From: Oscar Salvador <osalvador@suse.de>
To: David Hildenbrand <david@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH v1 2/6] fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT
Date: Mon, 10 Jun 2024 06:38:33 +0200 [thread overview]
Message-ID: <ZmaDSQZlAl7Jb-wi@localhost.localdomain> (raw)
In-Reply-To: <20240607122357.115423-3-david@redhat.com>
On Fri, Jun 07, 2024 at 02:23:53PM +0200, David Hildenbrand wrote:
> Relying on the mapcount for non-present PTEs that reference pages
> doesn't make any sense: they are not accounted in the mapcount, so
> page_mapcount() == 1 won't return the result we actually want to know.
>
> While we don't check the mapcount for migration entries already, we
> could end up checking it for swap, hwpoison, device exclusive, ...
> entries, which we really shouldn't.
>
> There is one exception: device private entries, which we consider
> fake-present (e.g., incremented the mapcount). But we won't care about
> that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them
> although they are fake-present already sounds suspiciously wrong.
>
> Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT.
Alternatively we could use is_pfn_swap_entry?
But the PM_PRESENT approach seems more correct.
> Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
--
Oscar Salvador
SUSE Labs
next prev parent reply other threads:[~2024-06-10 4:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-07 12:23 [PATCH v1 0/6] fs/proc: move page_mapcount() to fs/proc/internal.h David Hildenbrand
2024-06-07 12:23 ` [PATCH v1 1/6] fs/proc/task_mmu: indicate PM_FILE for PMD-mapped file THP David Hildenbrand
2024-06-07 13:21 ` Kirill A . Shutemov
2024-06-07 13:36 ` Lance Yang
2024-06-10 4:32 ` Oscar Salvador
2024-06-07 12:23 ` [PATCH v1 2/6] fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT David Hildenbrand
2024-06-10 4:38 ` Oscar Salvador [this message]
2024-06-11 7:13 ` Oscar Salvador
2024-06-11 10:51 ` David Hildenbrand
2024-06-11 10:45 ` David Hildenbrand
2024-06-10 4:49 ` Oscar Salvador
2024-06-11 10:50 ` David Hildenbrand
2024-06-11 11:15 ` Oscar Salvador
2024-06-07 12:23 ` [PATCH v1 3/6] fs/proc/task_mmu: properly detect PM_MMAP_EXCLUSIVE per page of PMD-mapped THPs David Hildenbrand
2024-06-10 4:51 ` Oscar Salvador
2024-06-07 12:23 ` [PATCH v1 4/6] fs/proc/task_mmu: account non-present entries as "maybe shared, but no idea how often" David Hildenbrand
2024-06-07 12:23 ` [PATCH v1 5/6] fs/proc: move page_mapcount() to fs/proc/internal.h David Hildenbrand
2024-06-07 12:23 ` [PATCH v1 6/6] Documentation/admin-guide/mm/pagemap.rst: drop "Using pagemap to do something useful" David Hildenbrand
2024-06-07 13:18 ` [PATCH v1 0/6] fs/proc: move page_mapcount() to fs/proc/internal.h Oscar Salvador
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