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Subject: Re: [PATCH v2 4/5] blk-iocost: fix sleeping in atomic context
 warnning
To:     Tejun Heo <tj@kernel.org>, 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>
References: <20221104023938.2346986-1-yukuai1@huaweicloud.com>
 <20221104023938.2346986-5-yukuai1@huaweicloud.com>
 <Y3K8MSFWw8eTnxtm@slm.duckdns.org>
From:   Yu Kuai <yukuai1@huaweicloud.com>
Message-ID: <3da991c6-21e4-8ed8-ba75-ccb92059f0ae@huaweicloud.com>
Date:   Thu, 17 Nov 2022 19:28:50 +0800
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Hi, Tejun!

?? 2022/11/15 6:07, Tejun Heo д??:

> 
> 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().

Thanks,
Kuai
> 
> Thanks.
>