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Date: Mon, 7 Dec 2020 14:30:23 +0100
From: Juergen Gross <jgross@...e.com>
To: xen-devel@...ts.xenproject.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org
Cc: Juergen Gross <jgross@...e.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
Roger Pau Monné <roger.pau@...rix.com>,
Jens Axboe <axboe@...nel.dk>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Stefano Stabellini <sstabellini@...nel.org>
Subject: [PATCH 1/2] xen: add helpers for caching grant mapping pages
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.
Signed-off-by: Juergen Gross <jgross@...e.com>
---
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(-)
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 501e9dacfff9..9ebf53903d7b 100644
--- 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 xen_blkif_ring *ring, struct rb_root *ro
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(struct work_struct *work)
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(struct work_struct *work)
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 @@ int xen_blkif_schedule(void *arg)
/* 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_blkif_ring *ring)
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_callback(int result, struct gntab_unmap_
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_blkif_ring *ring,
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 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
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 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
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 @@ static int xen_blkbk_map(struct xen_blkif_ring *ring,
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;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index c6ea5d38c509..a1b9df2c4ef1 100644
--- 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. */
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index f5705569e2a7..76912c584a76 100644
--- 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 xen_blkif *blkif)
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 xen_blkif *blkif)
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;
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 523dcdf39cc9..e2e42912f241 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -813,6 +813,78 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
}
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;
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 4acc4e899600..862162dca33c 100644
--- 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, scsiback_max_buffer_pages, int, 0644);
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_info *info)
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(struct vscsibk_pend *req)
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_pend *pending_req,
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 vscsibk_info *info,
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_device *dev)
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_device *dev,
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 @@ static int __init scsiback_init(void)
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);
}
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index 9bc5bc07d4d3..c6ef8ffc1a09 100644
--- 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. */
--
2.26.2
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