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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.

Cc: <stable@vger.kernel.org> # 5.9
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovksy@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Juergen Gross 2020-12-07 08:31:22 +01:00
parent a68a0262ab
commit ca33479cc7
6 changed files with 116 additions and 128 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
drivers/block/xen-blkback/blkback.c
View File

@ -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 @@ 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_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 @@ 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;

4
drivers/block/xen-blkback/common.h
View File

@ -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. */

6
drivers/block/xen-blkback/xenbus.c
View File

@ -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;

72
drivers/xen/grant-table.c
View File

@ -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;

60
drivers/xen/xen-scsiback.c
View File

@ -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 @@ 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);
}

13
include/xen/grant_table.h
View File

@ -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. */