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Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, kernel-team@meta.com Subject: Re: [PATCH v2 2/6] mm: extract mm_prepare_for_swap_entries() helper Message-ID: References: <20260706114320.1643046-1-usama.arif@linux.dev> <20260706114320.1643046-3-usama.arif@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260706114320.1643046-3-usama.arif@linux.dev> On Mon, Jul 06, 2026 at 04:42:04AM -0700, Usama Arif wrote: > When a swap entry is installed in a page table, the mm must be added > to init_mm.mmlist so that swapoff can find and unuse its swap entries. > This double-checked locking pattern is currently open-coded in > try_to_unmap_one() and copy_nonpresent_pte(). > > Move it into mm_prepare_for_swap_entries() in mm/internal.h and convert > both callers so it can be reused by upcoming PMD-level swap entry code > paths that also need to register the mm with swapoff. > > copy_nonpresent_pte() previously inserted into &src_mm->mmlist rather > than &init_mm.mmlist, but the insertion point is irrelevant, mmlist > is a circular list and swapoff walks it entirely from init_mm.mmlist, > so only membership matters, not position. > > Reviewed-by: Dev Jain > Reviewed-by: Zi Yan > Acked-by: David Hildenbrand (Arm) > Signed-off-by: Usama Arif > --- > mm/internal.h | 10 ++++++++++ > mm/memory.c | 9 +-------- > mm/rmap.c | 7 +------ > 3 files changed, 12 insertions(+), 14 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 430aa72a4575..0360648e5726 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -1955,4 +1955,14 @@ static inline int get_sysctl_max_map_count(void) > bool may_expand_vm(struct mm_struct *mm, const vma_flags_t *vma_flags, > unsigned long npages); > > +static inline void mm_prepare_for_swap_entries(struct mm_struct *mm) > +{ > + if (list_empty(&mm->mmlist)) { > + spin_lock(&mmlist_lock); > + if (list_empty(&mm->mmlist)) > + list_add(&mm->mmlist, &init_mm.mmlist); The patch is fine, but the name of the field is awful. Seeing mmlist I assumed it listed all mm_structs. It has to have "swap" somewhere in the field name. -- Kiryl Shutsemau / Kirill A. Shutemov