLK_IS_FLUSH = 1,
+ VBLK_REQ_FLUSH = 2,
+ VBLK_REQ_DATA = 4,
+ VBLK_REQ_FUA = 8,
+};
+
static inline int virtblk_result(struct virtblk_req *vbr)
{
switch (vbr->status) {
@@ -74,9 +84,133 @@ static inline int virtblk_result(struct virtblk_req *vbr)
}
}
-static inline void virtblk_request_done(struct virtio_blk *vblk,
- struct virtblk_req *vbr)
+static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
+ gfp_t gfp_mask)
+{
+ struct virtblk_req *vbr;
+
+ vbr = mempool_alloc(vblk->pool, gfp_mask);
+ if (vbr && use_bio)
+ sg_init_table(vbr->sg, vblk->sg_elems);
+
+ vbr->vblk = vblk;
+
+ return vbr;
+}
+
+static void virtblk_add_buf_wait(struct virtio_blk *vblk,
+ struct virtblk_req *vbr,
+ unsigned long out,
+ unsigned long in)
+{
+ DEFINE_WAIT(wait);
+
+ for (;;) {
+ prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ spin_lock_irq(vblk->disk->queue->queue_lock);
+ if (virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
+ GFP_ATOMIC) < 0) {
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+ io_schedule();
+ } else {
+ virtqueue_kick(vblk->vq);
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+ break;
+ }
+
+ }
+
+ finish_wait(&vblk->queue_wait, &wait);
+}
+
+static inline void virtblk_add_req(struct virtblk_req *vbr,
+ unsigned int out, unsigned int in)
+{
+ struct virtio_blk *vblk = vbr->vblk;
+
+ 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_bio_send_flush(struct virtblk_req *vbr)
+{
+ unsigned int out = 0, in = 0;
+
+ vbr->flags |= VBLK_IS_FLUSH;
+ 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(vbr, out, in);
+
+ return 0;
+}
+
+static int virtblk_bio_send_data(struct virtblk_req *vbr)
{
+ struct virtio_blk *vblk = vbr->vblk;
+ unsigned int num, out = 0, in = 0;
+ struct bio *bio = vbr->bio;
+
+ vbr->flags &= ~VBLK_IS_FLUSH;
+ vbr->out_hdr.type = 0;
+ vbr->out_hdr.sector = bio->bi_sector;
+ vbr->out_hdr.ioprio = bio_prio(bio);
+
+ sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
+
+ num = blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg + out);
+
+ sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
+ sizeof(vbr->status));
+
+ if (num) {
+ if (bio->bi_rw & REQ_WRITE) {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+ out += num;
+ } else {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+ in += num;
+ }
+ }
+
+ virtblk_add_req(vbr, out, in);
+
+ return 0;
+}
+
+static void virtblk_bio_send_data_work(struct work_struct *work)
+{
+ struct virtblk_req *vbr;
+
+ vbr = container_of(work, struct virtblk_req, work);
+
+ virtblk_bio_send_data(vbr);
+}
+
+static void virtblk_bio_send_flush_work(struct work_struct *work)
+{
+ struct virtblk_req *vbr;
+
+ vbr = container_of(work, struct virtblk_req, work);
+
+ virtblk_bio_send_flush(vbr);
+}
+
+static inline void virtblk_request_done(struct virtblk_req *vbr)
+{
+ struct virtio_blk *vblk = vbr->vblk;
struct request *req = vbr->req;
int error = virtblk_result(vbr);
@@ -92,17 +226,47 @@ static inline void virtblk_request_done(struct virtio_blk *vblk,
mempool_free(vbr, vblk->pool);
}
-static inline void virtblk_bio_done(struct virtio_blk *vblk,
- struct virtblk_req *vbr)
+static inline void virtblk_bio_flush_done(struct virtblk_req *vbr)
{
- bio_endio(vbr->bio, virtblk_result(vbr));
- mempool_free(vbr, vblk->pool);
+ struct virtio_blk *vblk = vbr->vblk;
+
+ if (vbr->flags & VBLK_REQ_DATA) {
+ /* Send out the actual write data */
+ INIT_WORK(&vbr->work, virtblk_bio_send_data_work);
+ queue_work(virtblk_wq, &vbr->work);
