This is a note to let you know that I've just added the patch titled xen: add helpers for caching grant mapping pages to the 5.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: xen-add-helpers-for-caching-grant-mapping-pages.patch and it can be found in the queue-5.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From ca33479cc7be2c9b5f8be078c8bf3ac26b7d6186 Mon Sep 17 00:00:00 2001 From: Juergen Gross <jgross@xxxxxxxx> Date: Mon, 7 Dec 2020 08:31:22 +0100 Subject: xen: add helpers for caching grant mapping pages From: Juergen Gross <jgross@xxxxxxxx> commit ca33479cc7be2c9b5f8be078c8bf3ac26b7d6186 upstream. Instead of having similar helpers in multiple backend drivers use common helpers for caching pages allocated via gnttab_alloc_pages(). Make use of those helpers in blkback and scsiback. Cc: <stable@xxxxxxxxxxxxxxx> # 5.9 Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Reviewed-by: Boris Ostrovsky <boris.ostrovksy@xxxxxxxxxx> Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/block/xen-blkback/blkback.c | 89 ++++++------------------------------ drivers/block/xen-blkback/common.h | 4 - drivers/block/xen-blkback/xenbus.c | 6 -- drivers/xen/grant-table.c | 72 +++++++++++++++++++++++++++++ drivers/xen/xen-scsiback.c | 60 ++++-------------------- include/xen/grant_table.h | 13 +++++ 6 files changed, 116 insertions(+), 128 deletions(-) --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -132,73 +132,12 @@ module_param(log_stats, int, 0644); #define BLKBACK_INVALID_HANDLE (~0) -/* Number of free pages to remove on each call to gnttab_free_pages */ -#define NUM_BATCH_FREE_PAGES 10 - static inline bool persistent_gnt_timeout(struct persistent_gnt *persistent_gnt) { return pgrant_timeout && (jiffies - persistent_gnt->last_used >= HZ * pgrant_timeout); } -static inline int get_free_page(struct xen_blkif_ring *ring, struct page **page) -{ - unsigned long flags; - - spin_lock_irqsave(&ring->free_pages_lock, flags); - if (list_empty(&ring->free_pages)) { - BUG_ON(ring->free_pages_num != 0); - spin_unlock_irqrestore(&ring->free_pages_lock, flags); - return gnttab_alloc_pages(1, page); - } - BUG_ON(ring->free_pages_num == 0); - page[0] = list_first_entry(&ring->free_pages, struct page, lru); - list_del(&page[0]->lru); - ring->free_pages_num--; - spin_unlock_irqrestore(&ring->free_pages_lock, flags); - - return 0; -} - -static inline void put_free_pages(struct xen_blkif_ring *ring, struct page **page, - int num) -{ - unsigned long flags; - int i; - - spin_lock_irqsave(&ring->free_pages_lock, flags); - for (i = 0; i < num; i++) - 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_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(&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); - ring->free_pages_num--; - if (++num_pages == NUM_BATCH_FREE_PAGES) { - spin_unlock_irqrestore(&ring->free_pages_lock, flags); - gnttab_free_pages(num_pages, page); - spin_lock_irqsave(&ring->free_pages_lock, flags); - num_pages = 0; - } - } - 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_ring *ring, unsigned int *eoi_flags); @@ -331,7 +270,8 @@ static void free_persistent_gnts(struct unmap_data.count = segs_to_unmap; BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); - put_free_pages(ring, pages, segs_to_unmap); + gnttab_page_cache_put(&ring->free_pages, pages, + segs_to_unmap); segs_to_unmap = 0; } @@ -371,7 +311,8 @@ void xen_blkbk_unmap_purged_grants(struc if (++segs_to_unmap == BLKIF_MAX_SEGMENTS_PER_REQUEST) { unmap_data.count = segs_to_unmap; BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); - put_free_pages(ring, pages, segs_to_unmap); + gnttab_page_cache_put(&ring->free_pages, pages, + segs_to_unmap); segs_to_unmap = 0; } kfree(persistent_gnt); @@ -379,7 +320,7 @@ void xen_blkbk_unmap_purged_grants(struc if (segs_to_unmap > 0) { unmap_data.count = segs_to_unmap; BUG_ON(gnttab_unmap_refs_sync(&unmap_data)); - put_free_pages(ring, pages, segs_to_unmap); + gnttab_page_cache_put(&ring->free_pages, pages, segs_to_unmap); } } @@ -664,9 +605,10 @@ purge_gnt_list: /* Shrink the free pages pool if it is too large. */ if (time_before(jiffies, blkif->buffer_squeeze_end)) - shrink_free_pagepool(ring, 0); + gnttab_page_cache_shrink(&ring->free_pages, 0); else - shrink_free_pagepool(ring, max_buffer_pages); + gnttab_page_cache_shrink(&ring->free_pages, + max_buffer_pages); if (log_stats && time_after(jiffies, ring->st_print)) print_stats(ring); @@ -697,7 +639,7 @@ void xen_blkbk_free_caches(struct xen_bl ring->persistent_gnt_c = 0; /* Since we are shutting down remove all pages from the buffer */ - shrink_free_pagepool(ring, 0 /* All */); + gnttab_page_cache_shrink(&ring->free_pages, 0 /* All */); } static unsigned int xen_blkbk_unmap_prepare( @@ -736,7 +678,7 @@ static void xen_blkbk_unmap_and_respond_ but is this the best way to deal with this? */ BUG_ON(result); - put_free_pages(ring, data->pages, data->count); + gnttab_page_cache_put(&ring->free_pages, data->pages, data->count); make_response(ring, pending_req->id, pending_req->operation, pending_req->status); free_req(ring, pending_req); @@ -803,7 +745,8 @@ static void xen_blkbk_unmap(struct xen_b if (invcount) { ret = gnttab_unmap_refs(unmap, NULL, unmap_pages, invcount); BUG_ON(ret); - put_free_pages(ring, unmap_pages, invcount); + gnttab_page_cache_put(&ring->free_pages, unmap_pages, + invcount); } pages += batch; num -= batch; @@ -850,7 +793,8 @@ again: pages[i]->page = persistent_gnt->page; pages[i]->persistent_gnt = persistent_gnt; } else { - if (get_free_page(ring, &pages[i]->page)) + if (gnttab_page_cache_get(&ring->free_pages, + &pages[i]->page)) goto out_of_memory; addr = vaddr(pages[i]->page); pages_to_gnt[segs_to_map] = pages[i]->page; @@ -883,7 +827,8 @@ again: BUG_ON(new_map_idx >= segs_to_map); if (unlikely(map[new_map_idx].status != 0)) { pr_debug("invalid buffer -- could not remap it\n"); - put_free_pages(ring, &pages[seg_idx]->page, 1); + gnttab_page_cache_put(&ring->free_pages, + &pages[seg_idx]->page, 1); pages[seg_idx]->handle = BLKBACK_INVALID_HANDLE; ret |= 1; goto next; @@ -944,7 +889,7 @@ next: out_of_memory: pr_alert("%s: out of memory\n", __func__); - put_free_pages(ring, pages_to_gnt, segs_to_map); + gnttab_page_cache_put(&ring->free_pages, pages_to_gnt, segs_to_map); for (i = last_map; i < num; i++) pages[i]->handle = BLKBACK_INVALID_HANDLE; return -ENOMEM; --- a/drivers/block/xen-blkback/common.h +++ b/drivers/block/xen-blkback/common.h @@ -288,9 +288,7 @@ struct xen_blkif_ring { struct work_struct persistent_purge_work; /* Buffer of free pages to map grant refs. */ - spinlock_t free_pages_lock; - int free_pages_num; - struct list_head free_pages; + struct gnttab_page_cache free_pages; struct work_struct free_work; /* Thread shutdown wait queue. */ --- a/drivers/block/xen-blkback/xenbus.c +++ b/drivers/block/xen-blkback/xenbus.c @@ -144,8 +144,7 @@ static int xen_blkif_alloc_rings(struct