On Mon, 2025-03-17 at 11:28 -0700, Bart Van Assche wrote: > On 3/17/25 11:13 AM, Thomas Hellström wrote: > > On Mon, 2025-03-17 at 10:37 -0700, Bart Van Assche wrote: > > > On 3/17/25 10:11 AM, Thomas Hellström wrote: > > > > diff --git a/block/blk-core.c b/block/blk-core.c > > > > index d6c4fa3943b5..4aa439309406 100644 > > > > --- a/block/blk-core.c > > > > +++ b/block/blk-core.c > > > > @@ -455,6 +455,12 @@ struct request_queue > > > > *blk_alloc_queue(struct > > > > queue_limits *lim, int node_id) > > > > lockdep_init_map(&q->q_lockdep_map, "&q- > > > > > q_usage_counter(queue)", > > > > &q->q_lock_cls_key, 0); > > > > > > > > + /* Prime io_lockdep_map as reclaim tainted */ > > > > + fs_reclaim_acquire(GFP_KERNEL); > > > > + rwsem_acquire_read(&q->io_lockdep_map, 0, 0, > > > > _RET_IP_); > > > > + rwsem_release(&q->io_lockdep_map, _RET_IP_); > > > > + fs_reclaim_release(GFP_KERNEL); > > > > + > > > > q->nr_requests = BLKDEV_DEFAULT_RQ; > > > > > > > > return q; > > > > > > Hmm ... my understanding is that it is fine if FS code calls > > > block > > > layer > > > code but also that block layer code never should call FS code. > > > > That added code only mimics the locking sequence that happens > > during > > reclaim with the existing code to register the locking order > > expected > > by the reclaim code. If anything violates that, lockdep splat [2] > > will > > appear. > > > > So I'm not quite following your comment? > Shouldn't the above code be added in the VFS code rather than in the > block layer? It registers a known locking order WRT reclaim(GFP_KERNEL) for the q- >io_lockdep_map, which is itself initialized in this function. I believe any known locking orders should be registered at the place the lockdep map is initialized. Thanks, Thomas > > Thanks, > > Bart.