+ } else {
+ bio_endio(vbr->bio, virtblk_result(vbr));
+ mempool_free(vbr, vblk->pool);
+ }
+}
+
+static inline void virtblk_bio_data_done(struct virtblk_req *vbr)
+{
+ struct virtio_blk *vblk = vbr->vblk;
+
+ if (unlikely(vbr->flags & VBLK_REQ_FUA)) {
+ /* Send out a flush before end the bio */
+ vbr->flags &= ~VBLK_REQ_DATA;
+ INIT_WORK(&vbr->work, virtblk_bio_send_flush_work);
+ queue_work(virtblk_wq, &vbr->work);
+ } else {
+ bio_endio(vbr->bio, virtblk_result(vbr));
+ mempool_free(vbr, vblk->pool);
+ }
+}
+
+static inline void virtblk_bio_done(struct virtblk_req *vbr)
+{
+ if (unlikely(vbr->flags & VBLK_IS_FLUSH))
+ virtblk_bio_flush_done(vbr);
+ else
+ virtblk_bio_data_done(vbr);
}
static void virtblk_done(struct virtqueue *vq)
{
struct virtio_blk *vblk = vq->vdev->priv;
- unsigned long bio_done = 0, req_done = 0;
+ bool bio_done = false, req_done = false;
struct virtblk_req *vbr;
unsigned long flags;
unsigned int len;
@@ -110,11 +274,11 @@ static void virtblk_done(struct virtqueue *vq)
spin_lock_irqsave(vblk->disk->queue->queue_lock, flags);
while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
if (vbr->bio) {
- virtblk_bio_done(vblk, vbr);
- bio_done++;
+ virtblk_bio_done(vbr);
+ bio_done = true;
} else {
- virtblk_request_done(vblk, vbr);
- req_done++;
+ virtblk_request_done(vbr);
+ req_done = true;
}
}
/* In case queue is stopped waiting for more buffers. */
@@ -126,18 +290,6 @@ static void virtblk_done(struct virtqueue *vq)
wake_up(&vblk->queue_wait);
}
-static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
- gfp_t gfp_mask)
-{
- struct virtblk_req *vbr;
-
- vbr = mempool_alloc(vblk->pool, gfp_mask);
- if (vbr && use_bio)
- sg_init_table(vbr->sg, vblk->sg_elems);
-
- return vbr;
-}
-
static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
struct request *req)
{
@@ -242,41 +394,12 @@ static void virtblk_request(struct request_queue *q)
virtqueue_kick(vblk->vq);
}
-static void virtblk_add_buf_wait(struct virtio_blk *vblk,
- struct virtblk_req *vbr,
- unsigned long out,
- unsigned long in)
-{
- DEFINE_WAIT(wait);
-
- for (;;) {
- prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
- TASK_UNINTERRUPTIBLE);
-
- spin_lock_irq(vblk->disk->queue->queue_lock);
- if (virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
- GFP_ATOMIC) < 0) {
- spin_unlock_irq(vblk->disk->queue->queue_lock);
- io_schedule();
- } else {
- virtqueue_kick(vblk->vq);
- spin_unlock_irq(vblk->disk->queue->queue_lock);
- break;
- }
-
- }
-
- finish_wait(&vblk->queue_wait, &wait);
-}
-
static void virtblk_make_request(struct request_queue *q, struct bio *bio)
{
struct virtio_blk *vblk = q->queuedata;
- unsigned int num, out = 0, in = 0;
struct virtblk_req *vbr;
BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
- BUG_ON(bio->bi_rw & (REQ_FLUSH | REQ_FUA));
vbr = virtblk_alloc_req(vblk, GFP_NOIO);
if (!vbr) {
@@ -285,37 +408,18 @@ static void virtblk_make_request(struct request_queue *q, struct bio *bio)
}
vbr->bio = bio;
- vbr->req = NULL;
- vbr->out_hdr.type = 0;
- vbr->out_hdr.sector = bio->bi_sector;
- vbr->out_hdr.ioprio = bio_prio(bio);
-
- sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
-
- num = blk_bio_map_sg(q, bio, vbr->sg + out);
-
- sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
- sizeof(vbr->status));
-
- if (num) {
- if (bio->bi_rw & REQ_WRITE) {
- vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
- out += num;
- } else {
- vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
