From: Filipe Manana Date: Mon, 12 Oct 2020 10:55:25 +0000 (+0100) Subject: btrfs: assert we are holding the reada_lock when releasing a readahead zone X-Git-Tag: accepted/tizen/unified/20230118.172025~7911^2~216 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a57ad681f12e1ec80365fc4693e12e979159b9d0;p=platform%2Fkernel%2Flinux-rpi.git btrfs: assert we are holding the reada_lock when releasing a readahead zone When we drop the last reference of a zone, we end up releasing it through the callback reada_zone_release(), which deletes the zone from a device's reada_zones radix tree. This tree is protected by the global readahead lock at fs_info->reada_lock. Currently all places that are sure that they are dropping the last reference on a zone, are calling kref_put() in a critical section delimited by this lock, while all other places that are sure they are not dropping the last reference, do not bother calling kref_put() while holding that lock. When working on the previous fix for hangs and use-after-frees in the readahead code, my initial attempts were different and I actually ended up having reada_zone_release() called when not holding the lock, which resulted in weird and unexpected problems. So just add an assertion there to detect such problem more quickly and make the dependency more obvious. Reviewed-by: Johannes Thumshirn Reviewed-by: Josef Bacik Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c index d9a166e..6e33cb7 100644 --- a/fs/btrfs/reada.c +++ b/fs/btrfs/reada.c @@ -531,6 +531,8 @@ static void reada_zone_release(struct kref *kref) { struct reada_zone *zone = container_of(kref, struct reada_zone, refcnt); + lockdep_assert_held(&zone->device->fs_info->reada_lock); + radix_tree_delete(&zone->device->reada_zones, zone->end >> PAGE_SHIFT);