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-rw-r--r--Documentation/ABI/stable/sysfs-bus-xen-backend8
-rw-r--r--drivers/block/xen-blkback/blkback.c286
-rw-r--r--drivers/block/xen-blkback/common.h5
-rw-r--r--drivers/block/xen-blkback/xenbus.c3
4 files changed, 181 insertions, 121 deletions
diff --git a/Documentation/ABI/stable/sysfs-bus-xen-backend b/Documentation/ABI/stable/sysfs-bus-xen-backend
index 3d5951c8bf5f..e04afe0cca99 100644
--- a/Documentation/ABI/stable/sysfs-bus-xen-backend
+++ b/Documentation/ABI/stable/sysfs-bus-xen-backend
@@ -73,3 +73,11 @@ KernelVersion: 3.0
Contact: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Description:
Number of sectors written by the frontend.
+
+What: /sys/module/xen_blkback/parameters/max_buffer_pages
+Date: March 2013
+KernelVersion: 3.10
+Contact: Roger Pau Monné <roger.pau@citrix.com>
+Description:
+ Maximum number of free pages to keep in each block
+ backend buffer.
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index f7526dbb204d..8245c6bb9539 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;
diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 60103e2517ba..6c73c3855e65 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -220,6 +220,11 @@ struct xen_blkif {
struct rb_root persistent_gnts;
unsigned int persistent_gnt_c;
+ /* buffer of free pages to map grant refs */
+ spinlock_t free_pages_lock;
+ int free_pages_num;
+ struct list_head free_pages;
+
/* statistics */
unsigned long st_print;
unsigned long long st_rd_req;
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index 8bfd1bcf95ec..24f7f6d87717 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -118,6 +118,9 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
blkif->st_print = jiffies;
init_waitqueue_head(&blkif->waiting_to_free);
blkif->persistent_gnts.rb_node = NULL;
+ spin_lock_init(&blkif->free_pages_lock);
+ INIT_LIST_HEAD(&blkif->free_pages);
+ blkif->free_pages_num = 0;
return blkif;
}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.