| Message ID | 20240321142448.1645400-5-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Various significant MM patches | expand |
On 3/21/24 15:24, Matthew Wilcox (Oracle) wrote: > Return 0 for pages which can't be mapped. This matches how page_mapped() > works. It is more convenient for users to not have to filter out > these pages. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Hm strictly speaking you shouldn't be removing those PageSlab tests until it's changed to a PageType in 7/9? If we're paranoid enough about not breaking bisection between this and that patch. Otherwise Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > fs/proc/page.c | 7 ++----- > include/linux/mm.h | 8 +++++--- > include/linux/page-flags.h | 4 ++-- > 3 files changed, 9 insertions(+), 10 deletions(-) > > diff --git a/fs/proc/page.c b/fs/proc/page.c > index 195b077c0fac..9223856c934b 100644 > --- a/fs/proc/page.c > +++ b/fs/proc/page.c > @@ -67,7 +67,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf, > */ > ppage = pfn_to_online_page(pfn); > > - if (!ppage || PageSlab(ppage) || page_has_type(ppage)) > + if (!ppage) > pcount = 0; > else > pcount = page_mapcount(ppage); > @@ -124,11 +124,8 @@ u64 stable_page_flags(struct page *page) > > /* > * pseudo flags for the well known (anonymous) memory mapped pages > - * > - * Note that page->_mapcount is overloaded in SLAB, so the > - * simple test in page_mapped() is not enough. > */ > - if (!PageSlab(page) && page_mapped(page)) > + if (page_mapped(page)) > u |= 1 << KPF_MMAP; > if (PageAnon(page)) > u |= 1 << KPF_ANON; > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0436b919f1c7..5ff3d687bc6c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1223,14 +1223,16 @@ static inline void page_mapcount_reset(struct page *page) > * a large folio, it includes the number of times this page is mapped > * as part of that folio. > * > - * The result is undefined for pages which cannot be mapped into userspace. > - * For example SLAB or special types of pages. See function page_has_type(). > - * They use this field in struct page differently. > + * Will report 0 for pages which cannot be mapped into userspace, eg > + * slab, page tables and similar. > */ > static inline int page_mapcount(struct page *page) > { > int mapcount = atomic_read(&page->_mapcount) + 1; > > + /* Handle page_has_type() pages */ > + if (mapcount < 0) > + mapcount = 0; > if (unlikely(PageCompound(page))) > mapcount += folio_entire_mapcount(page_folio(page)); > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 8d0e6ce25ca2..5852f967c640 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -971,12 +971,12 @@ static inline bool is_page_hwpoison(struct page *page) > * page_type may be used. Because it is initialised to -1, we invert the > * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and > * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and > - * low bits so that an underflow or overflow of page_mapcount() won't be > + * low bits so that an underflow or overflow of _mapcount won't be > * mistaken for a page type value. > */ > > #define PAGE_TYPE_BASE 0xf0000000 > -/* Reserve 0x0000007f to catch underflows of page_mapcount */ > +/* Reserve 0x0000007f to catch underflows of _mapcount */ > #define PAGE_MAPCOUNT_RESERVE -128 > #define PG_buddy 0x00000080 > #define PG_offline 0x00000100
On Fri, Mar 22, 2024 at 10:43:38AM +0100, Vlastimil Babka wrote: > On 3/21/24 15:24, Matthew Wilcox (Oracle) wrote: > > Return 0 for pages which can't be mapped. This matches how page_mapped() > > works. It is more convenient for users to not have to filter out > > these pages. > > > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > > Hm strictly speaking you shouldn't be removing those PageSlab tests until > it's changed to a PageType in 7/9? If we're paranoid enough about not > breaking bisection between this and that patch. I thought about that. Slub currently doesn't use the field while will become __page_type, so it's left set to -1 by the page allocator. So this is safe. Thanks for checking that though ;-) > Otherwise > > Acked-by: Vlastimil Babka <vbabka@suse.cz> > > > --- > > fs/proc/page.c | 7 ++----- > > include/linux/mm.h | 8 +++++--- > > include/linux/page-flags.h | 4 ++-- > > 3 files changed, 9 insertions(+), 10 deletions(-) > > > > diff --git a/fs/proc/page.c b/fs/proc/page.c > > index 195b077c0fac..9223856c934b 100644 > > --- a/fs/proc/page.c > > +++ b/fs/proc/page.c > > @@ -67,7 +67,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf, > > */ > > ppage = pfn_to_online_page(pfn); > > > > - if (!ppage || PageSlab(ppage) || page_has_type(ppage)) > > + if (!ppage) > > pcount = 0; > > else > > pcount = page_mapcount(ppage); > > @@ -124,11 +124,8 @@ u64 stable_page_flags(struct page *page) > > > > /* > > * pseudo flags for the well known (anonymous) memory mapped pages > > - * > > - * Note that page->_mapcount is overloaded in SLAB, so the > > - * simple test in page_mapped() is not enough. > > */ > > - if (!PageSlab(page) && page_mapped(page)) > > + if (page_mapped(page)) > > u |= 1 << KPF_MMAP; > > if (PageAnon(page)) > > u |= 1 << KPF_ANON; > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 0436b919f1c7..5ff3d687bc6c 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -1223,14 +1223,16 @@ static inline void page_mapcount_reset(struct page *page) > > * a large folio, it includes the number of times this page is mapped > > * as part of that folio. > > * > > - * The result is undefined for pages which cannot be mapped into userspace. > > - * For example SLAB or special types of pages. See function page_has_type(). > > - * They use this field in struct page differently. > > + * Will report 0 for pages which cannot be mapped into userspace, eg > > + * slab, page tables and similar. > > */ > > static inline int page_mapcount(struct page *page) > > { > > int mapcount = atomic_read(&page->_mapcount) + 1; > > > > + /* Handle page_has_type() pages */ > > + if (mapcount < 0) > > + mapcount = 0; > > if (unlikely(PageCompound(page))) > > mapcount += folio_entire_mapcount(page_folio(page)); > > > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > > index 8d0e6ce25ca2..5852f967c640 100644 > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -971,12 +971,12 @@ static inline bool is_page_hwpoison(struct page *page) > > * page_type may be used. Because it is initialised to -1, we invert the > > * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and > > * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and > > - * low bits so that an underflow or overflow of page_mapcount() won't be > > + * low bits so that an underflow or overflow of _mapcount won't be > > * mistaken for a page type value. > > */ > > > > #define PAGE_TYPE_BASE 0xf0000000 > > -/* Reserve 0x0000007f to catch underflows of page_mapcount */ > > +/* Reserve 0x0000007f to catch underflows of _mapcount */ > > #define PAGE_MAPCOUNT_RESERVE -128 > > #define PG_buddy 0x00000080 > > #define PG_offline 0x00000100 >
On 21.03.24 15:24, Matthew Wilcox (Oracle) wrote: > Return 0 for pages which can't be mapped. This matches how page_mapped() > works. It is more convenient for users to not have to filter out > these pages. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/fs/proc/page.c b/fs/proc/page.c index 195b077c0fac..9223856c934b 100644 --- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -67,7 +67,7 @@ static ssize_t kpagecount_read(struct file *file, char __user *buf, */ ppage = pfn_to_online_page(pfn); - if (!ppage || PageSlab(ppage) || page_has_type(ppage)) + if (!ppage) pcount = 0; else pcount = page_mapcount(ppage); @@ -124,11 +124,8 @@ u64 stable_page_flags(struct page *page) /* * pseudo flags for the well known (anonymous) memory mapped pages - * - * Note that page->_mapcount is overloaded in SLAB, so the - * simple test in page_mapped() is not enough. */ - if (!PageSlab(page) && page_mapped(page)) + if (page_mapped(page)) u |= 1 << KPF_MMAP; if (PageAnon(page)) u |= 1 << KPF_ANON; diff --git a/include/linux/mm.h b/include/linux/mm.h index 0436b919f1c7..5ff3d687bc6c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1223,14 +1223,16 @@ static inline void page_mapcount_reset(struct page *page) * a large folio, it includes the number of times this page is mapped * as part of that folio. * - * The result is undefined for pages which cannot be mapped into userspace. - * For example SLAB or special types of pages. See function page_has_type(). - * They use this field in struct page differently. + * Will report 0 for pages which cannot be mapped into userspace, eg + * slab, page tables and similar. */ static inline int page_mapcount(struct page *page) { int mapcount = atomic_read(&page->_mapcount) + 1; + /* Handle page_has_type() pages */ + if (mapcount < 0) + mapcount = 0; if (unlikely(PageCompound(page))) mapcount += folio_entire_mapcount(page_folio(page)); diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 8d0e6ce25ca2..5852f967c640 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -971,12 +971,12 @@ static inline bool is_page_hwpoison(struct page *page) * page_type may be used. Because it is initialised to -1, we invert the * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and - * low bits so that an underflow or overflow of page_mapcount() won't be + * low bits so that an underflow or overflow of _mapcount won't be * mistaken for a page type value. */ #define PAGE_TYPE_BASE 0xf0000000 -/* Reserve 0x0000007f to catch underflows of page_mapcount */ +/* Reserve 0x0000007f to catch underflows of _mapcount */ #define PAGE_MAPCOUNT_RESERVE -128 #define PG_buddy 0x00000080 #define PG_offline 0x00000100
Return 0 for pages which can't be mapped. This matches how page_mapped() works. It is more convenient for users to not have to filter out these pages. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- fs/proc/page.c | 7 ++----- include/linux/mm.h | 8 +++++--- include/linux/page-flags.h | 4 ++-- 3 files changed, 9 insertions(+), 10 deletions(-)