- in += num;
- }
- }
-
- 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);
+ vbr->flags = 0;
+ if (bio->bi_rw & REQ_FLUSH)
+ vbr->flags |= VBLK_REQ_FLUSH;
+ if (bio->bi_rw & REQ_FUA)
+ vbr->flags |= VBLK_REQ_FUA;
+ if (bio->bi_size)
+ vbr->flags |= VBLK_REQ_DATA;
+
+ if (unlikely(vbr->flags & VBLK_REQ_FLUSH))
+ virtblk_bio_send_flush(vbr);
+ else
+ virtblk_bio_send_data(vbr);
}
/* return id (s/n) string for *disk to *id_str
@@ -529,7 +633,7 @@ 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
This patch introduces bio-based IO path for virtio-blk.
Compared to request-based IO path, bio-based IO path uses driver
provided ->make_request_fn() method to bypasses the IO scheduler. It
handles the bio to device directly without allocating a request in block
layer. This reduces the IO path in guest kernel to achieve high IOPS
and lower latency. The downside is that guest can not use the IO
scheduler to merge and sort requests. However, this is not a big problem
if the backend disk in host side uses faster disk device.
When the bio-based IO path is not enabled, virtio-blk still uses the
original request-based IO path, no performance difference is observed.
Using a slow device e.g. normal SATA disk, the bio-based IO path for
sequential read and write are slower than req-based IO path due to lack
of merge in guest kernel. So we make the bio-based path optional.
Performance evaluation:
-----------------------------
1) Fio test is performed in a 8 vcpu guest with ramdisk based guest using
kvm tool.
Short version:
With bio-based IO path, sequential read/write, random read/write
IOPS boost : 28%, 24%, 21%, 16%
Latency improvement: 32%, 17%, 21%, 16%
Long version:
With bio-based IO path:
seq-read : io=2048.0MB, bw=116996KB/s, iops=233991 , runt= 17925msec
seq-write : io=2048.0MB, bw=100829KB/s, iops=201658 , runt= 20799msec
rand-read : io=3095.7MB, bw=112134KB/s, iops=224268 , runt= 28269msec
rand-write: io=3095.7MB, bw=96198KB/s, iops=192396 , runt= 32952msec
clat (usec): min=0 , max=2631.6K, avg=58716.99, stdev=191377.30
clat (usec): min=0 , max=1753.2K, avg=66423.25, stdev=81774.35
clat (usec): min=0 , max=2915.5K, avg=61685.70, stdev=120598.39
clat (usec): min=0 , max=1933.4K, avg=76935.12, stdev=96603.45
cpu : usr=74.08%, sys=703.84%, ctx=29661403, majf=21354, minf=22460954
cpu : usr=70.92%, sys=702.81%, ctx=77219828, majf=13980, minf=27713137
cpu : usr=72.23%, sys=695.37%, ctx=88081059, majf=18475, minf=28177648
cpu : usr=69.69%, sys=654.13%, ctx=145476035, majf=15867, minf=26176375
With request-based IO path:
seq-read : io=2048.0MB, bw=91074KB/s, iops=182147 , runt= 23027msec
seq-write : io=2048.0MB, bw=80725KB/s, iops=161449 , runt= 25979msec
rand-read : io=3095.7MB, bw=92106KB/s, iops=184211 , runt= 34416msec
rand-write: io=3095.7MB, bw=82815KB/s, iops=165630 , runt= 38277msec
clat (usec): min=0 , max=1932.4K, avg=77824.17, stdev=170339.49
clat (usec): min=0 , max=2510.2K, avg=78023.96, stdev=146949.15
clat (usec): min=0 , max=3037.2K, avg=74746.53, stdev=128498.27
clat (usec): min=0 , max=1363.4K, avg=89830.75, stdev=114279.68
cpu : usr=53.28%, sys=724.19%, ctx=37988895, majf=17531, minf=23577622
cpu : usr=49.03%, sys=633.20%, ctx=205935380, majf=18197, minf=27288959
cpu : usr=55.78%, sys=722.40%, ctx=101525058, majf=19273, minf=28067082
cpu : usr=56.55%, sys=690.83%, ctx=228205022, majf=18039, minf=26551985
2) Fio test is performed in a 8 vcpu guest with Fusion-IO based guest using
kvm tool.
