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Wed, 26 Aug 2020 07:21:17 -0700 (PDT) Date: Wed, 26 Aug 2020 10:20:02 -0400 From: Johannes Weiner To: "Matthew Wilcox (Oracle)" Cc: linux-mm@kvack.org, Andrew Morton , Hugh Dickins , William Kucharski , Jani Nikula , Alexey Dobriyan , Chris Wilson , Matthew Auld , Huang Ying , intel-gfx@lists.freedesktop.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/8] mm: Use find_get_swap_page in memcontrol Message-ID: <20200826142002.GA988805@cmpxchg.org> References: <20200819184850.24779-1-willy@infradead.org> <20200819184850.24779-3-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200819184850.24779-3-willy@infradead.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 19, 2020 at 07:48:44PM +0100, Matthew Wilcox (Oracle) wrote: > The current code does not protect against swapoff of the underlying > swap device, so this is a bug fix as well as a worthwhile reduction in > code complexity. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/memcontrol.c | 25 ++----------------------- > 1 file changed, 2 insertions(+), 23 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index b807952b4d43..4075f214a841 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5539,35 +5539,14 @@ static struct page *mc_handle_swap_pte(struct vm_area_struct *vma, > static struct page *mc_handle_file_pte(struct vm_area_struct *vma, > unsigned long addr, pte_t ptent, swp_entry_t *entry) > { > - struct page *page = NULL; > - struct address_space *mapping; > - pgoff_t pgoff; > - > if (!vma->vm_file) /* anonymous vma */ > return NULL; > if (!(mc.flags & MOVE_FILE)) > return NULL; > > - mapping = vma->vm_file->f_mapping; > - pgoff = linear_page_index(vma, addr); > - > /* page is moved even if it's not RSS of this task(page-faulted). */ > -#ifdef CONFIG_SWAP > - /* shmem/tmpfs may report page out on swap: account for that too. */ > - if (shmem_mapping(mapping)) { > - page = find_get_entry(mapping, pgoff); > - if (xa_is_value(page)) { > - swp_entry_t swp = radix_to_swp_entry(page); > - *entry = swp; > - page = find_get_page(swap_address_space(swp), > - swp_offset(swp)); > - } > - } else > - page = find_get_page(mapping, pgoff); > -#else > - page = find_get_page(mapping, pgoff); > -#endif > - return page; > + return find_get_swap_page(vma->vm_file->f_mapping, > + linear_page_index(vma, addr)); The refactor makes sense to me, but the name is confusing. We're not looking for a swap page, we're primarily looking for a file page in the page cache mapping that's handed in. Only in the special case where it's a shmem mapping and there is a swap entry do we consult the auxiliary swap cache. How about find_get_page_or_swapcache()? find_get_page_shmemswap()? Maybe you have a better idea. It's a fairly specialized operation that isn't widely used, so a longer name isn't a bad thing IMO.