| Message ID | 20190625075227.15193-4-osalvador@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Allocate memmap from hotadded memory | expand |
On 25.06.19 09:52, Oscar Salvador wrote: > Introduce a set of functions for Vmemmap pages. > Set of functions: > > - {Set,Clear,Check} Vmemmap flag > - Given a vmemmap page, get its vmemmap-head > - Get #nr of vmemmap pages taking into account the current position > of the page > > These functions will be used for the code handling Vmemmap pages. > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > --- > include/linux/page-flags.h | 34 ++++++++++++++++++++++++++++++++++ > mm/util.c | 2 ++ > 2 files changed, 36 insertions(+) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index b848517da64c..a8b9b57162b3 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -466,6 +466,40 @@ static __always_inline int __PageMovable(struct page *page) > PAGE_MAPPING_MOVABLE; > } > > +#define VMEMMAP_PAGE (~PAGE_MAPPING_FLAGS) > +static __always_inline int PageVmemmap(struct page *page) > +{ > + return PageReserved(page) && (unsigned long)page->mapping == VMEMMAP_PAGE; > +} > + > +static __always_inline int __PageVmemmap(struct page *page) > +{ > + return (unsigned long)page->mapping == VMEMMAP_PAGE; > +} > + > +static __always_inline void __ClearPageVmemmap(struct page *page) > +{ Should we VM_BUG_ON in case !PG_reserved || pg->mapping != VMEMMAP_PAGE ? > + __ClearPageReserved(page); > + page->mapping = NULL; > +} > + > +static __always_inline void __SetPageVmemmap(struct page *page) > +{ Should we VM_BUG_ON in case PG_reserved || pg->mapping != NULL ? > + __SetPageReserved(page); > + page->mapping = (void *)VMEMMAP_PAGE; > +} > + > +static __always_inline struct page *vmemmap_get_head(struct page *page) > +{ > + return (struct page *)page->freelist; freelist is a "slab, slob and slub" concept (reading include/linux/mm_types.h). page->mapping is a "Page cache and anonymous pages" concept. Hmmm... > +} > + > +static __always_inline unsigned long get_nr_vmemmap_pages(struct page *page) > +{ > + struct page *head = vmemmap_get_head(page); > + return head->private - (page - head); > +} > + > #ifdef CONFIG_KSM > /* > * A KSM page is one of those write-protected "shared pages" or "merged pages" > diff --git a/mm/util.c b/mm/util.c > index 021648a8a3a3..5e20563cdef6 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -607,6 +607,8 @@ struct address_space *page_mapping(struct page *page) > mapping = page->mapping; > if ((unsigned long)mapping & PAGE_MAPPING_ANON) > return NULL; > + if ((unsigned long)mapping == VMEMMAP_PAGE) > + return NULL; > > return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS); > } > I wonder if using a page type would be appropriate here instead. Then, define a new sub-structure within "struct page" that describes what you actually want (instead of reusing ->private and ->mapping). Just an idea, we have to find out if that is possible. vmemmap_get_head() smells like __GFP_COMP, but of course, these vmemmap pages never saw the buddy. But sounds like you want a similar concept.
On Tue, Jun 25, 2019 at 12:28:56PM +0200, David Hildenbrand wrote: > > +static __always_inline void __ClearPageVmemmap(struct page *page) > > +{ > > Should we VM_BUG_ON in case !PG_reserved || pg->mapping != VMEMMAP_PAGE ? We can do that, just for extra protection. > > > + __ClearPageReserved(page); > > + page->mapping = NULL; > > +} > > + > > +static __always_inline void __SetPageVmemmap(struct page *page) > > +{ > > Should we VM_BUG_ON in case PG_reserved || pg->mapping != NULL ? ditto. > > > + __SetPageReserved(page); > > + page->mapping = (void *)VMEMMAP_PAGE; > > +} > > + > > +static __always_inline struct page *vmemmap_get_head(struct page *page) > > +{ > > + return (struct page *)page->freelist; > > freelist is a "slab, slob and slub" concept (reading > include/linux/mm_types.h). page->mapping is a "Page cache and anonymous > pages" concept. Hmmm... Yeah. In an early stage, I thought about constructing vmemmap pages the same way we construct compound pages, so we can leverage the APIs that we already have. For some reason I did not go further with that, but I will investigate in that direction. > I wonder if using a page type would be appropriate here instead. Then, > define a new sub-structure within "struct page" that describes what you > actually want (instead of reusing ->private and ->mapping). Just an > idea, we have to find out if that is possible. > > vmemmap_get_head() smells like __GFP_COMP, but of course, these vmemmap > pages never saw the buddy. But sounds like you want a similar concept. Thanks for the feedback. I will take a look at it.
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index b848517da64c..a8b9b57162b3 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -466,6 +466,40 @@ static __always_inline int __PageMovable(struct page *page) PAGE_MAPPING_MOVABLE; } +#define VMEMMAP_PAGE (~PAGE_MAPPING_FLAGS) +static __always_inline int PageVmemmap(struct page *page) +{ + return PageReserved(page) && (unsigned long)page->mapping == VMEMMAP_PAGE; +} + +static __always_inline int __PageVmemmap(struct page *page) +{ + return (unsigned long)page->mapping == VMEMMAP_PAGE; +} + +static __always_inline void __ClearPageVmemmap(struct page *page) +{ + __ClearPageReserved(page); + page->mapping = NULL; +} + +static __always_inline void __SetPageVmemmap(struct page *page) +{ + __SetPageReserved(page); + page->mapping = (void *)VMEMMAP_PAGE; +} + +static __always_inline struct page *vmemmap_get_head(struct page *page) +{ + return (struct page *)page->freelist; +} + +static __always_inline unsigned long get_nr_vmemmap_pages(struct page *page) +{ + struct page *head = vmemmap_get_head(page); + return head->private - (page - head); +} + #ifdef CONFIG_KSM /* * A KSM page is one of those write-protected "shared pages" or "merged pages" diff --git a/mm/util.c b/mm/util.c index 021648a8a3a3..5e20563cdef6 100644 --- a/mm/util.c +++ b/mm/util.c @@ -607,6 +607,8 @@ struct address_space *page_mapping(struct page *page) mapping = page->mapping; if ((unsigned long)mapping & PAGE_MAPPING_ANON) return NULL; + if ((unsigned long)mapping == VMEMMAP_PAGE) + return NULL; return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS); }
Introduce a set of functions for Vmemmap pages. Set of functions: - {Set,Clear,Check} Vmemmap flag - Given a vmemmap page, get its vmemmap-head - Get #nr of vmemmap pages taking into account the current position of the page These functions will be used for the code handling Vmemmap pages. Signed-off-by: Oscar Salvador <osalvador@suse.de> --- include/linux/page-flags.h | 34 ++++++++++++++++++++++++++++++++++ mm/util.c | 2 ++ 2 files changed, 36 insertions(+)