linux-kernel - Re: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs

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Date:   Mon, 20 Feb 2023 15:17:02 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Muhammad Usama Anjum <usama.anjum@...labora.com>
Cc:     Peter Xu <peterx@...hat.com>, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <emmir@...gle.com>,
        Andrei Vagin <avagin@...il.com>,
        Danylo Mocherniuk <mdanylo@...gle.com>,
        Paul Gofman <pgofman@...eweavers.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Yun Zhou <yun.zhou@...driver.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alex Sierra <alex.sierra@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Nadav Amit <namit@...are.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        Greg KH <gregkh@...uxfoundation.org>, kernel@...labora.com
Subject: Re: [PATCH v10 3/6] fs/proc/task_mmu: Implement IOCTL to get and/or
 the clear info about PTEs

On Mon, Feb 20, 2023 at 04:38:10PM +0500, Muhammad Usama Anjum wrote:
> On 2/20/23 3:38 PM, Muhammad Usama Anjum wrote:
> >>> +#define PAGEMAP_BITS_ALL		(PAGE_IS_WRITTEN | PAGE_IS_FILE |	\
> >>> +					 PAGE_IS_PRESENT | PAGE_IS_SWAPPED)
> >>> +#define PAGEMAP_NON_WRITTEN_BITS	(PAGE_IS_FILE |	PAGE_IS_PRESENT | PAGE_IS_SWAPPED)
> >>> +#define IS_WP_ENGAGE_OP(a)		(a->flags & PAGEMAP_WP_ENGAGE)
> >>> +#define IS_GET_OP(a)			(a->vec)
> >>> +#define HAS_NO_SPACE(p)			(p->max_pages && (p->found_pages == p->max_pages))
> >>> +
> >>> +#define PAGEMAP_SCAN_BITMAP(wt, file, present, swap)	\
> >>> +	(wt | file << 1 | present << 2 | swap << 3)
> >>> +#define IS_WT_REQUIRED(a)				\
> >>> +	((a->required_mask & PAGE_IS_WRITTEN) ||	\
> >>> +	 (a->anyof_mask & PAGE_IS_WRITTEN))
> >> All these macros are specific to pagemap_scan_ioctl() and should be
> >> namespaced accordingly, e.g. PM_SCAN_BITS_ALL, PM_SCAN_BITMAP etc.
> >>
> >> Also, IS_<opname>_OP() will be more readable as PM_SCAN_OP_IS_<opname> and
> >> I'd suggest to open code IS_WP_ENGAGE_OP() and IS_GET_OP() and make
> >> HAS_NO_SPACE() and IS_WT_REQUIRED() static inlines rather than macros.
> > Will do in next version.
> > 
> 
> IS_WP_ENGAGE_OP() and IS_GET_OP() which can be renamed to
> PM_SCAN_OP_IS_WP() and PM_SCAN_OP_IS_GET() seem better to me instead of
> open code as they seem more readable to me. I can open code if you insist.

I'd suggest to see how the rework of pagemap_scan_pmd_entry() paves out. An
open-coded '&' is surely clearer than a macro/function, but if it's buried
in a long sequence of conditions, it may be not such clear win.
 
> -- 
> BR,
> Muhammad Usama Anjum

-- 
Sincerely yours,
Mike.