INIT_LIST_HEAD(&ring->pending_free); INIT_LIST_HEAD(&ring->persistent_purge_list); INIT_WORK(&ring->persistent_purge_work, xen_blkbk_unmap_purged_grants); - spin_lock_init(&ring->free_pages_lock); - INIT_LIST_HEAD(&ring->free_pages); + gnttab_page_cache_init(&ring->free_pages); spin_lock_init(&ring->pending_free_lock); init_waitqueue_head(&ring->pending_free_wq); @@ -317,8 +316,7 @@ static int xen_blkif_disconnect(struct x BUG_ON(atomic_read(&ring->persistent_gnt_in_use) != 0); BUG_ON(!list_empty(&ring->persistent_purge_list)); BUG_ON(!RB_EMPTY_ROOT(&ring->persistent_gnts)); - BUG_ON(!list_empty(&ring->free_pages)); - BUG_ON(ring->free_pages_num != 0); + BUG_ON(ring->free_pages.num_pages != 0); BUG_ON(ring->persistent_gnt_c != 0); WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages)); ring->active = false; --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -813,6 +813,78 @@ int gnttab_alloc_pages(int nr_pages, str } EXPORT_SYMBOL_GPL(gnttab_alloc_pages); +void gnttab_page_cache_init(struct gnttab_page_cache *cache) +{ + spin_lock_init(&cache->lock); + INIT_LIST_HEAD(&cache->pages); + cache->num_pages = 0; +} +EXPORT_SYMBOL_GPL(gnttab_page_cache_init); + +int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page) +{ + unsigned long flags; + + spin_lock_irqsave(&cache->lock, flags); + + if (list_empty(&cache->pages)) { + spin_unlock_irqrestore(&cache->lock, flags); + return gnttab_alloc_pages(1, page); + } + + page[0] = list_first_entry(&cache->pages, struct page, lru); + list_del(&page[0]->lru); + cache->num_pages--; + + spin_unlock_irqrestore(&cache->lock, flags); + + return 0; +} +EXPORT_SYMBOL_GPL(gnttab_page_cache_get); + +void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page, + unsigned int num) +{ + unsigned long flags; + unsigned int i; + + spin_lock_irqsave(&cache->lock, flags); + + for (i = 0; i < num; i++) + list_add(&page[i]->lru, &cache->pages); + cache->num_pages += num; + + spin_unlock_irqrestore(&cache->lock, flags); +} +EXPORT_SYMBOL_GPL(gnttab_page_cache_put); + +void gnttab_page_cache_shrink(struct gnttab_page_cache *cache, unsigned int num) +{ + struct page *page[10]; + unsigned int i = 0; + unsigned long flags; + + spin_lock_irqsave(&cache->lock, flags); + + while (cache->num_pages > num) { + page[i] = list_first_entry(&cache->pages, struct page, lru); + list_del(&page[i]->lru); + cache->num_pages--; + if (++i == ARRAY_SIZE(page)) { + spin_unlock_irqrestore(&cache->lock, flags); + gnttab_free_pages(i, page); + i = 0; + spin_lock_irqsave(&cache->lock, flags); + } + } + + spin_unlock_irqrestore(&cache->lock, flags); + + if (i != 0) + gnttab_free_pages(i, page); +} +EXPORT_SYMBOL_GPL(gnttab_page_cache_shrink); + void gnttab_pages_clear_private(int nr_pages, struct page **pages) { int i; --- a/drivers/xen/xen-scsiback.c +++ b/drivers/xen/xen-scsiback.c @@ -99,6 +99,8 @@ struct vscsibk_info { struct list_head v2p_entry_lists; wait_queue_head_t waiting_to_free; + + struct gnttab_page_cache free_pages; }; /* theoretical maximum of grants for one request */ @@ -188,10 +190,6 @@ module_param_named(max_buffer_pages, scs MODULE_PARM_DESC(max_buffer_pages, "Maximum number of free pages to keep in backend buffer"); -static DEFINE_SPINLOCK(free_pages_lock); -static int free_pages_num; -static LIST_HEAD(scsiback_free_pages); - /* Global spinlock to protect scsiback TPG list */ static DEFINE_MUTEX(scsiback_mutex); static LIST_HEAD(scsiback_list); @@ -207,41 +205,6 @@ static void scsiback_put(struct vscsibk_ wake_up(&info->waiting_to_free); } -static void put_free_pages(struct page **page, int num) -{ - unsigned long