| Message ID | 20220224122614.94921-6-david@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: COW fixes part 2: reliable GUP pins of anonymous pages | expand |
On Thu, Feb 24, 2022 at 4:29 AM David Hildenbrand <david@redhat.com> wrote: > > ... and instead convert page_add_anon_rmap() to accept flags. Can you fix the comment above the RMAP_xyz definitions? That one still says /* bitflags for do_page_add_anon_rmap() */ that tnow no longer exists. Also, while this kind of code isn't unusual, I think it's still confusing: > + page_add_anon_rmap(page, vma, addr, 0); because when reading that, at least I go "what does 0 mean? Is it a page offset, or what?" It might be a good idea to simply add a #define RMAP_PAGE 0x00 or something like that, just to have the callers all make it obvious that we're talking about that RMAP_xyz bits - even if some of them may be default. (Then using an enum of a special type is something we do if we want to add extra clarity or sparse testing, I don't think there are enough users for that to make sense) Linus
On 24.02.22 18:29, Linus Torvalds wrote: > On Thu, Feb 24, 2022 at 4:29 AM David Hildenbrand <david@redhat.com> wrote: >> >> ... and instead convert page_add_anon_rmap() to accept flags. > > Can you fix the comment above the RMAP_xyz definitions? That one still says > > /* bitflags for do_page_add_anon_rmap() */ > > that tnow no longer exists. Oh, yes sure. > > Also, while this kind of code isn't unusual, I think it's still confusing: > >> + page_add_anon_rmap(page, vma, addr, 0); > > because when reading that, at least I go "what does 0 mean? Is it a > page offset, or what?" Yes, I agree. > > It might be a good idea to simply add a > > #define RMAP_PAGE 0x00 > > or something like that, just to have the callers all make it obvious > that we're talking about that RMAP_xyz bits - even if some of them may > be default. > > (Then using an enum of a special type is something we do if we want to > add extra clarity or sparse testing, I don't think there are enough > users for that to make sense) > Actually, I thought about doing it similarly to what I did in page_alloc.c with fpi_t: typedef int __bitwise fpi_t; #define FPI_NONE ((__force fpi_t)0) I can do something similar here.
On Thu, Feb 24, 2022 at 9:41 AM David Hildenbrand <david@redhat.com> wrote: > > Actually, I thought about doing it similarly to what I did in > page_alloc.c with fpi_t: > > typedef int __bitwise fpi_t; > > #define FPI_NONE ((__force fpi_t)0) > > I can do something similar here. Yeah, that looks good. And then the relevant function declarations and definitions also have that explicit type there instead of 'int', which adds a bit more documentation for people grepping for use. Thanks, Linus
On 24.02.22 18:48, Linus Torvalds wrote: > On Thu, Feb 24, 2022 at 9:41 AM David Hildenbrand <david@redhat.com> wrote: >> >> Actually, I thought about doing it similarly to what I did in >> page_alloc.c with fpi_t: >> >> typedef int __bitwise fpi_t; >> >> #define FPI_NONE ((__force fpi_t)0) >> >> I can do something similar here. > > Yeah, that looks good. And then the relevant function declarations and > definitions also have that explicit type there instead of 'int', which > adds a bit more documentation for people grepping for use. > While at it already, I'll also add a patch to drop the "bool compound" parameter from page_add_new_anon_rmap() (description only) Author: David Hildenbrand <david@redhat.com> Date: Fri Feb 25 09:38:11 2022 +0100 mm/rmap: drop "compound" parameter from page_add_new_anon_rmap() New anonymous pages are always mapped natively: only THP/khugepagd code maps a new compound anonymous page and passes "true". Otherwise, we're just dealing with simple, non-compound pages. Let's give the interface clearer semantics and document these. Signed-off-by: David Hildenbrand <david@redhat.com>
