* FAILED: patch "[PATCH] io_uring: wait potential ->release() on resurrect" failed to apply to 5.11-stable tree
@ 2021-03-01 12:12 gregkh
0 siblings, 0 replies; only message in thread
From: gregkh @ 2021-03-01 12:12 UTC (permalink / raw)
To: asml.silence, axboe, stable; +Cc: stable
The patch below does not apply to the 5.11-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 88f171ab7798a1ed0b9e39867ee16f307466e870 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Sat, 20 Feb 2021 18:03:50 +0000
Subject: [PATCH] io_uring: wait potential ->release() on resurrect
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@vger.kernel.org> # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index c98b673f0bb1..5cc02226bb38 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)
@@ -7329,13 +7344,11 @@ 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);
@@ -10070,10 +10083,8 @@ 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) {
@@ -10165,7 +10176,6 @@ 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;
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2021-03-01 12:12 FAILED: patch "[PATCH] io_uring: wait potential ->release() on resurrect" failed to apply to 5.11-stable tree gregkh
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