io_uring: only test SQPOLL cpu after we've verified it (917257da) · Commits · 戴 / test

We currently call cpu_possible() even if we don't use the CPU. Move the test under the SQ_AFF branch, which is the only place where we'll use the value. Do the cpu_possible() test AFTER we've limited it to a max of NR_CPUS. This avoids triggering the following warning: WARNING: CPU: 1 PID: 7600 at include/linux/cpumask.h:121 cpu_max_bits_warn if CONFIG_DEBUG_PER_CPU_MAPS is enabled. While in there, also move the SQ thread idle period assignment inside SETUP_SQPOLL, as we don't use it otherwise either. Reported-by:

<syzbot+cd714a07c6de2bc34293@syzkaller.appspotmail.com> Fixes: ("io_uring: add submission polling") Signed-off-by:

Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -2241,10 +2241,6 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
		mmgrab(current->mm);
		ctx->sqo_mm = current->mm;

		ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
		if (!ctx->sq_thread_idle)
		ctx->sq_thread_idle = HZ;

		ret = -EINVAL;
		if (!cpu_possible(p->sq_thread_cpu))
		goto err;
		@@ -2254,10 +2250,18 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
		if (!capable(CAP_SYS_ADMIN))
		goto err;

		ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
		if (!ctx->sq_thread_idle)
		ctx->sq_thread_idle = HZ;

		if (p->flags & IORING_SETUP_SQ_AFF) {
		int cpu;

		cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS);
		ret = -EINVAL;
		if (!cpu_possible(p->sq_thread_cpu))
		goto err;

		ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
		ctx, cpu,
		"io_uring-sq");

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