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Message-ID: <56188F4A.3060802@oracle.com> Date: Sat, 10 Oct 2015 12:08:42 +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 7/9] xen/blkback: separate ring information out of struct xen_blkif On 10/05/2015 10:55 PM, Roger Pau Monné wrote: > 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. > Hi Roger, I realize it would make things complicate if making persistent grant per-device instead of per-queue. Extra locks are required to protect the per-device pool on both blkfront and blkback. AFAIR, there was a discussion before about dropping persistent grant map at all. The only reason we left this feature was backward compatibility. So that I think we should not complicate xen-block code any more because of a going to be dropped feature. How about disable feature-persistent if multi-queue was used? -- Regards, -Bob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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