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Sender: Tejun Heo <htejun@gmail.com>
Date:   Tue, 22 Nov 2022 11:10:28 -1000
From:   Tejun Heo <tj@kernel.org>
To:     Yu Kuai <yukuai1@huaweicloud.com>
Cc:     hch@lst.de, josef@toxicpanda.com, axboe@kernel.dk,
        cgroups@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, yi.zhang@huawei.com,
        "yukuai (C)" <yukuai3@huawei.com>
Subject: Re: [PATCH v2 4/5] blk-iocost: fix sleeping in atomic context
 warnning
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On Thu, Nov 17, 2022 at 07:28:50PM +0800, Yu Kuai wrote:
> Hi, Tejun!
> 
> 在 2022/11/15 6:07, Tejun Heo 写道:
> 
> > 
> > Any chance I can persuade you into updating match_NUMBER() helpers to not
> > use match_strdup()? They can easily disable irq/preemption and use percpu
> > buffers and we won't need most of this patchset.
> 
> Does the following patch match your proposal?
> 
> diff --git a/lib/parser.c b/lib/parser.c
> index bcb23484100e..ded652471919 100644
> --- a/lib/parser.c
> +++ b/lib/parser.c
> @@ -11,6 +11,24 @@
>  #include <linux/slab.h>
>  #include <linux/string.h>
> 
> +#define U64_MAX_SIZE 20
> +
> +static DEFINE_PER_CPU(char, buffer[U64_MAX_SIZE]);
> +
> +static char *get_buffer(void)
> +{
> +       preempt_disable();
> +       local_irq_disable();
> +
> +       return this_cpu_ptr(buffer);
> +}
> +
> +static void put_buffer(void)
> +{
> +       local_irq_enable();
> +       preempt_enable();
> +}
> +
> 
> Then match_strdup() and kfree() in match_NUMBER() can be replaced with
> get_buffer() and put_buffer().

Sorry about the late reply. Yeah, something like this.

Thanks.

-- 
tejun