Short version:
With bio-based IO path, sequential read/write, random read/write
IOPS boost : 11%, 11%, 13%, 10%
Latency improvement: 10%, 10%, 12%, 10%
Long Version:
With bio-based IO path:
read : io=2048.0MB, bw=58920KB/s, iops=117840 , runt= 35593msec
write: io=2048.0MB, bw=64308KB/s, iops=128616 , runt= 32611msec
read : io=3095.7MB, bw=59633KB/s, iops=119266 , runt= 53157msec
write: io=3095.7MB, bw=62993KB/s, iops=125985 , runt= 50322msec
clat (usec): min=0 , max=1284.3K, avg=128109.01, stdev=71513.29
clat (usec): min=94 , max=962339 , avg=116832.95, stdev=65836.80
clat (usec): min=0 , max=1846.6K, avg=128509.99, stdev=89575.07
clat (usec): min=0 , max=2256.4K, avg=121361.84, stdev=82747.25
cpu : usr=56.79%, sys=421.70%, ctx=147335118, majf=21080, minf=19852517
cpu : usr=61.81%, sys=455.53%, ctx=143269950, majf=16027, minf=24800604
cpu : usr=63.10%, sys=455.38%, ctx=178373538, majf=16958, minf=24822612
cpu : usr=62.04%, sys=453.58%, ctx=226902362, majf=16089, minf=23278105
With request-based IO path:
read : io=2048.0MB, bw=52896KB/s, iops=105791 , runt= 39647msec
write: io=2048.0MB, bw=57856KB/s, iops=115711 , runt= 36248msec
read : io=3095.7MB, bw=52387KB/s, iops=104773 , runt= 60510msec
write: io=3095.7MB, bw=57310KB/s, iops=114619 , runt= 55312msec
clat (usec): min=0 , max=1532.6K, avg=142085.62, stdev=109196.84
clat (usec): min=0 , max=1487.4K, avg=129110.71, stdev=114973.64
clat (usec): min=0 , max=1388.6K, avg=145049.22, stdev=107232.55
clat (usec): min=0 , max=1465.9K, avg=133585.67, stdev=110322.95
cpu : usr=44.08%, sys=590.71%, ctx=451812322, majf=14841, minf=17648641
cpu : usr=48.73%, sys=610.78%, ctx=418953997, majf=22164, minf=26850689
cpu : usr=45.58%, sys=581.16%, ctx=714079216, majf=21497, minf=22558223
cpu : usr=48.40%, sys=599.65%, ctx=656089423, majf=16393, minf=23824409
3) Fio test is performed in a 8 vcpu guest with normal SATA based guest
using kvm tool.
