Message-ID: <af55d3d8-31d8-0deb-d76f-b6d464ad7262@collabora.com>
Date:   Tue, 21 Feb 2023 12:02:17 +0500
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Cc:     Muhammad Usama Anjum <usama.anjum@collabora.com>,
        Peter Xu <peterx@redhat.com>,
        David Hildenbrand <david@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        <emmir@google.com>, Andrei Vagin <avagin@gmail.com>,
        Danylo Mocherniuk <mdanylo@google.com>,
        Paul Gofman <pgofman@codeweavers.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Yang Shi <shy828301@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Liam R . Howlett" <Liam.Howlett@oracle.com>,
        Yun Zhou <yun.zhou@windriver.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Alex Sierra <alex.sierra@amd.com>,
        Matthew Wilcox <willy@infradead.org>,
        Pasha Tatashin <pasha.tatashin@soleen.com>,
        Nadav Amit <namit@vmware.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        Greg KH <gregkh@linuxfoundation.org>, kernel@collabora.com
Subject: Re: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or
 the clear info about PTEs
Content-Language: en-US
To:     Mike Rapoport <rppt@kernel.org>
References: <20230202112915.867409-1-usama.anjum@collabora.com>
 <20230202112915.867409-4-usama.anjum@collabora.com>
 <Y/N1EnEEE9y0qp/n@kernel.org>
From:   Muhammad Usama Anjum <usama.anjum@collabora.com>
In-Reply-To: <Y/N1EnEEE9y0qp/n@kernel.org>
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On 2/20/23 6:26 PM, Mike Rapoport wrote:
> Hi,
> 
> On Thu, Feb 02, 2023 at 04:29:12PM +0500, Muhammad Usama Anjum wrote:
>> This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear
>> the info about page table entries. The following operations are supported
>> in this ioctl:
>> - Get the information if the pages have been written-to (PAGE_IS_WRITTEN),
>>   file mapped (PAGE_IS_FILE), present (PAGE_IS_PRESENT) or swapped
>>   (PAGE_IS_SWAPPED).
>> - Write-protect the pages (PAGEMAP_WP_ENGAGE) to start finding which
>>   pages have been written-to.
>> - Find pages which have been written-to and write protect the pages
>>   (atomic PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE)
>>
>> +/*
>> + * struct pagemap_scan_arg - Pagemap ioctl argument
>> + * @start:		Starting address of the region
>> + * @len:		Length of the region (All the pages in this length are included)
>> + * @vec:		Address of page_region struct array for output
>> + * @vec_len:		Length of the page_region struct array
>> + * @max_pages:		Optional max return pages
>> + * @flags:		Flags for the IOCTL
>> + * @required_mask:	Required mask - All of these bits have to be set in the PTE
>> + * @anyof_mask:		Any mask - Any of these bits are set in the PTE
>> + * @excluded_mask:	Exclude mask - None of these bits are set in the PTE
>> + * @return_mask:	Bits that are to be reported in page_region
>> + */
>> +struct pagemap_scan_arg {
>> +	__u64 start;
>> +	__u64 len;
>> +	__u64 vec;
>> +	__u64 vec_len;
>> +	__u32 max_pages;
>> +	__u32 flags;
>> +	__u64 required_mask;
>> +	__u64 anyof_mask;
>> +	__u64 excluded_mask;
>> +	__u64 return_mask;
>> +};
> 
> After Nadav's comment I've realized I missed the API part :)
> 
> A few quick notes for now:
> * The arg struct is fixed, so it would be impossible to extend the API
> later. Following the clone3() example, I'd add 'size' field to the
> pagemam_scan_arg so that it would be possible to add new fields afterwards.
> * Please make flags __u64, just in case
> * Put size and flags at the beginning of the struct, e.g.
> 
> strucr pagemap_scan_arg {
> 	size_t size;
> 	__u64 flags;
> 	/* all the rest */
> };
Updated. Thank you so much!

> 
>> +
>> +/* Special flags */
>> +#define PAGEMAP_WP_ENGAGE	(1 << 0)
>> +
>>  #endif /* _UAPI_LINUX_FS_H */
>> -- 
>> 2.30.2
>>
> 

-- 
BR,
Muhammad Usama Anjum