在 2021/2/20 上午4:45, Pavel Begunkov 写道:
There are different types of races in io_rsrc_ref_quiesce() between
->release() of percpu_refs and reinit_completion(), fix them by always
resurrecting between iterations. BTW, clean the function up, because
DRY.
Fixes: 0ce4a72632317 ("io_uring: don't hold uring_lock when calling io_run_task_work*")
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 46 +++++++++++++---------------------------------
1 file changed, 13 insertions(+), 33 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 50d4dba08f82..38ed52065a29 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7316,19 +7316,6 @@ static void io_sqe_rsrc_set_node(struct io_ring_ctx *ctx,
percpu_ref_get(&rsrc_data->refs);
}
-static int io_sqe_rsrc_add_node(struct io_ring_ctx *ctx, struct fixed_rsrc_data *data)
-{
- struct fixed_rsrc_ref_node *backup_node;
-
- backup_node = alloc_fixed_rsrc_ref_node(ctx);
- if (!backup_node)
- return -ENOMEM;
- init_fixed_file_ref_node(ctx, backup_node);
- io_sqe_rsrc_set_node(ctx, data, backup_node);
-
- return 0;
-}
-
static void io_sqe_rsrc_kill_node(struct io_ring_ctx *ctx, struct fixed_rsrc_data *data)
{
struct fixed_rsrc_ref_node *ref_node = NULL;
@@ -7347,36 +7334,29 @@ static int io_rsrc_ref_quiesce(struct fixed_rsrc_data *data,
{
int ret;
- io_sqe_rsrc_kill_node(ctx, data);
- percpu_ref_kill(&data->refs);
-
- /* wait for all refs nodes to complete */
- flush_delayed_work(&ctx->rsrc_put_work);
do {
+ io_sqe_rsrc_kill_node(ctx, data);
+ percpu_ref_kill(&data->refs);
+ flush_delayed_work(&ctx->rsrc_put_work);
+
ret = wait_for_completion_interruptible(&data->done);
if (!ret)
break;
- ret = io_sqe_rsrc_add_node(ctx, data);
- if (ret < 0)
- break;
- /*
- * There is small possibility that data->done is already completed
- * So reinit it here
- */
+ percpu_ref_resurrect(&data->refs);
I've thought about this, if we resurrect data->refs, then we can't
avoid parallel files unregister by percpu_refs_is_dying.
+ io_sqe_rsrc_set_node(ctx, data, backup_node);
reinit_completion(&data->done);
mutex_unlock(&ctx->uring_lock);
ret = io_run_task_work_sig();
mutex_lock(&ctx->uring_lock);
- io_sqe_rsrc_kill_node(ctx, data);
- } while (ret >= 0);
- if (ret < 0) {
- percpu_ref_resurrect(&data->refs);
- reinit_completion(&data->done);
- io_sqe_rsrc_set_node(ctx, data, backup_node);
- return ret;
- }
+ if (ret < 0)
+ return ret;
+ backup_node = alloc_fixed_rsrc_ref_node(ctx);
+ if (!backup_node)
+ return -ENOMEM;
Should we resurrect data->refs and reinit completion before
signal or error return?
+ init_fixed_file_ref_node(ctx, backup_node);
+ } while (1);
destroy_fixed_rsrc_ref_node(backup_node);
return 0;
