Re: [PATCH 1/8] xen/grant-table: Make set/clear page private code shared

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

On 05/31/2018 12:34 AM, Dongwon Kim wrote:
> On Fri, May 25, 2018 at 06:33:24PM +0300, Oleksandr Andrushchenko wrote:
> > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >
> > Make set/clear page private code shared and accessible to
> > other kernel modules which can re-use these instead of open-coding.
> >
> > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > ---
> >   drivers/xen/grant-table.c | 54 +++++++++++++++++++++++++--------------
> >   include/xen/grant_table.h |  3 +++
> >   2 files changed, 38 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> > index 27be107d6480..d7488226e1f2 100644
> > --- a/drivers/xen/grant-table.c
> > +++ b/drivers/xen/grant-table.c
> > @@ -769,29 +769,18 @@ void gnttab_free_auto_xlat_frames(void)
> >   }
> >   EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);
> >   
> > -/**
> > - * gnttab_alloc_pages - alloc pages suitable for grant mapping into
> > - * @nr_pages: number of pages to alloc
> > - * @pages: returns the pages
> > - */
> > -int gnttab_alloc_pages(int nr_pages, struct page **pages)
> > +int gnttab_pages_set_private(int nr_pages, struct page **pages)
> >   {
> >   	int i;
> > -	int ret;
> > -
> > -	ret = alloc_xenballooned_pages(nr_pages, pages);
> > -	if (ret < 0)
> > -		return ret;
> >   
> >   	for (i = 0; i < nr_pages; i++) {
> >   #if BITS_PER_LONG < 64
> >   		struct xen_page_foreign *foreign;
> >   
> >   		foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
> > -		if (!foreign) {
> > -			gnttab_free_pages(nr_pages, pages);
> > +		if (!foreign)
> Don't we have to free previously allocated "foreign"(s) if it fails in the middle
> (e.g. 0 < i && i < nr_pages - 1) before returning?
gnttab_free_pages(nr_pages, pages); will take care of it when called from
outside, see below. It can also handle partial allocations, so no problem
here
> >   			return -ENOMEM;
> > -		}
> > +
> >   		set_page_private(pages[i], (unsigned long)foreign);
> >   #endif
> >   		SetPagePrivate(pages[i]);
> > @@ -799,14 +788,30 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages)
> >   
> >   	return 0;
> >   }
> > -EXPORT_SYMBOL(gnttab_alloc_pages);
> > +EXPORT_SYMBOL(gnttab_pages_set_private);
> >   
> >   /**
> > - * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
> > - * @nr_pages; number of pages to free
> > - * @pages: the pages
> > + * gnttab_alloc_pages - alloc pages suitable for grant mapping into
> > + * @nr_pages: number of pages to alloc
> > + * @pages: returns the pages
> >    */
> > -void gnttab_free_pages(int nr_pages, struct page **pages)
> > +int gnttab_alloc_pages(int nr_pages, struct page **pages)
> > +{
> > +	int ret;
> > +
> > +	ret = alloc_xenballooned_pages(nr_pages, pages);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	ret = gnttab_pages_set_private(nr_pages, pages);
> > +	if (ret < 0)
> > +		gnttab_free_pages(nr_pages, pages);
> > +
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(gnttab_alloc_pages);
> > +
> > +void gnttab_pages_clear_private(int nr_pages, struct page **pages)
> >   {
> >   	int i;
> >   
> > @@ -818,6 +823,17 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
> >   			ClearPagePrivate(pages[i]);
> >   		}
> >   	}
> > +}
> > +EXPORT_SYMBOL(gnttab_pages_clear_private);
> > +
> > +/**
> > + * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
> > + * @nr_pages; number of pages to free
> > + * @pages: the pages
> > + */
> > +void gnttab_free_pages(int nr_pages, struct page **pages)
> > +{
> > +	gnttab_pages_clear_private(nr_pages, pages);
> >   	free_xenballooned_pages(nr_pages, pages);
> >   }
> >   EXPORT_SYMBOL(gnttab_free_pages);
> > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> > index 2e37741f6b8d..de03f2542bb7 100644
> > --- a/include/xen/grant_table.h
> > +++ b/include/xen/grant_table.h
> > @@ -198,6 +198,9 @@ void gnttab_free_auto_xlat_frames(void);
> >   int gnttab_alloc_pages(int nr_pages, struct page **pages);
> >   void gnttab_free_pages(int nr_pages, struct page **pages);
> >   
> > +int gnttab_pages_set_private(int nr_pages, struct page **pages);
> > +void gnttab_pages_clear_private(int nr_pages, struct page **pages);
> > +
> >   int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
> >   		    struct gnttab_map_grant_ref *kmap_ops,
> >   		    struct page **pages, unsigned int count);
> > --
> > 2.17.0