diff options
Diffstat (limited to 'drivers/block/xen-blkback/blkback.c')
-rw-r--r-- | drivers/block/xen-blkback/blkback.c | 286 |
1 files changed, 165 insertions, 121 deletions
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index f7526db..8245c6b 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -63,6 +63,21 @@ static int xen_blkif_reqs = 64; module_param_named(reqs, xen_blkif_reqs, int, 0); MODULE_PARM_DESC(reqs, "Number of blkback requests to allocate"); +/* + * Maximum number of unused free pages to keep in the internal buffer. + * Setting this to a value too low will reduce memory used in each backend, + * but can have a performance penalty. + * + * A sane value is xen_blkif_reqs * BLKIF_MAX_SEGMENTS_PER_REQUEST, but can + * be set to a lower value that might degrade performance on some intensive + * IO workloads. + */ + +static int xen_blkif_max_buffer_pages = 704; +module_param_named(max_buffer_pages, xen_blkif_max_buffer_pages, int, 0644); +MODULE_PARM_DESC(max_buffer_pages, +"Maximum number of free pages to keep in each block backend buffer"); + /* Run-time switchable: /sys/module/blkback/parameters/ */ static unsigned int log_stats; module_param(log_stats, int, 0644); @@ -82,10 +97,14 @@ struct pending_req { int status; struct list_head free_list; DECLARE_BITMAP(unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST); + struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; }; #define BLKBACK_INVALID_HANDLE (~0) +/* Number of free pages to remove on each call to free_xenballooned_pages */ +#define NUM_BATCH_FREE_PAGES 10 + struct xen_blkbk { struct pending_req *pending_reqs; /* List of all 'pending_req' available */ @@ -93,8 +112,6 @@ struct xen_blkbk { /* And its spinlock. */ spinlock_t pending_free_lock; wait_queue_head_t pending_free_wq; - /* The list of all pages that are available. */ - struct page **pending_pages; /* And the grant handles that are available. */ grant_handle_t *pending_grant_handles; }; @@ -143,14 +160,66 @@ static inline int vaddr_pagenr(struct pending_req *req, int seg) BLKIF_MAX_SEGMENTS_PER_REQUEST + seg; } -#define pending_page(req, seg) pending_pages[vaddr_pagenr(req, seg)] +static inline int get_free_page(struct xen_blkif *blkif, 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); + return alloc_xenballooned_pages(1, page, false); + } + BUG_ON(blkif->free_pages_num == 0); + page[0] = list_first_entry(&blkif->free_pages, struct page, lru); + list_del(&page[0]->lru); + blkif->free_pages_num--; + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); -static inline unsigned long vaddr(struct pending_req *req, int seg) + return 0; +} + +static inline void put_free_pages(struct xen_blkif *blkif, struct page **page, + int num) { - unsigned long pfn = page_to_pfn(blkbk->pending_page(req, seg)); - return (unsigned long)pfn_to_kaddr(pfn); + unsigned long flags; + int i; + + spin_lock_irqsave(&blkif->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); +} + +static inline void shrink_free_pagepool(struct xen_blkif *blkif, 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, + struct page, lru); + list_del(&page[num_pages]->lru); + blkif->free_pages_num--; + if (++num_pages == NUM_BATCH_FREE_PAGES) { + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + free_xenballooned_pages(num_pages, page); + spin_lock_irqsave(&blkif->free_pages_lock, flags); + num_pages = 0; + } + } + spin_unlock_irqrestore(&blkif->free_pages_lock, flags); + if (num_pages != 0) + free_xenballooned_pages(num_pages, page); } +#define