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Date: Wed, 07 Oct 2015 18:50:44 +0800
From: Bob Liu <bob.liu@...cle.com>
To: Roger Pau Monné <roger.pau@...rix.com>
CC: xen-devel@...ts.xen.org, david.vrabel@...rix.com,
linux-kernel@...r.kernel.org, konrad.wilk@...cle.com,
felipe.franciosi@...rix.com, axboe@...com, hch@...radead.org,
avanzini.arianna@...il.com, rafal.mielniczuk@...rix.com,
boris.ostrovsky@...cle.com, jonathan.davies@...rix.com
Subject: Re: [PATCH v3 8/9] xen/blkback: pseudo support for multi hardware
queues/rings
On 10/05/2015 11:08 PM, Roger Pau Monné wrote:
> El 05/09/15 a les 14.39, Bob Liu ha escrit:
>> Prepare patch for multi hardware queues/rings, the ring number was set to 1 by
>> force.
>
> This should be:
>
> Preparatory patch for multiple hardware queues (rings). The number of
> rings is unconditionally set to 1.
>
> But frankly this description is not helpful at all, you should describe
> the preparatory changes and why you need them.
>
Will update, the purpose is just to make each patch smaller and more readable.
>>
>> Signed-off-by: Arianna Avanzini <avanzini.arianna@...il.com>
>> Signed-off-by: Bob Liu <bob.liu@...cle.com>
>> ---
>> drivers/block/xen-blkback/common.h | 3 +-
>> drivers/block/xen-blkback/xenbus.c | 328 +++++++++++++++++++++++-------------
>> 2 files changed, 209 insertions(+), 122 deletions(-)
>>
>> diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
>> index cc253d4..ba058a0 100644
>> --- a/drivers/block/xen-blkback/common.h
>> +++ b/drivers/block/xen-blkback/common.h
>> @@ -339,7 +339,8 @@ struct xen_blkif {
>> unsigned long long st_wr_sect;
>> unsigned int nr_ring_pages;
>> /* All rings for this device */
>> - struct xen_blkif_ring ring;
>> + struct xen_blkif_ring *rings;
>> + unsigned int nr_rings;
>> };
>>
>> struct seg_buf {
>> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
>> index 6482ee3..04b8d0d 100644
>> --- a/drivers/block/xen-blkback/xenbus.c
>> +++ b/drivers/block/xen-blkback/xenbus.c
>> @@ -26,6 +26,7 @@
>> /* Enlarge the array size in order to fully show blkback name. */
>> #define BLKBACK_NAME_LEN (20)
>> #define RINGREF_NAME_LEN (20)
>> +#define RINGREF_NAME_LEN (20)
>
> Duplicate define?
>
Will update.
>>
>> struct backend_info {
>> struct xenbus_device *dev;
>> @@ -84,11 +85,13 @@ static int blkback_name(struct xen_blkif *blkif, char *buf)
>>
>> static void xen_update_blkif_status(struct xen_blkif *blkif)
>> {
>> - int err;
>> + int err, i;
>> char name[BLKBACK_NAME_LEN];
>> + struct xen_blkif_ring *ring;
>> + char per_ring_name[BLKBACK_NAME_LEN + 2];
>
> Hm, why don't you just add + 2 to the place where BLKBACK_NAME_LEN is
> defined and use the same character array ("name")? This is just a waste
> of stack.
>
per_ring_name = name + 'queue number';
If reuse name[], I'm not sure whether
snprintf(name, BLKBACK_NAME_LEN + 2, "%s-%d", name, i); can work.
>>
>> /* Not ready to connect? */
>> - if (!blkif->ring.irq || !blkif->vbd.bdev)
>> + if (!blkif->rings || !blkif->rings[0].irq || !blkif->vbd.bdev)
>> return;
>>
>> /* Already connected? */
>> @@ -113,19 +116,68 @@ static void xen_update_blkif_status(struct xen_blkif *blkif)
>> }
>> invalidate_inode_pages2(blkif->vbd.bdev->bd_inode->i_mapping);
>>
>> - blkif->ring.xenblkd = kthread_run(xen_blkif_schedule, &blkif->ring, "%s", name);
>> - if (IS_ERR(blkif->ring.xenblkd)) {
>> - err = PTR_ERR(blkif->ring.xenblkd);
>> - blkif->ring.xenblkd = NULL;
>> - xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
>> - return;
>> + if (blkif->nr_rings == 1) {
>> + blkif->rings[0].xenblkd = kthread_run(xen_blkif_schedule, &blkif->rings[0], "%s", name);
>> + if (IS_ERR(blkif->rings[0].xenblkd)) {
>> + err = PTR_ERR(blkif->rings[0].xenblkd);
>> + blkif->rings[0].xenblkd = NULL;
>> + xenbus_dev_error(blkif->be->dev, err, "start xenblkd");
>> + return;
>> + }
>> + } else {
>> + for (i = 0; i < blkif->nr_rings; i++) {
>> + snprintf(per_ring_name, BLKBACK_NAME_LEN + 2, "%s-%d", name, i);
>> + ring = &blkif->rings[i];
>> + ring->xenblkd = kthread_run(xen_blkif_schedule, ring, "%s", per_ring_name);
>> + if (IS_ERR(ring->xenblkd)) {
>> + err = PTR_ERR(ring->xenblkd);
>> + ring->xenblkd = NULL;
>> + xenbus_dev_error(blkif->be->dev, err,
>> + "start %s xenblkd", per_ring_name);
>> + return;
>> + }
>> + }
>> + }
>> +}
>> +
>> +static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
>> +{
>> + struct xen_blkif_ring *ring;
>> + int r;
>> +
>> + blkif->rings = kzalloc(blkif->nr_rings * sizeof(struct xen_blkif_ring), GFP_KERNEL);
>> + if (!blkif->rings)
>> + return -ENOMEM;
>> +
>> + for (r = 0; r < blkif->nr_rings; r++) {
>> + ring = &blkif->rings[r];
>> +
>> + spin_lock_init(&ring->blk_ring_lock);
>> + init_waitqueue_head(&ring->wq);
>> + ring->st_print = jiffies;
>> + ring->persistent_gnts.rb_node = NULL;
>> + spin_lock_init(&ring->free_pages_lock);
>> + INIT_LIST_HEAD(&ring->free_pages);
>> + INIT_LIST_HEAD(&ring->persistent_purge_list);
>> + ring->free_pages_num = 0;
>> + atomic_set(&ring->persistent_gnt_in_use, 0);
>> + atomic_set(&ring->inflight, 0);
>> + INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants);
>> + INIT_LIST_HEAD(&ring->pending_free);
>> +
>> + spin_lock_init(&ring->pending_free_lock);
>> + init_waitqueue_head(&ring->pending_free_wq);
>> + init_waitqueue_head(&ring->shutdown_wq);
>
> I've already commented on the previous patch, but a bunch of this needs
> to be per-device rather than per-ring.
>
Will update and all other comments.
Thanks
-Bob
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