From 6d3b050efa079f5bc4d5e2a8f37f0dc0345a2096 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Thu, 3 Feb 2022 15:36:45 +0000 Subject: [PATCH] btrfs: assert we have a write lock when removing and replacing extent maps Removing or replacing an extent map requires holding a write lock on the extent map's tree. We currently do that everywhere, except in one of the self tests, where it's harmless since there's no concurrency. In order to catch possible races in the future, assert that we are holding a write lock on the extent map tree before removing or replacing an extent map in the tree, and update the self test to obtain a write lock before removing extent maps. Reviewed-by: Johannes Thumshirn Signed-off-by: Filipe Manana Signed-off-by: David Sterba --- fs/btrfs/extent_map.c | 4 ++++ fs/btrfs/tests/extent-map-tests.c | 2 ++ 2 files changed, 6 insertions(+) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index c28ceddefae4..6fee14ce2e6b 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -492,6 +492,8 @@ struct extent_map *search_extent_mapping(struct extent_map_tree *tree, */ void remove_extent_mapping(struct extent_map_tree *tree, struct extent_map *em) { + lockdep_assert_held_write(&tree->lock); + WARN_ON(test_bit(EXTENT_FLAG_PINNED, &em->flags)); rb_erase_cached(&em->rb_node, &tree->map); if (!test_bit(EXTENT_FLAG_LOGGING, &em->flags)) @@ -506,6 +508,8 @@ void replace_extent_mapping(struct extent_map_tree *tree, struct extent_map *new, int modified) { + lockdep_assert_held_write(&tree->lock); + WARN_ON(test_bit(EXTENT_FLAG_PINNED, &cur->flags)); ASSERT(extent_map_in_tree(cur)); if (!test_bit(EXTENT_FLAG_LOGGING, &cur->flags)) diff --git a/fs/btrfs/tests/extent-map-tests.c b/fs/btrfs/tests/extent-map-tests.c index 319fed82d741..c5b3a631bf4f 100644 --- a/fs/btrfs/tests/extent-map-tests.c +++ b/fs/btrfs/tests/extent-map-tests.c @@ -15,6 +15,7 @@ static void free_extent_map_tree(struct extent_map_tree *em_tree) struct extent_map *em; struct rb_node *node; + write_lock(&em_tree->lock); while (!RB_EMPTY_ROOT(&em_tree->map.rb_root)) { node = rb_first_cached(&em_tree->map); em = rb_entry(node, struct extent_map, rb_node); @@ -32,6 +33,7 @@ static void free_extent_map_tree(struct extent_map_tree *em_tree) #endif free_extent_map(em); } + write_unlock(&em_tree->lock); } /*