Short version:
With bio-based IO path, sequential read/write, random read/write
IOPS boost : -10%, -10%, 4.4%, 0.5%
Latency improvement: -12%, -15%, 2.5%, 0.8%
Long Version:
With bio-based IO path:
read : io=124812KB, bw=36537KB/s, iops=9060 , runt= 3416msec
write: io=169180KB, bw=24406KB/s, iops=6065 , runt= 6932msec
read : io=256200KB, bw=2089.3KB/s, iops=520 , runt=122630msec
write: io=257988KB, bw=1545.7KB/s, iops=384 , runt=166910msec
clat (msec): min=1 , max=1527 , avg=28.06, stdev=89.54
clat (msec): min=2 , max=344 , avg=41.12, stdev=38.70
clat (msec): min=8 , max=1984 , avg=490.63, stdev=207.28
clat (msec): min=33 , max=4131 , avg=659.19, stdev=304.71
cpu : usr=4.85%, sys=17.15%, ctx=31593, majf=0, minf=7
cpu : usr=3.04%, sys=11.45%, ctx=39377, majf=0, minf=0
cpu : usr=0.47%, sys=1.59%, ctx=262986, majf=0, minf=16
cpu : usr=0.47%, sys=1.46%, ctx=337410, majf=0, minf=0
With request-based IO path:
read : io=150120KB, bw=40420KB/s, iops=10037 , runt= 3714msec
write: io=194932KB, bw=27029KB/s, iops=6722 , runt= 7212msec
read : io=257136KB, bw=2001.1KB/s, iops=498 , runt=128443msec
write: io=258276KB, bw=1537.2KB/s, iops=382 , runt=168028msec
clat (msec): min=1 , max=1542 , avg=24.84, stdev=32.45
clat (msec): min=3 , max=628 , avg=35.62, stdev=39.71
clat (msec): min=8 , max=2540 , avg=503.28, stdev=236.97
clat (msec): min=41 , max=4398 , avg=653.88, stdev=302.61
cpu : usr=3.91%, sys=15.75%, ctx=26968, majf=0, minf=23
cpu : usr=2.50%, sys=10.56%, ctx=19090, majf=0, minf=0
cpu : usr=0.16%, sys=0.43%, ctx=20159, majf=0, minf=16
cpu : usr=0.18%, sys=0.53%, ctx=81364, majf=0, minf=0
How to use:
-----------------------------
Add 'virtio_blk.use_bio=1' to kernel cmdline or 'modprobe virtio_blk
use_bio=1' to enable ->make_request_fn() based I/O path.
Cc: Rusty Russell <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Christoph Hellwig <[email protected]>
Signed-off-by: Minchan Kim <[email protected]>
Signed-off-by: Asias He <[email protected]>
Acked-by: Rusty Russell <[email protected]>
---
drivers/block/virtio_blk.c | 203 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 163 insertions(+), 40 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index c0bbeb4..95cfeed 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -14,6 +14,9 @@
#define PART_BITS 4
+static bool use_bio;
+module_param(use_bio, bool, S_IRUGO);
+
static int major;
static DEFINE_IDA(vd_index_ida);
@@ -23,6 +26,7 @@ struct virtio_blk
{
struct virtio_device *vdev;
struct virtqueue *vq;
+ wait_queue_head_t queue_wait;
/* The disk structure for the kernel. */
struct gendisk *disk;
@@ -51,53 +55,87 @@ struct virtio_blk
struct virtblk_req
{
struct request *req;
+ struct bio *bio;
struct virtio_blk_outhdr out_hdr;
struct virtio_scsi_inhdr in_hdr;
u8 status;
+ struct scatterlist sg[];
};
-static void blk_done(struct virtqueue *vq)
+static inline int virtblk_result(struct virtblk_req *vbr)
+{
+ switch (vbr->status) {
+ case VIRTIO_BLK_S_OK:
+ return 0;
+ case VIRTIO_BLK_S_UNSUPP:
+ return -ENOTTY;
+ default:
+ return -EIO;
+ }
+}
+
+static inline void virtblk_request_done(struct virtio_blk *vblk,
+ struct virtblk_req *vbr)
+{
+ struct request *req = vbr->req;
+ int error = virtblk_result(vbr);
+
+ if (req->cmd_type == REQ_TYPE_BLOCK_PC) {
+ req->resid_len = vbr->in_hdr.residual;
+ req->sense_len = vbr->in_hdr.sense_len;
+ req->errors = vbr->in_hdr.errors;
