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Date: Mon, 5 Oct 2015 16:55:31 +0200
From: Roger Pau Monné <roger.pau@...rix.com>
To: Bob Liu <bob.liu@...cle.com>, <xen-devel@...ts.xen.org>
CC: <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 7/9] xen/blkback: separate ring information out of
struct xen_blkif
El 05/09/15 a les 14.39, Bob Liu ha escrit:
> Split per ring information to an new structure:xen_blkif_ring, so that one vbd
> device can associate with one or more rings/hardware queues.
>
> This patch is a preparation for supporting multi hardware queues/rings.
>
> Signed-off-by: Arianna Avanzini <avanzini.arianna@...il.com>
> Signed-off-by: Bob Liu <bob.liu@...cle.com>
> ---
> drivers/block/xen-blkback/blkback.c | 365 ++++++++++++++++++-----------------
> drivers/block/xen-blkback/common.h | 52 +++--
> drivers/block/xen-blkback/xenbus.c | 130 +++++++------
> 3 files changed, 295 insertions(+), 252 deletions(-)
>
> diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> index 954c002..fd02240 100644
> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -113,71 +113,71 @@ module_param(log_stats, int, 0644);
> /* Number of free pages to remove on each call to gnttab_free_pages */
> #define NUM_BATCH_FREE_PAGES 10
>
> -static inline int get_free_page(struct xen_blkif *blkif, struct page **page)
> +static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page)
> {
> unsigned long flags;
>
> - spin_lock_irqsave(&blkif->free_pages_lock, flags);
> - if (list_empty(&blkif->free_pages)) {
> - BUG_ON(blkif->free_pages_num != 0);
> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
> + spin_lock_irqsave(&ring->free_pages_lock, flags);
> + if (list_empty(&ring->free_pages)) {
I'm afraid the pool of free pages should be per-device, not per-ring.
> + BUG_ON(ring->free_pages_num != 0);
> + spin_unlock_irqrestore(&ring->free_pages_lock, flags);
> return gnttab_alloc_pages(1, page);
> }
> - BUG_ON(blkif->free_pages_num == 0);
> - page[0] = list_first_entry(&blkif->free_pages, struct page, lru);
> + BUG_ON(ring->free_pages_num == 0);
> + page[0] = list_first_entry(&ring->free_pages, struct page, lru);
> list_del(&page[0]->lru);
> - blkif->free_pages_num--;
> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
> + ring->free_pages_num--;
> + spin_unlock_irqrestore(&ring->free_pages_lock, flags);
>
> return 0;
> }
>
> -static inline void put_free_pages(struct xen_blkif *blkif, struct page **page,
> +static inline void put_free_pages(struct xen_blkif_ring *ring, struct page **page,
> int num)
> {
> unsigned long flags;
> int i;
>
> - spin_lock_irqsave(&blkif->free_pages_lock, flags);
> + spin_lock_irqsave(&ring->free_pages_lock, flags);
> for (i = 0; i < num; i++)
> - list_add(&page[i]->lru, &blkif->free_pages);
> - blkif->free_pages_num += num;
> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
> + list_add(&page[i]->lru, &ring->free_pages);
> + ring->free_pages_num += num;
> + spin_unlock_irqrestore(&ring->free_pages_lock, flags);
> }
>
> -static inline void shrink_free_pagepool(struct xen_blkif *blkif, int num)
> +static inline void shrink_free_pagepool(struct xen_blkif_ring *ring, int num)
> {
> /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */
> struct page *page[NUM_BATCH_FREE_PAGES];
> unsigned int num_pages = 0;
> unsigned long flags;
>
> - spin_lock_irqsave(&blkif->free_pages_lock, flags);
> - while (blkif->free_pages_num > num) {
> - BUG_ON(list_empty(&blkif->free_pages));
> - page[num_pages] = list_first_entry(&blkif->free_pages,
> + spin_lock_irqsave(&ring->free_pages_lock, flags);
> + while (ring->free_pages_num > num) {
> + BUG_ON(list_empty(&ring->free_pages));
> + page[num_pages] = list_first_entry(&ring->free_pages,
> struct page, lru);
> list_del(&page[num_pages]->lru);
> - blkif->free_pages_num--;
> + ring->free_pages_num--;
> if (++num_pages == NUM_BATCH_FREE_PAGES) {
> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
> + spin_unlock_irqrestore(&ring->free_pages_lock, flags);
> gnttab_free_pages(num_pages, page);
> - spin_lock_irqsave(&blkif->free_pages_lock, flags);
> + spin_lock_irqsave(&ring->free_pages_lock, flags);
> num_pages = 0;
> }
> }
> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags);
> + spin_unlock_irqrestore(&ring->free_pages_lock, flags);
> if (num_pages != 0)
> gnttab_free_pages(num_pages, page);
> }
>
> #define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page)))
>
> -static int do_block_io_op(struct xen_blkif *blkif);
> -static int dispatch_rw_block_io(struct xen_blkif *blkif,
> +static int do_block_io_op(struct xen_blkif_ring *ring);
> +static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
> struct blkif_request *req,
> struct pending_req *pending_req);
> -static void make_response(struct xen_blkif *blkif, u64 id,
> +static void make_response(struct xen_blkif_ring *ring, u64 id,
> unsigned short op, int st);
>
> #define foreach_grant_safe(pos, n, rbtree, node) \
> @@ -198,19 +198,19 @@ static void make_response(struct xen_blkif *blkif, u64 id,
> * bit operations to modify the flags of a persistent grant and to count
> * the number of used grants.
> */
> -static int add_persistent_gnt(struct xen_blkif *blkif,
> +static int add_persistent_gnt(struct xen_blkif_ring *ring,
> struct persistent_gnt *persistent_gnt)
> {
> struct rb_node **new = NULL, *parent = NULL;
> struct persistent_gnt *this;
>
> - if (blkif->persistent_gnt_c >= xen_blkif_max_pgrants) {
> - if (!blkif->vbd.overflow_max_grants)
> - blkif->vbd.overflow_max_grants = 1;
> + if (ring->persistent_gnt_c >= xen_blkif_max_pgrants) {
> + if (!ring->blkif->vbd.overflow_max_grants)
> + ring->blkif->vbd.overflow_max_grants = 1;
The same for the pool of persistent grants, it should be per-device and
not per-ring.
And I think this issue is far worse than the others, because a frontend
might use a persistent grant on different queues, forcing the backend
map the grant several times for each queue, this is not acceptable IMO.
Roger.
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