According to the interface comments, gnttab_end_foreign_access() is
supposed to free the page once the grant is no longer in use, from a
polling timer, but that was never implemented. Implement it.
This shouldn't make any real difference, because the existing drivers
all arrange that with well-behaved backends references are never ended
while they're still in use, but it tidies things up a bit.
Signed-off-by: Steven Smith <steven.smith@xxxxxxxxxx>
---
drivers/xen/grant-table.c | 103 +++++++++++++++++++++++++++++++++++++++++----
1 files changed, 94 insertions(+), 9 deletions(-)
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index cd82d22..52183aa 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -51,11 +51,17 @@
#define GNTTAB_LIST_END 0xffffffff
#define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))
+static void pending_free_timer(unsigned long ignore);
+
static grant_ref_t **gnttab_list;
static unsigned int nr_grant_frames;
static unsigned int boot_max_nr_grant_frames;
static int gnttab_free_count;
static grant_ref_t gnttab_free_head;
+static grant_ref_t gnttab_pending_free_gref_head = GNTTAB_LIST_END;
+static LIST_HEAD(gnttab_pending_free_pages);
+static DEFINE_TIMER(gnttab_delayed_free_timer, pending_free_timer, 0, 0);
+static DEFINE_SPINLOCK(gnttab_pending_free_lock);
static DEFINE_SPINLOCK(gnttab_list_lock);
static struct grant_entry *shared;
@@ -191,35 +197,114 @@ int gnttab_query_foreign_access(grant_ref_t ref)
}
EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
-int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
+static int _gnttab_end_foreign_access_ref(grant_ref_t ref)
{
u16 flags, nflags;
nflags = shared[ref].flags;
do {
flags = nflags;
- if (flags & (GTF_reading|GTF_writing)) {
- printk(KERN_ALERT "WARNING: g.e. still in use!\n");
+ if (flags & (GTF_reading|GTF_writing))
return 0;
- }
} while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) !=
flags);
return 1;
}
+
+int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
+{
+ int r;
+
+ r = _gnttab_end_foreign_access_ref(ref);
+ if (!r)
+ printk(KERN_ALERT "WARNING: g.e. still in use!\n");
+ return r;
+}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
+static void pending_free_timer(unsigned long ignore)
+{
+ grant_ref_t gref, next_gref;
+ grant_ref_t prev; /* The last gref which we failed to release,
+ or GNTTAB_LIST_END if there is no such
+ gref. */
+ int need_mod_timer;
+ struct page *page, *next_page;
+
+ spin_lock(&gnttab_pending_free_lock);
+ prev = GNTTAB_LIST_END;
+ for (gref = gnttab_pending_free_gref_head;
+ gref != GNTTAB_LIST_END;
+ gref = next_gref) {
+ next_gref = gnttab_entry(gref);
+ if (_gnttab_end_foreign_access_ref(gref)) {
+ put_free_entry(gref);
+ if (prev != GNTTAB_LIST_END)
+ gnttab_entry(prev) = next_gref;
+ else
+ gnttab_pending_free_gref_head = next_gref;
+ } else {
+ prev = gref;
+ }
+ }
+ list_for_each_entry_safe(page, next_page,
+ &gnttab_pending_free_pages, lru) {
+ gref = page->index;
+ if (_gnttab_end_foreign_access_ref(gref)) {
+ list_del(&page->lru);
+ put_free_entry(gref);
+ /* The page hasn't been used in this domain
+ for more than a second, so it's probably
+ cold. */
+ if (put_page_testzero(page)) {
+#ifdef MODULE
+ __free_page(page);
+#else
+ free_cold_page(page);
+#endif
+ }
+ }
+ }
+
+ need_mod_timer =
+ (gnttab_pending_free_gref_head != GNTTAB_LIST_END) ||
+ !list_empty(&gnttab_pending_free_pages);
+ spin_unlock(&gnttab_pending_free_lock);
+
+ if (need_mod_timer)
+ mod_timer(&gnttab_delayed_free_timer, jiffies + HZ);
+}
+
void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
unsigned long page)
{
- if (gnttab_end_foreign_access_ref(ref, readonly)) {
+ int need_mod_timer;
+ struct page *page_struct;
+
+ if (_gnttab_end_foreign_access_ref(ref)) {
put_free_entry(ref);
if (page != 0)
free_page(page);
} else {
- /* XXX This needs to be fixed so that the ref and page are
- placed on a list to be freed up later. */
- printk(KERN_WARNING
- "WARNING: leaking g.e. and page still in use!\n");
+ spin_lock_bh(&gnttab_pending_free_lock);
+ if (page == 0) {
+ if (gnttab_pending_free_gref_head == GNTTAB_LIST_END)
+ need_mod_timer = 1;
+ else
+ need_mod_timer = 0;
+ gnttab_entry(ref) = gnttab_pending_free_gref_head;
+ gnttab_pending_free_gref_head = ref;
+ } else {
+ need_mod_timer =
+ list_empty(&gnttab_pending_free_pages);
+ page_struct = virt_to_page((void *)page);
+ page_struct->index = ref;
+ list_add_tail(&page_struct->lru,
+ &gnttab_pending_free_pages);
+ }
+ spin_unlock_bh(&gnttab_pending_free_lock);
+ if (need_mod_timer)
+ mod_timer(&gnttab_delayed_free_timer, jiffies + HZ);
}
}
EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
--
1.6.3.1
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