There is a short window where percpu_refs are already turned zero, but
we try to do resurrect(). Play nicer and wait for ->release() to happen
in this case and proceed as everything is ok. One downside for ctx refs
is that we can ignore signal_pending() on a rare occasion, but someone
else should check for it later if needed.
Cc: <stable@xxxxxxxxxxxxxxx> # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b00ab7138410..ce197af2d3c6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1104,6 +1104,21 @@ static inline void io_set_resource_node(struct io_kiocb *req)
}
}
+static bool io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
+{
+ if (!percpu_ref_tryget(ref)) {
+ /* already at zero, wait for ->release() */
+ if (!try_wait_for_completion(compl))
+ synchronize_rcu();
+ return false;
+ }
+
+ percpu_ref_resurrect(ref);
+ reinit_completion(compl);
+ percpu_ref_put(ref);
+ return true;
+}
+
static bool io_match_task(struct io_kiocb *head,
struct task_struct *task,
struct files_struct *files)
@@ -7353,13 +7368,11 @@ static int io_rsrc_ref_quiesce(struct fixed_rsrc_data *data,
flush_delayed_work(&ctx->rsrc_put_work);
ret = wait_for_completion_interruptible(&data->done);
- if (!ret)
+ if (!ret || !io_refs_resurrect(&data->refs, &data->done))
break;
- percpu_ref_resurrect(&data->refs);
io_sqe_rsrc_set_node(ctx, data, backup_node);
backup_node = NULL;
- reinit_completion(&data->done);
mutex_unlock(&ctx->uring_lock);
ret = io_run_task_work_sig();
mutex_lock(&ctx->uring_lock);
@@ -10094,10 +10107,8 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
mutex_lock(&ctx->uring_lock);
- if (ret) {
- percpu_ref_resurrect(&ctx->refs);
- goto out_quiesce;
- }
+ if (ret && io_refs_resurrect(&ctx->refs, &ctx->ref_comp))
+ return ret;
}
if (ctx->restricted) {
@@ -10189,7 +10200,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
if (io_register_op_must_quiesce(opcode)) {
/* bring the ctx back to life */
percpu_ref_reinit(&ctx->refs);
-out_quiesce:
reinit_completion(&ctx->ref_comp);
}
return ret;
--
2.24.0