vaddr(page) ((unsigned long)pfn_to_kaddr(page_to_pfn(page))) + #define pending_handle(_req, _seg) \ (blkbk->pending_grant_handles[vaddr_pagenr(_req, _seg)]) @@ -170,7 +239,7 @@ static void make_response(struct xen_blkif *blkif, u64 id, (n) = (&(pos)->node != NULL) ? rb_next(&(pos)->node) : NULL) -static void add_persistent_gnt(struct rb_root *root, +static int add_persistent_gnt(struct rb_root *root, struct persistent_gnt *persistent_gnt) { struct rb_node **new = &(root->rb_node), *parent = NULL; @@ -186,14 +255,15 @@ static void add_persistent_gnt(struct rb_root *root, else if (persistent_gnt->gnt > this->gnt) new = &((*new)->rb_right); else { - pr_alert(DRV_PFX " trying to add a gref that's already in the tree\n"); - BUG(); + pr_alert_ratelimited(DRV_PFX " trying to add a gref that's already in the tree\n"); + return -EINVAL; } } /* Add new node and rebalance tree. */ rb_link_node(&(persistent_gnt->node), parent, new); rb_insert_color(&(persistent_gnt->node), root); + return 0; } static struct persistent_gnt *get_persistent_gnt(struct rb_root *root, @@ -215,7 +285,8 @@ static struct persistent_gnt *get_persistent_gnt(struct rb_root *root, return NULL; } -static void free_persistent_gnts(struct rb_root *root, unsigned int num) +static void free_persistent_gnts(struct xen_blkif *blkif, struct rb_root *root, + unsigned int num) { struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST]; struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; @@ -240,7 +311,7 @@ static void free_persistent_gnts(struct rb_root *root, unsigned int num) ret = gnttab_unmap_refs(unmap, NULL, pages, segs_to_unmap); BUG_ON(ret); - free_xenballooned_pages(segs_to_unmap, pages); + put_free_pages(blkif, pages, segs_to_unmap); segs_to_unmap = 0; } @@ -422,13 +493,19 @@ int xen_blkif_schedule(void *arg) if (do_block_io_op(blkif)) blkif->waiting_reqs = 1; + /* Shrink if we have more than xen_blkif_max_buffer_pages */ + shrink_free_pagepool(blkif, xen_blkif_max_buffer_pages); + if (log_stats && time_after(jiffies, blkif->st_print)) print_stats(blkif); } + /* Since we are shutting down remove all pages from the buffer */ + shrink_free_pagepool(blkif, 0 /* All */); + /* Free all persistent grant pages */ if (!RB_EMPTY_ROOT(&blkif->persistent_gnts)) - free_persistent_gnts(&blkif->persistent_gnts, + free_persistent_gnts(blkif, &blkif->persistent_gnts, blkif->persistent_gnt_c); BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts)); @@ -457,23 +534,25 @@ static void xen_blkbk_unmap(struct pending_req *req) struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; unsigned int i, invcount = 0; grant_handle_t handle; + struct xen_blkif *blkif = req->blkif; int ret; for (i = 0; i < req->nr_pages; i++) { if (!test_bit(i, req->unmap_seg)) continue; handle = pending_handle(req, i); + pages[invcount] = req->pages[i]; if (handle == BLKBACK_INVALID_HANDLE) continue; - gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i), + gnttab_set_unmap_op(&unmap[invcount], vaddr(pages[invcount]), GNTMAP_host_map, handle); pending_handle(req, i) = BLKBACK_INVALID_HANDLE; - pages[invcount] = virt_to_page(vaddr(req, i)); invcount++; } ret = gnttab_unmap_refs(unmap, NULL, pages, invcount); BUG_ON(ret); + put_free_pages(blkif, pages, invcount); } static int xen_blkbk_map(struct blkif_request *req, @@ -487,8 +566,7 @@ static int xen_blkbk_map(struct blkif_request *req, struct persistent_gnt *persistent_gnt = NULL; struct xen_blkif *blkif = pending_req->blkif; phys_addr_t addr = 0; - int