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Subject: Re: [PATCH v4] mm: cma: support sysfs
From:   Dmitry Osipenko <digetx@gmail.com>
To:     Minchan Kim <minchan@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        joaodias@google.com, willy@infradead.org, david@redhat.com,
        surenb@google.com, Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Nicolas Chauvet <kwizart@gmail.com>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>
References: <20210309062333.3216138-1-minchan@kernel.org>
 <fead70a2-4330-79ff-e79a-d8511eab1256@gmail.com>
Message-ID: <e8ae901d-9521-8de4-ee45-18cb55b8f29c@gmail.com>
Date:   Fri, 19 Mar 2021 16:39:41 +0300
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19.03.2021 15:44, Dmitry Osipenko пишет:
...
>>  #include <linux/debugfs.h>
>> +#include <linux/kobject.h>
>> +
>> +struct cma_stat {
>> +	spinlock_t lock;
>> +	/* the number of CMA page successful allocations */
>> +	unsigned long nr_pages_succeeded;
>> +	/* the number of CMA page allocation failures */
>> +	unsigned long nr_pages_failed;
>> +	struct kobject kobj;
>> +};
>>  
>>  struct cma {
>>  	unsigned long   base_pfn;
>> @@ -16,6 +26,9 @@ struct cma {
>>  	struct debugfs_u32_array dfs_bitmap;
>>  #endif
>>  	char name[CMA_MAX_NAME];
>> +#ifdef CONFIG_CMA_SYSFS
>> +	struct cma_stat	*stat;
>> +#endif

What is the point of allocating stat dynamically?

...
>> +void cma_sysfs_alloc_pages_count(struct cma *cma, size_t count)
>> +{
>> +	spin_lock(&cma->stat->lock);
>> +	cma->stat->nr_pages_succeeded += count;
>> +	spin_unlock(&cma->stat->lock);
>> +}
>> +
>> +void cma_sysfs_fail_pages_count(struct cma *cma, size_t count)
>> +{
>> +	spin_lock(&cma->stat->lock);
>> +	cma->stat->nr_pages_failed += count;
>> +	spin_unlock(&cma->stat->lock);
>> +}

You could use atomic increment and then locking isn't needed.