+ } else if (req->cmd_type == REQ_TYPE_SPECIAL) {
+ req->errors = (error != 0);
+ }
+
+ __blk_end_request_all(req, error);
+ mempool_free(vbr, vblk->pool);
+}
+
+static inline void virtblk_bio_done(struct virtio_blk *vblk,
+ struct virtblk_req *vbr)
+{
+ bio_endio(vbr->bio, virtblk_result(vbr));
+ mempool_free(vbr, vblk->pool);
+}
+
+static void virtblk_done(struct virtqueue *vq)
{
struct virtio_blk *vblk = vq->vdev->priv;
+ unsigned long bio_done = 0, req_done = 0;
struct virtblk_req *vbr;
- unsigned int len;
unsigned long flags;
+ unsigned int len;
spin_lock_irqsave(vblk->disk->queue->queue_lock, flags);
while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
- int error;
-
- switch (vbr->status) {
- case VIRTIO_BLK_S_OK:
- error = 0;
- break;
- case VIRTIO_BLK_S_UNSUPP:
- error = -ENOTTY;
- break;
- default:
- error = -EIO;
- break;
- }
-
- switch (vbr->req->cmd_type) {
- case REQ_TYPE_BLOCK_PC:
- vbr->req->resid_len = vbr->in_hdr.residual;
- vbr->req->sense_len = vbr->in_hdr.sense_len;
- vbr->req->errors = vbr->in_hdr.errors;
- break;
- case REQ_TYPE_SPECIAL:
- vbr->req->errors = (error != 0);
- break;
- default:
- break;
+ if (vbr->bio) {
+ virtblk_bio_done(vblk, vbr);
+ bio_done++;
+ } else {
+ virtblk_request_done(vblk, vbr);
+ req_done++;
}
-
- __blk_end_request_all(vbr->req, error);
- mempool_free(vbr, vblk->pool);
}
/* In case queue is stopped waiting for more buffers. */
- blk_start_queue(vblk->disk->queue);
+ if (req_done)
+ blk_start_queue(vblk->disk->queue);
spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags);
+
+ if (bio_done)
+ wake_up(&vblk->queue_wait);
+}
+
+static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
+ gfp_t gfp_mask)
+{
+ struct virtblk_req *vbr;
+
+ vbr = mempool_alloc(vblk->pool, gfp_mask);
+ if (vbr && use_bio)
+ sg_init_table(vbr->sg, vblk->sg_elems);
+
+ return vbr;
}
static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
@@ -106,13 +144,13 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
unsigned long num, out = 0, in = 0;
struct virtblk_req *vbr;
- vbr = mempool_alloc(vblk->pool, GFP_ATOMIC);
+ vbr = virtblk_alloc_req(vblk, GFP_ATOMIC);
if (!vbr)
/* When another request finishes we'll try again. */
return false;
vbr->req = req;
-
+ vbr->bio = NULL;
if (req->cmd_flags & REQ_FLUSH) {
vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
vbr->out_hdr.sector = 0;
@@ -172,7 +210,8 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
}
}
- if (virtqueue_add_buf(vblk->vq, vblk->sg, out, in, vbr, GFP_ATOMIC)<0) {
+ if (virtqueue_add_buf(vblk->vq, vblk->sg, out, in, vbr,
+ GFP_ATOMIC) < 0) {
mempool_free(vbr, vblk->pool);
return false;
}
@@ -180,7 +219,7 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
return true;
}
-static void do_virtblk_request(struct request_queue *q)
+static void virtblk_request(struct request_queue *q)
{
struct virtio_blk *vblk = q->queuedata;
struct request *req;
@@ -203,6 +242,82 @@ static void do_virtblk_request(struct request_queue *q)
virtqueue_kick(vblk->vq);
}
+static void virtblk_add_buf_wait(struct virtio_blk *vblk,
+ struct virtblk_req *vbr,
+ unsigned long out,
+ unsigned long in)
+{
+ DEFINE_WAIT(wait);
+
+ for (;;) {
+ prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
+ TASK_UNINTERRUPTIBLE);
+
+ spin_lock_irq(vblk->disk->queue->queue_lock);
+ if (virtqueue_add_buf(vblk->vq, vbr->sg, out, in, vbr,
+ GFP_ATOMIC) < 0) {
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+ io_schedule();