i, j; - bool new_map; + int i, seg_idx, new_map_idx; int nseg = req->u.rw.nr_segments; int segs_to_map = 0; int ret = 0; @@ -517,68 +595,16 @@ static int xen_blkbk_map(struct blkif_request *req, * We are using persistent grants and * the grant is already mapped */ - new_map = false; - } else if (use_persistent_gnts && - blkif->persistent_gnt_c < - max_mapped_grant_pages(blkif->blk_protocol)) { - /* - * We are using persistent grants, the grant is - * not mapped but we have room for it - */ - new_map = true; - persistent_gnt = kmalloc( - sizeof(struct persistent_gnt), - GFP_KERNEL); - if (!persistent_gnt) - return -ENOMEM; - if (alloc_xenballooned_pages(1, &persistent_gnt->page, - false)) { - kfree(persistent_gnt); - return -ENOMEM; - } - persistent_gnt->gnt = req->u.rw.seg[i].gref; - persistent_gnt->handle = BLKBACK_INVALID_HANDLE; - - pages_to_gnt[segs_to_map] = - persistent_gnt->page; - addr = (unsigned long) pfn_to_kaddr( - page_to_pfn(persistent_gnt->page)); - - add_persistent_gnt(&blkif->persistent_gnts, - persistent_gnt); - blkif->persistent_gnt_c++; - pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n", - persistent_gnt->gnt, blkif->persistent_gnt_c, - max_mapped_grant_pages(blkif->blk_protocol)); - } else { - /* - * We are either using persistent grants and - * hit the maximum limit of grants mapped, - * or we are not using persistent grants. - */ - if (use_persistent_gnts && - !blkif->vbd.overflow_max_grants) { - blkif->vbd.overflow_max_grants = 1; - pr_alert(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n", - blkif->domid, blkif->vbd.handle); - } - new_map = true; - pages[i] = blkbk->pending_page(pending_req, i); - addr = vaddr(pending_req, i); - pages_to_gnt[segs_to_map] = - blkbk->pending_page(pending_req, i); - } - - if (persistent_gnt) { pages[i] = persistent_gnt->page; persistent_gnts[i] = persistent_gnt; } else { + if (get_free_page(blkif, &pages[i])) + goto out_of_memory; + addr = vaddr(pages[i]); + pages_to_gnt[segs_to_map] = pages[i]; persistent_gnts[i] = NULL; - } - - if (new_map) { flags = GNTMAP_host_map; - if (!persistent_gnt && + if (!use_persistent_gnts && (pending_req->operation != BLKIF_OP_READ)) flags |= GNTMAP_readonly; gnttab_set_map_op(&map[segs_to_map++], addr, @@ -598,48 +624,81 @@ static int xen_blkbk_map(struct blkif_request *req, * the page from the other domain. */ bitmap_zero(pending_req->unmap_seg, BLKIF_MAX_SEGMENTS_PER_REQUEST); - for (i = 0, j = 0; i < nseg; i++) { - if (!persistent_gnts[i] || - persistent_gnts[i]->handle == BLKBACK_INVALID_HANDLE) { + for (seg_idx = 0, new_map_idx = 0; seg_idx < nseg; seg_idx++) { + if (!persistent_gnts[seg_idx]) { /* This is a newly mapped grant */ - BUG_ON(j >= segs_to_map); - if (unlikely(map[j].status != 0)) { + BUG_ON(new_map_idx >= segs_to_map); + if (unlikely(map[new_map_idx].status != 0)) { pr_debug(DRV_PFX "invalid buffer -- could not remap it\n"); - map[j].handle = BLKBACK_INVALID_HANDLE; + pending_handle(pending_req, seg_idx) = BLKBACK_INVALID_HANDLE; ret |= 1; - if (persistent_gnts[i]) { - rb_erase(&persistent_gnts[i]->node, - &blkif->persistent_gnts); - blkif->persistent_gnt_c--; - kfree(persistent_gnts[i]); - persistent_gnts[i] = NULL; - } + new_map_idx++; + /* + * No need to set unmap_seg bit, since + * we can not unmap this grant because + * the handle is invalid. + */ + continue; } + pending_handle(pending_req, seg_idx) = map[new_map_idx].handle; + } else { + /* This grant is persistent and already mapped */ + goto next; } - if (persistent_gnts[i]) { - if (persistent_gnts[i]->handle == - BLKBACK_INVALID_HANDLE) { + if (use_persistent_gnts && + blkif->persistent_gnt_c < + max_mapped_grant_pages(blkif->blk_protocol)) { + /* + * We are using persistent grants, the grant is + * not mapped but we have room for it + */ + persistent_gnt = kmalloc(sizeof(struct persistent_gnt), + GFP_KERNEL); + if (!persistent_gnt) { /* - * If this is a new persistent grant - * save the handler + * If we don't have enough memory to + * allocate the persistent_gnt struct + * map this grant non-persistenly */ - persistent_gnts[i]->handle = map[j++].handle; + goto next_unmap; } - pending_handle(pending_req, i) = - persistent_gnts[i]->handle; - - if (ret) - continue; - } else { - pending_handle(pending_req, i) = map[j++].handle; - bitmap_set(pending_req->unmap_seg, i, 1); - - if (ret) - continue; + persistent_gnt->gnt = map[new_map_idx].ref; + persistent_gnt->handle = map[new_map_idx].handle; + persistent_gnt->page = pages[seg_idx]; + if (add_persistent_gnt(&blkif->persistent_gnts, + persistent_gnt)) { + kfree(persistent_gnt); + persistent_gnt = NULL; + goto next_unmap; + } + blkif->persistent_gnt_c++; + pr_debug(DRV_PFX " grant %u added to the tree of persistent grants, using %u/%u\n", + persistent_gnt->gnt, blkif->persistent_gnt_c, + max_mapped_grant_pages(blkif->blk_protocol)); + new_map_idx++; + goto next; + } + if (use_persistent_gnts && !blkif->vbd.overflow_max_grants) { + blkif->vbd.overflow_max_grants = 1; + pr_debug(DRV_PFX " domain %u, device %#x is using maximum number of persistent grants\n", + blkif->domid, blkif->vbd.handle); } - seg[i].offset = (req->u.rw.seg[i].first_sect << 9); +next_unmap: + /* + * We could not map this grant persistently, so use it as + * a non-persistent grant. + */ + bitmap_set(pending_req->unmap_seg, seg_idx, 1); + new_map_idx++; +next: + seg[seg_idx].offset = (req->u.rw.seg[seg_idx].first_sect << 9); } return ret; + +out_of_memory: + pr_alert(DRV_PFX "%s: out of memory\n", __func__); + put_free_pages(blkif, pages_to_gnt, segs_to_map); + return -ENOMEM; } static int dispatch_discard_io(struct xen_blkif *blkif, @@ -863,7 +922,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif, int operation; struct blk_plug plug; bool drain = false; - struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST]; + struct page **pages = pending_req->pages; switch (req->operation) { case BLKIF_OP_READ: @@ -1090,22 +1149,14 @@ static int __init xen_blkif_init(void) xen_blkif_reqs, GFP_KERNEL); blkbk->pending_grant_handles = kmalloc(sizeof(blkbk->pending_grant_handles[0]) * mmap_pages, GFP_KERNEL); - blkbk->pending_pages = kzalloc(sizeof(blkbk->pending_pages[0]) * - mmap_pages, GFP_KERNEL); - if (!blkbk->pending_reqs || !blkbk->pending_grant_handles || - !blkbk->pending_pages) { + if (!blkbk->pending_reqs || !blkbk->pending_grant_handles) { rc = -ENOMEM; goto out_of_memory; } for (i = 0; i < mmap_pages; i++) { blkbk->pending_grant_handles[i] = BLKBACK_INVALID_HANDLE; - blkbk->pending_pages[i] = alloc_page(GFP_KERNEL); - if (blkbk->pending_pages[i] == NULL) { - rc = -ENOMEM; - goto out_of_memory; - } } rc = xen_blkif_interface_init(); if (rc) @@ -1130,13 +1181,6 @@ static int __init xen_blkif_init(void) failed_init: kfree(blkbk->pending_reqs); kfree(blkbk->pending_grant_handles); - if (blkbk->pending_pages) { - for (i = 0; i < mmap_pages; i++) { - if (blkbk->pending_pages[i]) - __free_page(blkbk->pending_pages[i]); - } - kfree(blkbk->pending_pages); - } kfree(blkbk); blkbk = NULL; return rc; |