flags; - int i = free_pages_num + num, n = num; - - if (num == 0) - return; - if (i > scsiback_max_buffer_pages) { - n = min(num, i - scsiback_max_buffer_pages); - gnttab_free_pages(n, page + num - n); - n = num - n; - } - spin_lock_irqsave(&free_pages_lock, flags); - for (i = 0; i < n; i++) - list_add(&page[i]->lru, &scsiback_free_pages); - free_pages_num += n; - spin_unlock_irqrestore(&free_pages_lock, flags); -} - -static int get_free_page(struct page **page) -{ - unsigned long flags; - - spin_lock_irqsave(&free_pages_lock, flags); - if (list_empty(&scsiback_free_pages)) { - spin_unlock_irqrestore(&free_pages_lock, flags); - return gnttab_alloc_pages(1, page); - } - page[0] = list_first_entry(&scsiback_free_pages, struct page, lru); - list_del(&page[0]->lru); - free_pages_num--; - spin_unlock_irqrestore(&free_pages_lock, flags); - return 0; -} - static unsigned long vaddr_page(struct page *page) { unsigned long pfn = page_to_pfn(page); @@ -302,7 +265,8 @@ static void scsiback_fast_flush_area(str BUG_ON(err); } - put_free_pages(req->pages, req->n_grants); + gnttab_page_cache_put(&req->info->free_pages, req->pages, + req->n_grants); req->n_grants = 0; } @@ -445,8 +409,8 @@ static int scsiback_gnttab_data_map_list struct vscsibk_info *info = pending_req->info; for (i = 0; i < cnt; i++) { - if (get_free_page(pg + mapcount)) { - put_free_pages(pg, mapcount); + if (gnttab_page_cache_get(&info->free_pages, pg + mapcount)) { + gnttab_page_cache_put(&info->free_pages, pg, mapcount); pr_err("no grant page\n"); return -ENOMEM; } @@ -796,6 +760,8 @@ static int scsiback_do_cmd_fn(struct vsc cond_resched(); } + gnttab_page_cache_shrink(&info->free_pages, scsiback_max_buffer_pages); + RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do); return more_to_do; } @@ -1233,6 +1199,8 @@ static int scsiback_remove(struct xenbus scsiback_release_translation_entry(info); + gnttab_page_cache_shrink(&info->free_pages, 0); + dev_set_drvdata(&dev->dev, NULL); return 0; @@ -1263,6 +1231,7 @@ static int scsiback_probe(struct xenbus_ info->irq = 0; INIT_LIST_HEAD(&info->v2p_entry_lists); spin_lock_init(&info->v2p_lock); + gnttab_page_cache_init(&info->free_pages); err = xenbus_printf(XBT_NIL, dev->nodename, "feature-sg-grant", "%u", SG_ALL); @@ -1879,13 +1848,6 @@ out: static void __exit scsiback_exit(void) { - struct page *page; - - while (free_pages_num) { - if (get_free_page(&page)) - BUG(); - gnttab_free_pages(1, &page); - } target_unregister_template(&scsiback_ops); xenbus_unregister_driver(&scsiback_driver); } --- a/include/xen/grant_table.h +++ b/include/xen/grant_table.h @@ -198,6 +198,19 @@ void gnttab_free_auto_xlat_frames(void); int gnttab_alloc_pages(int nr_pages, struct page **pages); void gnttab_free_pages(int nr_pages, struct page **pages); +struct gnttab_page_cache { + spinlock_t lock; + struct list_head pages; + unsigned int num_pages; +}; + +void gnttab_page_cache_init(struct gnttab_page_cache *cache); +int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page); +void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page, + unsigned int num); +void gnttab_page_cache_shrink(struct gnttab_page_cache *cache, + unsigned int num); + #ifdef CONFIG_XEN_GRANT_DMA_ALLOC struct gnttab_dma_alloc_args { /* Device for which DMA memory will be/was allocated. */ Patches currently in stable-queue which might be from jgross@xxxxxxxx are queue-5.9/xen-add-helpers-for-caching-grant-mapping-pages.patch queue-5.9/xen-don-t-use-page-lru-for-zone_device-memory.patch