|
|
@@ -42,6 +42,75 @@ void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *pa
|
|
|
}
|
|
|
EXPORT_SYMBOL(__fscache_wait_on_page_write);
|
|
|
|
|
|
+/*
|
|
|
+ * decide whether a page can be released, possibly by cancelling a store to it
|
|
|
+ * - we're allowed to sleep if __GFP_WAIT is flagged
|
|
|
+ */
|
|
|
+bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
|
|
|
+ struct page *page,
|
|
|
+ gfp_t gfp)
|
|
|
+{
|
|
|
+ struct page *xpage;
|
|
|
+ void *val;
|
|
|
+
|
|
|
+ _enter("%p,%p,%x", cookie, page, gfp);
|
|
|
+
|
|
|
+ rcu_read_lock();
|
|
|
+ val = radix_tree_lookup(&cookie->stores, page->index);
|
|
|
+ if (!val) {
|
|
|
+ rcu_read_unlock();
|
|
|
+ fscache_stat(&fscache_n_store_vmscan_not_storing);
|
|
|
+ __fscache_uncache_page(cookie, page);
|
|
|
+ return true;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* see if the page is actually undergoing storage - if so we can't get
|
|
|
+ * rid of it till the cache has finished with it */
|
|
|
+ if (radix_tree_tag_get(&cookie->stores, page->index,
|
|
|
+ FSCACHE_COOKIE_STORING_TAG)) {
|
|
|
+ rcu_read_unlock();
|
|
|
+ goto page_busy;
|
|
|
+ }
|
|
|
+
|
|
|
+ /* the page is pending storage, so we attempt to cancel the store and
|
|
|
+ * discard the store request so that the page can be reclaimed */
|
|
|
+ spin_lock(&cookie->stores_lock);
|
|
|
+ rcu_read_unlock();
|
|
|
+
|
|
|
+ if (radix_tree_tag_get(&cookie->stores, page->index,
|
|
|
+ FSCACHE_COOKIE_STORING_TAG)) {
|
|
|
+ /* the page started to undergo storage whilst we were looking,
|
|
|
+ * so now we can only wait or return */
|
|
|
+ spin_unlock(&cookie->stores_lock);
|
|
|
+ goto page_busy;
|
|
|
+ }
|
|
|
+
|
|
|
+ xpage = radix_tree_delete(&cookie->stores, page->index);
|
|
|
+ spin_unlock(&cookie->stores_lock);
|
|
|
+
|
|
|
+ if (xpage) {
|
|
|
+ fscache_stat(&fscache_n_store_vmscan_cancelled);
|
|
|
+ fscache_stat(&fscache_n_store_radix_deletes);
|
|
|
+ ASSERTCMP(xpage, ==, page);
|
|
|
+ } else {
|
|
|
+ fscache_stat(&fscache_n_store_vmscan_gone);
|
|
|
+ }
|
|
|
+
|
|
|
+ wake_up_bit(&cookie->flags, 0);
|
|
|
+ if (xpage)
|
|
|
+ page_cache_release(xpage);
|
|
|
+ __fscache_uncache_page(cookie, page);
|
|
|
+ return true;
|
|
|
+
|
|
|
+page_busy:
|
|
|
+ /* we might want to wait here, but that could deadlock the allocator as
|
|
|
+ * the slow-work threads writing to the cache may all end up sleeping
|
|
|
+ * on memory allocation */
|
|
|
+ fscache_stat(&fscache_n_store_vmscan_busy);
|
|
|
+ return false;
|
|
|
+}
|
|
|
+EXPORT_SYMBOL(__fscache_maybe_release_page);
|
|
|
+
|
|
|
/*
|
|
|
* note that a page has finished being written to the cache
|
|
|
*/
|
|
|
@@ -57,6 +126,8 @@ static void fscache_end_page_write(struct fscache_object *object,
|
|
|
/* delete the page from the tree if it is now no longer
|
|
|
* pending */
|
|
|
spin_lock(&cookie->stores_lock);
|
|
|
+ radix_tree_tag_clear(&cookie->stores, page->index,
|
|
|
+ FSCACHE_COOKIE_STORING_TAG);
|
|
|
if (!radix_tree_tag_get(&cookie->stores, page->index,
|
|
|
FSCACHE_COOKIE_PENDING_TAG)) {
|
|
|
fscache_stat(&fscache_n_store_radix_deletes);
|
|
|
@@ -640,8 +711,12 @@ static void fscache_write_op(struct fscache_operation *_op)
|
|
|
goto superseded;
|
|
|
}
|
|
|
|
|
|
- radix_tree_tag_clear(&cookie->stores, page->index,
|
|
|
- FSCACHE_COOKIE_PENDING_TAG);
|
|
|
+ if (page) {
|
|
|
+ radix_tree_tag_set(&cookie->stores, page->index,
|
|
|
+ FSCACHE_COOKIE_STORING_TAG);
|
|
|
+ radix_tree_tag_clear(&cookie->stores, page->index,
|
|
|
+ FSCACHE_COOKIE_PENDING_TAG);
|
|
|
+ }
|
|
|
|
|
|
spin_unlock(&cookie->stores_lock);
|
|
|
spin_unlock(&object->lock);
|
David Howells