Re: [PATCH 5.15.y] mm/damon/ops-common: atomically test and clear young on ptes and pmds

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jul 17, 2023 at 07:30:08PM +0000, SeongJae Park wrote:
> From: Ryan Roberts <ryan.roberts@arm.com>
> 
> commit c11d34fa139e4b0fb4249a30f37b178353533fa1 upstream.
> 
> It is racy to non-atomically read a pte, then clear the young bit, then
> write it back as this could discard dirty information.  Further, it is bad
> practice to directly set a pte entry within a table.  Instead clearing
> young must go through the arch-provided helper,
> ptep_test_and_clear_young() to ensure it is modified atomically and to
> give the arch code visibility and allow it to check (and potentially
> modify) the operation.
> 
> Link: https://lkml.kernel.org/r/20230602092949.545577-3-ryan.roberts@arm.com
> Fixes: 3f49584b262c ("mm/damon: implement primitives for the virtual memory address spaces").
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> Reviewed-by: Zi Yan <ziy@nvidia.com>
> Reviewed-by: SeongJae Park <sj@kernel.org>
> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Lorenzo Stoakes <lstoakes@gmail.com>
> Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
> Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
> Cc: Yu Zhao <yuzhao@google.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: SeongJae Park <sj@kernel.org>
> ---
> This is a manual backport of the commit, which cannot cleanly
> cherry-picked on 5.15.y[1], on 5.15.y, specifically 5.15.120.
> 
> [1] https://lore.kernel.org/stable/2023071613-reminder-relapse-b922@gregkh/

Now queued up, thanks.

greg k-h