Commit 2cf938aa authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

mm: use radix_tree_iter_retry() 



Instead of a 'goto restart', we can now use radix_tree_iter_retry() to
restart from our current position.  This will make a difference when
there are more ways to happen across an indirect pointer.  And it
eliminates some confusing gotos.

[vbabka@suse.cz: remove now-obsolete-and-misleading comment]
Signed-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c28f2420

mm/filemap.c

+17 −36
Original line number Diff line number Diff line
@@ -1255,7 +1255,6 @@ unsigned find_get_entries(struct address_space *mapping, 
		return 0;



	rcu_read_lock();

restart:

	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {

		struct page *page;

repeat:
@@ -1263,8 +1262,10 @@ repeat: 
		if (unlikely(!page))

			continue;

		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page))

				goto restart;

			if (radix_tree_deref_retry(page)) {

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

			/*

			 * A shadow entry of a recently evicted page, a swap

			 * entry from shmem/tmpfs or a DAX entry.  Return it
@@ -1317,7 +1318,6 @@ unsigned find_get_pages(struct address_space *mapping, pgoff_t start, 
		return 0;



	rcu_read_lock();

restart:

	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {

		struct page *page;

repeat:
@@ -1327,13 +1327,8 @@ repeat: 


		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page)) {

				/*

				 * Transient condition which can only trigger

				 * when entry at index 0 moves out of or back

				 * to root: none yet gotten, safe to restart.

				 */

				WARN_ON(iter.index);

				goto restart;

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

			/*

			 * A shadow entry of a recently evicted page,
@@ -1384,7 +1379,6 @@ unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, 
		return 0;



	rcu_read_lock();

restart:

	radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {

		struct page *page;

repeat:
@@ -1395,12 +1389,8 @@ repeat: 


		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page)) {

				/*

				 * Transient condition which can only trigger

				 * when entry at index 0 moves out of or back

				 * to root: none yet gotten, safe to restart.

				 */

				goto restart;

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

			/*

			 * A shadow entry of a recently evicted page,
@@ -1460,7 +1450,6 @@ unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, 
		return 0;



	rcu_read_lock();

restart:

	radix_tree_for_each_tagged(slot, &mapping->page_tree,

				   &iter, *index, tag) {

		struct page *page;
@@ -1471,12 +1460,8 @@ repeat: 


		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page)) {

				/*

				 * Transient condition which can only trigger

				 * when entry at index 0 moves out of or back

				 * to root: none yet gotten, safe to restart.

				 */

				goto restart;

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

			/*

			 * A shadow entry of a recently evicted page.
@@ -1539,7 +1524,6 @@ unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start, 
		return 0;



	rcu_read_lock();

restart:

	radix_tree_for_each_tagged(slot, &mapping->page_tree,

				   &iter, start, tag) {

		struct page *page;
@@ -1549,12 +1533,8 @@ repeat: 
			continue;

		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page)) {

				/*

				 * Transient condition which can only trigger

				 * when entry at index 0 moves out of or back

				 * to root: none yet gotten, safe to restart.

				 */

				goto restart;

				slot = radix_tree_iter_retry(&iter);

				continue;

			}



			/*
@@ -2171,9 +2151,10 @@ repeat: 
		if (unlikely(!page))

			goto next;

		if (radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page))

				break;

			else

			if (radix_tree_deref_retry(page)) {

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

			goto next;

		}

mm/shmem.c

+12 −11
Original line number Diff line number Diff line
@@ -383,13 +383,10 @@ restart: 


		page = radix_tree_deref_slot(slot);



		/*

		 * This should only be possible to happen at index 0, so we

		 * don't need to reset the counter, nor do we risk infinite

		 * restarts.

		 */

		if (radix_tree_deref_retry(page))

			goto restart;

		if (radix_tree_deref_retry(page)) {

			slot = radix_tree_iter_retry(&iter);

			continue;

		}



		if (radix_tree_exceptional_entry(page))

			swapped++;
@@ -1951,8 +1948,10 @@ restart: 
	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {

		page = radix_tree_deref_slot(slot);

		if (!page || radix_tree_exception(page)) {

			if (radix_tree_deref_retry(page))

				goto restart;

			if (radix_tree_deref_retry(page)) {

				slot = radix_tree_iter_retry(&iter);

				continue;

			}

		} else if (page_count(page) - page_mapcount(page) > 1) {

			spin_lock_irq(&mapping->tree_lock);

			radix_tree_tag_set(&mapping->page_tree, iter.index,
@@ -2006,8 +2005,10 @@ restart: 


			page = radix_tree_deref_slot(slot);

			if (radix_tree_exception(page)) {

				if (radix_tree_deref_retry(page))

					goto restart;

				if (radix_tree_deref_retry(page)) {

					slot = radix_tree_iter_retry(&iter);

					continue;

				}



				page = NULL;

			}

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