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xen-blkfront: pre-allocate pages for requests

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This prevents us from having to call alloc_page while we are preparing
the request. Since blkfront was calling alloc_page with a spinlock
held we used GFP_ATOMIC, which can fail if we are requesting a lot of
pages since it is using the emergency memory pools.

Allocating all the pages at init prevents us from having to call
alloc_page, thus preventing possible failures.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: xen-devel@lists.xen.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Roger Pau Monne 2013-03-18 17:49:35 +01:00 committed by Konrad Rzeszutek Wilk
parent ffb1dabd1e
commit 9c1e050cae
1 changed files with 79 additions and 41 deletions
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120
drivers/block/xen-blkfront.c
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@ -165,6 +165,69 @@ static int add_id_to_freelist(struct blkfront_info *info,
return 0;
}
static int fill_grant_buffer(struct blkfront_info *info, int num)
{
struct page *granted_page;
struct grant *gnt_list_entry, *n;
int i = 0;
while(i < num) {
gnt_list_entry = kzalloc(sizeof(struct grant), GFP_NOIO);
if (!gnt_list_entry)
goto out_of_memory;
granted_page = alloc_page(GFP_NOIO);
if (!granted_page) {
kfree(gnt_list_entry);
goto out_of_memory;
}
gnt_list_entry->pfn = page_to_pfn(granted_page);
gnt_list_entry->gref = GRANT_INVALID_REF;
list_add(&gnt_list_entry->node, &info->persistent_gnts);
i++;
}
return 0;
out_of_memory:
list_for_each_entry_safe(gnt_list_entry, n,
&info->persistent_gnts, node) {
list_del(&gnt_list_entry->node);
__free_page(pfn_to_page(gnt_list_entry->pfn));
kfree(gnt_list_entry);
i--;
}
BUG_ON(i != 0);
return -ENOMEM;
}
static struct grant *get_grant(grant_ref_t *gref_head,
struct blkfront_info *info)
{
struct grant *gnt_list_entry;
unsigned long buffer_mfn;
BUG_ON(list_empty(&info->persistent_gnts));
gnt_list_entry = list_first_entry(&info->persistent_gnts, struct grant,
node);
list_del(&gnt_list_entry->node);
if (gnt_list_entry->gref != GRANT_INVALID_REF) {
info->persistent_gnts_c--;
return gnt_list_entry;
}
/* Assign a gref to this page */
gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
BUG_ON(gnt_list_entry->gref == -ENOSPC);
buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
gnttab_grant_foreign_access_ref(gnt_list_entry->gref,
info->xbdev->otherend_id,
buffer_mfn, 0);
return gnt_list_entry;
}
static const char *op_name(int op)
{
static const char *const names[] = {
@ -306,7 +369,6 @@ static int blkif_queue_request(struct request *req)
*/
bool new_persistent_gnts;
grant_ref_t gref_head;
struct page *granted_page;
struct grant *gnt_list_entry = NULL;
struct scatterlist *sg;
@ -370,42 +432,9 @@ static int blkif_queue_request(struct request *req)
fsect = sg->offset >> 9;
lsect = fsect + (sg->length >> 9) - 1;
if (info->persistent_gnts_c) {
BUG_ON(list_empty(&info->persistent_gnts));
gnt_list_entry = list_first_entry(
&info->persistent_gnts,
struct grant, node);
list_del(&gnt_list_entry->node);
ref = gnt_list_entry->gref;
buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
info->persistent_gnts_c--;
} else {
ref = gnttab_claim_grant_reference(&gref_head);
BUG_ON(ref == -ENOSPC);
gnt_list_entry =
kmalloc(sizeof(struct grant),
GFP_ATOMIC);
if (!gnt_list_entry)
return -ENOMEM;
granted_page = alloc_page(GFP_ATOMIC);
if (!granted_page) {
kfree(gnt_list_entry);
return -ENOMEM;
}
gnt_list_entry->pfn =
page_to_pfn(granted_page);
gnt_list_entry->gref = ref;
buffer_mfn = pfn_to_mfn(page_to_pfn(
granted_page));
gnttab_grant_foreign_access_ref(ref,
info->xbdev->otherend_id,
buffer_mfn, 0);
}
gnt_list_entry = get_grant(&gref_head, info);
ref = gnt_list_entry->gref;
buffer_mfn = pfn_to_mfn(gnt_list_entry->pfn);
info->shadow[id].grants_used[i] = gnt_list_entry;
@ -803,17 +832,20 @@ static void blkif_free(struct blkfront_info *info, int suspend)
blk_stop_queue(info->rq);
/* Remove all persistent grants */
if (info->persistent_gnts_c) {
if (!list_empty(&info->persistent_gnts)) {
list_for_each_entry_safe(persistent_gnt, n,
&info->persistent_gnts, node) {
list_del(&persistent_gnt->node);
gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
if (persistent_gnt->gref != GRANT_INVALID_REF) {
gnttab_end_foreign_access(persistent_gnt->gref,
0, 0UL);
info->persistent_gnts_c--;
}
__free_page(pfn_to_page(persistent_gnt->pfn));
kfree(persistent_gnt);
info->persistent_gnts_c--;
}
BUG_ON(info->persistent_gnts_c != 0);
}
BUG_ON(info->persistent_gnts_c != 0);
/* No more gnttab callback work. */
gnttab_cancel_free_callback(&info->callback);
@ -1008,6 +1040,12 @@ static int setup_blkring(struct xenbus_device *dev,
sg_init_table(info->sg, BLKIF_MAX_SEGMENTS_PER_REQUEST);
/* Allocate memory for grants */
err = fill_grant_buffer(info, BLK_RING_SIZE *
BLKIF_MAX_SEGMENTS_PER_REQUEST);
if (err)
goto fail;
err = xenbus_grant_ring(dev, virt_to_mfn(info->ring.sring));
if (err < 0) {
free_page((unsigned long)sring);