From: Ammar Faizi <ammarfaizi2@gnuweeb.org>
To: Oscar Salvador <osalvador@suse.de>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux MM Mailing List <linux-mm@kvack.org>,
Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
Eric Dumazet <edumazet@google.com>,
Waiman Long <longman@redhat.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH 3/3] mm,page_owner: Filter out stacks by a threshold counter
Date: Thu, 1 Sep 2022 15:31:51 +0700 [thread overview]
Message-ID: <3c69f09e-1e34-73f9-b38b-733971ef38cb@gnuweeb.org> (raw)
In-Reply-To: <20220901044249.4624-4-osalvador@suse.de>
On 9/1/22 11:42 AM, Oscar Salvador wrote:> +static ssize_t read_page_owner_threshold(struct file *file, char __user *buf,
> + size_t count, loff_t *pos)
> +{
> + char *kbuf;
> + int ret = 0;
> +
> + count = min_t(size_t, count, PAGE_SIZE);
> +
> + if (*pos >= count)
> + return 0;
> +
> + kbuf = kmalloc(count, GFP_KERNEL);
> + if (!kbuf)
> + return ENOMEM;
Missing a negative sign, return -ENOMEM.
> + ret = scnprintf(kbuf, count, "%lu\n", threshold_count);
> + if (copy_to_user(buf, kbuf, ret))
> + ret = -EFAULT;
> +
> + *pos += count;
> + kfree(kbuf);
> +
> + return ret;
> +}
> +
> +static ssize_t write_page_owner_threshold(struct file *file, const char __user *buf,
> + size_t count, loff_t *pos)
> +{
> + char *kbuf;
> + int ret = 0;
> +
> + count = min_t(size_t, count, PAGE_SIZE);
> + kbuf = kmalloc(count, GFP_KERNEL);
This looks overestimating to me. For unsigned long, on a 64-bit system
has max val 18446744073709551615 (20 chars).
You can use stack a allocated local variable with length 21. No need
to use kmalloc(). The same way with the read() op.
> + if (!kbuf)
> + return -ENOMEM;
> +
> + if (copy_from_user(kbuf, buf, count)) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + kbuf[count - 1] = '\0';
> +
> + ret = kstrtoul(kbuf, 10, &threshold_count);
> +
> +out:
> + kfree(kbuf);
> + return ret ? ret : count;
> +}
> +
> +static const struct file_operations proc_page_owner_threshold = {
> + .read = read_page_owner_threshold,
> + .write = write_page_owner_threshold,
> +};
--
Ammar Faizi
next prev parent reply other threads:[~2022-09-01 8:32 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 4:42 [PATCH 0/3] page_owner: print stacks and their counter Oscar Salvador
2022-09-01 4:42 ` [PATCH 1/3] lib/stackdepot: Add a refcount field in stack_record Oscar Salvador
2022-09-01 8:24 ` Marco Elver
2022-09-01 8:38 ` Michal Hocko
2022-09-01 9:18 ` Marco Elver
2022-09-01 10:01 ` Michal Hocko
2022-09-01 10:20 ` Marco Elver
2022-09-05 20:53 ` Andrey Konovalov
2022-09-02 3:27 ` Oscar Salvador
2022-09-01 4:42 ` [PATCH 2/3] mm, page_owner: Add page_owner_stacks file to print out only stacks and their counter Oscar Salvador
2022-09-01 8:16 ` Ammar Faizi
2022-09-02 3:33 ` Oscar Salvador
2022-09-01 19:29 ` kernel test robot
2022-09-02 0:56 ` kernel test robot
2022-09-01 4:42 ` [PATCH 3/3] mm,page_owner: Filter out stacks by a threshold counter Oscar Salvador
2022-09-01 8:31 ` Ammar Faizi [this message]
2022-09-02 3:36 ` Oscar Salvador
2022-09-01 8:40 ` Michal Hocko
2022-09-02 3:37 ` Oscar Salvador
2022-09-01 8:32 ` [PATCH 0/3] page_owner: print stacks and their counter Michal Hocko
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