memfd: Convert memfd_wait_for_pins to XArray (2313216f) · Commits · 戴 / test

mm/memfd.c

+25 −36

Original line number	Diff line number	Diff line
		@@ -21,7 +21,7 @@
		#include <uapi/linux/memfd.h>

		/*
		* We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
		* We need a tag: a new tag would expand every xa_node by 8 bytes,
		* so reuse a tag which we firmly believe is never set or cleared on tmpfs
		* or hugetlbfs because they are memory only filesystems.
		*/
		@@ -72,9 +72,7 @@ static void memfd_tag_pins(struct address_space *mapping)
		*/
		static int memfd_wait_for_pins(struct address_space *mapping)
		{
		struct radix_tree_iter iter;
		void __rcu **slot;
		pgoff_t start;
		XA_STATE(xas, &mapping->i_pages, 0);
		struct page *page;
		int error, scan;

		@@ -82,7 +80,9 @@ static int memfd_wait_for_pins(struct address_space *mapping)

		error = 0;
		for (scan = 0; scan <= LAST_SCAN; scan++) {
		if (!radix_tree_tagged(&mapping->i_pages, MEMFD_TAG_PINNED))
		unsigned int tagged = 0;

		if (!xas_marked(&xas, MEMFD_TAG_PINNED))
		break;

		if (!scan)
		@@ -90,45 +90,34 @@ static int memfd_wait_for_pins(struct address_space *mapping)
		else if (schedule_timeout_killable((HZ << scan) / 200))
		scan = LAST_SCAN;

		start = 0;
		rcu_read_lock();
		radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter,
		start, MEMFD_TAG_PINNED) {

		page = radix_tree_deref_slot(slot);
		if (radix_tree_exception(page)) {
		if (radix_tree_deref_retry(page)) {
		slot = radix_tree_iter_retry(&iter);
		xas_set(&xas, 0);
		xas_lock_irq(&xas);
		xas_for_each_marked(&xas, page, ULONG_MAX, MEMFD_TAG_PINNED) {
		bool clear = true;
		if (xa_is_value(page))
		continue;
		}

		page = NULL;
		}

		if (page &&
		page_count(page) - page_mapcount(page) != 1) {
		if (scan < LAST_SCAN)
		goto continue_resched;

		if (page_count(page) - page_mapcount(page) != 1) {
		/*
		* On the last scan, we clean up all those tags
		* we inserted; but make a note that we still
		* found pages pinned.
		*/
		if (scan == LAST_SCAN)
		error = -EBUSY;
		else
		clear = false;
		}
		if (clear)
		xas_clear_mark(&xas, MEMFD_TAG_PINNED);
		if (++tagged % XA_CHECK_SCHED)
		continue;

		xa_lock_irq(&mapping->i_pages);
		radix_tree_tag_clear(&mapping->i_pages,
		iter.index, MEMFD_TAG_PINNED);
		xa_unlock_irq(&mapping->i_pages);
		continue_resched:
		if (need_resched()) {
		slot = radix_tree_iter_resume(slot, &iter);
		cond_resched_rcu();
		xas_pause(&xas);
		xas_unlock_irq(&xas);
		cond_resched();
		xas_lock_irq(&xas);
		}
		}
		rcu_read_unlock();
		xas_unlock_irq(&xas);
		}

		return error;

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