From 7165092fe5ca70bae722ac6cd78421cfd0eec18d Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Thu, 17 Mar 2016 14:22:06 -0700 Subject: [PATCH] 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: Matthew Wilcox Cc: Hugh Dickins Signed-off-by: Konstantin Khlebnikov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/radix-tree.h | 16 ++++++++++++++++ mm/shmem.c | 12 +++--------- 2 files changed, 19 insertions(+), 9 deletions(-) diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h index b211f145c811..51a97ac8bfbf 100644 --- a/include/linux/radix-tree.h +++ b/include/linux/radix-tree.h @@ -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 * diff --git a/mm/shmem.c b/mm/shmem.c index 91c0dadf48d3..9428c51ab2d6 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -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 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping, 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 @@ static void shmem_tag_pins(struct address_space *mapping) 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 @@ static int shmem_wait_for_pins(struct address_space *mapping) continue_resched: if (need_resched()) { cond_resched_rcu(); - start = iter.index + 1; - goto restart; + slot = radix_tree_iter_next(&iter); } } rcu_read_unlock(); -- 2.45.2