Commit 7165092f authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

radix-tree,shmem: introduce radix_tree_iter_next() 



shmem likes to occasionally drop the lock, schedule, then reacqire the
lock and continue with the iteration from the last place it left off.
This is currently done with a pretty ugly goto.  Introduce
radix_tree_iter_next() and use it throughout shmem.c.

[koct9i@gmail.com: fix bug in radix_tree_iter_next() for tagged iteration]
Signed-off-by: default avatarMatthew Wilcox <willy@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarKonstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2cf938aa

include/linux/radix-tree.h

+16 −0
Original line number Diff line number Diff line
@@ -402,6 +402,22 @@ void **radix_tree_iter_retry(struct radix_tree_iter *iter) 
	return NULL;

}



/**

 * radix_tree_iter_next - resume iterating when the chunk may be invalid

 * @iter:	iterator state

 *

 * If the iterator needs to release then reacquire a lock, the chunk may

 * have been invalidated by an insertion or deletion.  Call this function

 * to continue the iteration from the next index.

 */

static inline __must_check

void **radix_tree_iter_next(struct radix_tree_iter *iter)

{

	iter->next_index = iter->index + 1;

	iter->tags = 0;

	return NULL;

}



/**

 * radix_tree_chunk_size - get current chunk size

 *

mm/shmem.c

+3 −9
Original line number Diff line number Diff line
@@ -376,7 +376,6 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping, 


	rcu_read_lock();



restart:

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

		if (iter.index >= end)

			break;
@@ -393,8 +392,7 @@ restart: 


		if (need_resched()) {

			cond_resched_rcu();

			start = iter.index + 1;

			goto restart;

			slot = radix_tree_iter_next(&iter);

		}

	}
@@ -1944,7 +1942,6 @@ static void shmem_tag_pins(struct address_space *mapping) 
	start = 0;

	rcu_read_lock();



restart:

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

		page = radix_tree_deref_slot(slot);

		if (!page || radix_tree_exception(page)) {
@@ -1961,8 +1958,7 @@ restart: 


		if (need_resched()) {

			cond_resched_rcu();

			start = iter.index + 1;

			goto restart;

			slot = radix_tree_iter_next(&iter);

		}

	}

	rcu_read_unlock();
@@ -1999,7 +1995,6 @@ static int shmem_wait_for_pins(struct address_space *mapping) 


		start = 0;

		rcu_read_lock();

restart:

		radix_tree_for_each_tagged(slot, &mapping->page_tree, &iter,

					   start, SHMEM_TAG_PINNED) {
@@ -2033,8 +2028,7 @@ restart: 
continue_resched:

			if (need_resched()) {

				cond_resched_rcu();

				start = iter.index + 1;

				goto restart;

				slot = radix_tree_iter_next(&iter);

			}

		}

		rcu_read_unlock();

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