From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Liu Subject: Re: [PATCH v3 7/9] xen/blkback: separate ring information out of struct xen_blkif Date: Sat, 10 Oct 2015 12:08:42 +0800 Message-ID: <56188F4A.3060802__6921.81612034819$1444450283$gmane$org@oracle.com> References: <1441456782-31318-1-git-send-email-bob.liu@oracle.com> <1441456782-31318-8-git-send-email-bob.liu@oracle.com> <56128F54.1090907@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <56128F54.1090907@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: =?windows-1252?Q?Roger_Pau_Monn=E9?= Cc: hch@infradead.org, felipe.franciosi@citrix.com, rafal.mielniczuk@citrix.com, linux-kernel@vger.kernel.org, xen-devel@lists.xen.org, axboe@fb.com, jonathan.davies@citrix.com, david.vrabel@citrix.com, avanzini.arianna@gmail.com, boris.ostrovsky@oracle.com List-Id: xen-devel@lists.xenproject.org On 10/05/2015 10:55 PM, Roger Pau Monn=E9 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 o= ne 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 >> Signed-off-by: Bob Liu >> --- >> 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-blk= back/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 pag= e **page) >> { >> unsigned long flags; >> = >> - spin_lock_irqsave(&blkif->free_pages_lock, flags); >> - if (list_empty(&blkif->free_pages)) { >> - BUG_ON(blkif->free_pages_num !=3D 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 !=3D 0); >> + spin_unlock_irqrestore(&ring->free_pages_lock, flags); >> return gnttab_alloc_pages(1, page); >> } >> - BUG_ON(blkif->free_pages_num =3D=3D 0); >> - page[0] =3D list_first_entry(&blkif->free_pages, struct page, lru); >> + BUG_ON(ring->free_pages_num =3D=3D 0); >> + page[0] =3D 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 p= age **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 =3D 0; i < num; i++) >> - list_add(&page[i]->lru, &blkif->free_pages); >> - blkif->free_pages_num +=3D num; >> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags); >> + list_add(&page[i]->lru, &ring->free_pages); >> + ring->free_pages_num +=3D num; >> + spin_unlock_irqrestore(&ring->free_pages_lock, flags); >> } >> = >> -static inline void shrink_free_pagepool(struct xen_blkif *blkif, int nu= m) >> +static inline void shrink_free_pagepool(struct xen_blkif_ring *ring, in= t num) >> { >> /* Remove requested pages in batches of NUM_BATCH_FREE_PAGES */ >> struct page *page[NUM_BATCH_FREE_PAGES]; >> unsigned int num_pages =3D 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] =3D 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] =3D 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 =3D=3D 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 =3D 0; >> } >> } >> - spin_unlock_irqrestore(&blkif->free_pages_lock, flags); >> + spin_unlock_irqrestore(&ring->free_pages_lock, flags); >> if (num_pages !=3D 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 =3D NULL, *parent =3D NULL; >> struct persistent_gnt *this; >> = >> - if (blkif->persistent_gnt_c >=3D xen_blkif_max_pgrants) { >> - if (!blkif->vbd.overflow_max_grants) >> - blkif->vbd.overflow_max_grants =3D 1; >> + if (ring->persistent_gnt_c >=3D xen_blkif_max_pgrants) { >> + if (!ring->blkif->vbd.overflow_max_grants) >> + ring->blkif->vbd.overflow_max_grants =3D 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-de= vice instead of per-queue. Extra locks are required to protect the per-device pool on both blkfront an= d 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