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 92c3585b8c6a..f230e86b4587 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -167,9 +167,7 @@ struct anon_vma *page_get_anon_vma(struct page *page); */ void page_move_anon_rmap(struct page *, struct vm_area_struct *); void page_add_anon_rmap(struct page *, struct vm_area_struct *, - unsigned long, bool); -void do_page_add_anon_rmap(struct page *, struct vm_area_struct *, - unsigned long, int); + unsigned long, int); void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long, bool); void page_add_file_rmap(struct page *, bool); diff --git a/mm/huge_memory.c b/mm/huge_memory.c index c126d728b8de..2ca137e01e84 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3115,7 +3115,7 @@ void remove_migration_pmd(struct page_vma_mapped_walk *pvmw, struct page *new) flush_cache_range(vma, mmun_start, mmun_start + HPAGE_PMD_SIZE); if (PageAnon(new)) - page_add_anon_rmap(new, vma, mmun_start, true); + page_add_anon_rmap(new, vma, mmun_start, RMAP_COMPOUND); else page_add_file_rmap(new, true); set_pmd_at(mm, mmun_start, pvmw->pmd, pmde); diff --git a/mm/ksm.c b/mm/ksm.c index c20bd4d9a0d9..e897577c54c5 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -1153,7 +1153,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, */ if (!is_zero_pfn(page_to_pfn(kpage))) { get_page(kpage); - page_add_anon_rmap(kpage, vma, addr, false); + page_add_anon_rmap(kpage, vma, addr, 0); newpte = mk_pte(kpage, vma->vm_page_prot); } else { newpte = pte_mkspecial(pfn_pte(page_to_pfn(kpage), diff --git a/mm/memory.c b/mm/memory.c index b9602d41d907..c2f1c2428303 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3709,7 +3709,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) page_add_new_anon_rmap(page, vma, vmf->address, false); lru_cache_add_inactive_or_unevictable(page, vma); } else { - do_page_add_anon_rmap(page, vma, vmf->address, exclusive); + page_add_anon_rmap(page, vma, vmf->address, exclusive); } set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); diff --git a/mm/migrate.c b/mm/migrate.c index 524c2648ab36..d4d72a15224c 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -246,7 +246,7 @@ static bool remove_migration_pte(struct page *page, struct vm_area_struct *vma, #endif { if (PageAnon(new)) - page_add_anon_rmap(new, vma, pvmw.address, false); + page_add_anon_rmap(new, vma, pvmw.address, 0); else page_add_file_rmap(new, false); set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); diff --git a/mm/rmap.c b/mm/rmap.c index f825aeef61ca..902ebf99d147 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1129,26 +1129,15 @@ static void __page_check_anon_rmap(struct page *page, * @page: the page to add the mapping to * @vma: the vm area in which the mapping is added * @address: the user virtual address mapped - * @compound: charge the page as compound or small page + * @flags: the rmap flags * * The caller needs to hold the pte lock, and the page must be locked in * the anon_vma case: to serialize mapping,index checking after setting, * and to ensure that PageAnon is not being upgraded racily to PageKsm * (but PageKsm is never downgraded to PageAnon). */ -void page_add_anon_rmap(struct page *page, - struct vm_area_struct *vma, unsigned long address, bool compound) -{ - do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 0); -} - -/* - * Special version of the above for do_swap_page, which often runs - * into pages that are exclusively owned by the current process. - * Everybody else should continue to use page_add_anon_rmap above. - */ -void do_page_add_anon_rmap(struct page *page, - struct vm_area_struct *vma, unsigned long address, int flags) +void page_add_anon_rmap(struct page *page, struct vm_area_struct *vma, + unsigned long address, int flags) { bool compound = flags & RMAP_COMPOUND; bool first; diff --git a/mm/swapfile.c b/mm/swapfile.c index a5183315dc58..eacda7ca7ac9 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1800,7 +1800,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd, inc_mm_counter(vma->vm_mm, MM_ANONPAGES); get_page(page); if (page == swapcache) { - page_add_anon_rmap(page, vma, addr, false); + page_add_anon_rmap(page, vma, addr, 0); } else { /* ksm created a completely new copy */ page_add_new_anon_rmap(page, vma, addr, false); lru_cache_add_inactive_or_unevictable(page, vma);
... and instead convert page_add_anon_rmap() to accept flags. Passing flags instead of bools is usually nicer either way, and we want to more often also pass RMAP_EXCLUSIVE in follow up patches when detecting that an anonymous page is exclusive: for example, when restoring an anonymous page from a writable migration entry. This is a preparation for marking an anonymous page inside page_add_anon_rmap() as exclusive when RMAP_EXCLUSIVE is passed. Signed-off-by: David Hildenbrand <david@redhat.com> --- include/linux/rmap.h | 4 +--- mm/huge_memory.c | 2 +- mm/ksm.c | 2 +- mm/memory.c | 2 +- mm/migrate.c | 2 +- mm/rmap.c | 17 +++-------------- mm/swapfile.c | 2 +- 7 files changed, 9 insertions(+), 22 deletions(-)