+ } else {
+ virtqueue_kick(vblk->vq);
+ spin_unlock_irq(vblk->disk->queue->queue_lock);
+ break;
+ }
+
+ }
+
+ finish_wait(&vblk->queue_wait, &wait);
+}
+
+static void virtblk_make_request(struct request_queue *q, struct bio *bio)
+{
+ struct virtio_blk *vblk = q->queuedata;
+ unsigned int num, out = 0, in = 0;
+ struct virtblk_req *vbr;
+
+ BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
+ BUG_ON(bio->bi_rw & (REQ_FLUSH | REQ_FUA));
+
+ vbr = virtblk_alloc_req(vblk, GFP_NOIO);
+ if (!vbr) {
+ bio_endio(bio, -ENOMEM);
+ return;
+ }
+
+ vbr->bio = bio;
+ vbr->req = NULL;
+ vbr->out_hdr.type = 0;
+ vbr->out_hdr.sector = bio->bi_sector;
+ vbr->out_hdr.ioprio = bio_prio(bio);
+
+ sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
+
+ num = blk_bio_map_sg(q, bio, vbr->sg + out);
+
+ sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
+ sizeof(vbr->status));
+
+ if (num) {
+ if (bio->bi_rw & REQ_WRITE) {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
+ out += num;
+ } else {
+ vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
+ in += num;
+ }
+ }
+
+ 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);
+}
+
/* return id (s/n) string for *disk to *id_str
*/
static int virtblk_get_id(struct gendisk *disk, char *id_str)
@@ -360,7 +475,7 @@ static int init_vq(struct virtio_blk *vblk)
int err = 0;
/* We expect one virtqueue, for output. */
- vblk->vq = virtio_find_single_vq(vblk->vdev, blk_done, "requests");
+ vblk->vq = virtio_find_single_vq(vblk->vdev, virtblk_done, "requests");
if (IS_ERR(vblk->vq))
err = PTR_ERR(vblk->vq);
@@ -414,7 +529,7 @@ 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)
+ if (writeback && !use_bio)
blk_queue_flush(vblk->disk->queue, REQ_FLUSH);
else
blk_queue_flush(vblk->disk->queue, 0);
@@ -477,6 +592,8 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
struct virtio_blk *vblk;
struct request_queue *q;
int err, index;
+ int pool_size;
+
u64 cap;
u32 v, blk_size, sg_elems, opt_io_size;
u16 min_io_size;
@@ -506,10 +623,12 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
goto out_free_index;
}
+ init_waitqueue_head(&vblk->queue_wait);
vblk->vdev = vdev;
vblk->sg_elems = sg_elems;
sg_init_table(vblk->sg, vblk->sg_elems);
mutex_init(&vblk->config_lock);
+
INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
vblk->config_enable = true;
@@ -517,7 +636,10 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
if (err)
goto out_free_vblk;
- vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
+ pool_size = sizeof(struct virtblk_req);
+ if (use_bio)
+ pool_size += sizeof(struct scatterlist) * sg_elems;
+ vblk->pool = mempool_create_kmalloc_pool(1, pool_size);
if (!vblk->pool) {
err = -ENOMEM;
goto out_free_vq;
@@ -530,12 +652,14 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
goto out_mempool;
}
- q = vblk->disk->queue = blk_init_queue(do_virtblk_request, NULL);
+ q = vblk->disk->queue = blk_init_queue(virtblk_request, NULL);
if (!q) {
err = -ENOMEM;
goto out_put_disk;
}
+ if (use_bio)
+ blk_queue_make_request(q, virtblk_make_request);
q->queuedata = vblk;
virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
@@ -620,7 +744,6 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
if (!err && opt_io_size)
blk_queue_io_opt(q, blk_size * opt_io_size);
-
add_disk(vblk->disk);
err = device_create_file(disk_to_dev(vblk->disk), &dev_attr_serial);
if (err)
--
1.7.11.2