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io_uring-5.6-2020-03-13

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Merge tag 'io_uring-5.6-2020-03-13' of git://git.kernel.dk/linux-block

Pull io_uring fix from Jens Axboe:
 "Just a single fix here, improving the RCU callback ordering from last
  week. After a bit more perusing by Paul, he poked a hole in the
  original"

* tag 'io_uring-5.6-2020-03-13' of git://git.kernel.dk/linux-block:
  io_uring: ensure RCU callback ordering with rcu_barrier()
This commit is contained in:
Linus Torvalds 2020-03-13 13:00:08 -07:00
commit 5007928eae
1 changed files with 14 additions and 17 deletions
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31
fs/io_uring.c
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@ -191,7 +191,6 @@ struct fixed_file_data {
struct llist_head put_llist;
struct work_struct ref_work;
struct completion done;
struct rcu_head rcu;
};
struct io_ring_ctx {
@ -5331,26 +5330,23 @@ static void io_file_ref_kill(struct percpu_ref *ref)
complete(&data->done);
}
static void __io_file_ref_exit_and_free(struct rcu_head *rcu)
static void io_file_ref_exit_and_free(struct work_struct *work)
{
struct fixed_file_data *data = container_of(rcu, struct fixed_file_data,
rcu);
struct fixed_file_data *data;
data = container_of(work, struct fixed_file_data, ref_work);
/*
* Ensure any percpu-ref atomic switch callback has run, it could have
* been in progress when the files were being unregistered. Once
* that's done, we can safely exit and free the ref and containing
* data structure.
*/
rcu_barrier();
percpu_ref_exit(&data->refs);
kfree(data);
}
static void io_file_ref_exit_and_free(struct rcu_head *rcu)
{
/*
* We need to order our exit+free call against the potentially
* existing call_rcu() for switching to atomic. One way to do that
* is to have this rcu callback queue the final put and free, as we
* could otherwise have a pre-existing atomic switch complete _after_
* the free callback we queued.
*/
call_rcu(rcu, __io_file_ref_exit_and_free);
}
static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
struct fixed_file_data *data = ctx->file_data;
@ -5369,7 +5365,8 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
for (i = 0; i < nr_tables; i++)
kfree(data->table[i].files);
kfree(data->table);
call_rcu(&data->rcu, io_file_ref_exit_and_free);
INIT_WORK(&data->ref_work, io_file_ref_exit_and_free);
queue_work(system_wq, &data->ref_work);
ctx->file_data = NULL;
ctx->nr_user_files = 0;
return 0;