Hi Matthew
On Sat, Apr 10, 2021 at 04:48:24PM +0100, Matthew Wilcox wrote:
> On Sat, Apr 10, 2021 at 12:37:58AM +0200, Matteo Croce wrote:
> > This is needed by the page_pool to avoid recycling a page not allocated
> > via page_pool.
>
> Is the PageType mechanism more appropriate to your needs? It wouldn't
> be if you use page->_mapcount (ie mapping it to userspace).
Interesting!
Please keep in mind this was written ~2018 and was stale on my branches for
quite some time. So back then I did try to use PageType, but had not free
bits. Looking at it again though, it's cleaned up. So yes I think this can
be much much cleaner. Should we go and define a new PG_pagepool?
Thanks!
/Ilias
>
> > Signed-off-by: Matteo Croce <mcroce@xxxxxxxxxxxxx>
> > ---
> > include/linux/mm_types.h | 1 +
> > include/net/page_pool.h | 2 ++
> > net/core/page_pool.c | 4 ++++
> > 3 files changed, 7 insertions(+)
> >
> > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> > index 6613b26a8894..ef2d0d5f62e4 100644
> > --- a/include/linux/mm_types.h
> > +++ b/include/linux/mm_types.h
> > @@ -101,6 +101,7 @@ struct page {
> > * 32-bit architectures.
> > */
> > dma_addr_t dma_addr;
> > + unsigned long signature;
> > };
> > struct { /* slab, slob and slub */
> > union {
> > diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> > index b5b195305346..b30405e84b5e 100644
> > --- a/include/net/page_pool.h
> > +++ b/include/net/page_pool.h
> > @@ -63,6 +63,8 @@
> > */
> > #define PP_ALLOC_CACHE_SIZE 128
> > #define PP_ALLOC_CACHE_REFILL 64
> > +#define PP_SIGNATURE 0x20210303
> > +
> > struct pp_alloc_cache {
> > u32 count;
> > void *cache[PP_ALLOC_CACHE_SIZE];
> > diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> > index ad8b0707af04..2ae9b554ef98 100644
> > --- a/net/core/page_pool.c
> > +++ b/net/core/page_pool.c
> > @@ -232,6 +232,8 @@ static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
> > page_pool_dma_sync_for_device(pool, page, pool->p.max_len);
> >
> > skip_dma_map:
> > + page->signature = PP_SIGNATURE;
> > +
> > /* Track how many pages are held 'in-flight' */
> > pool->pages_state_hold_cnt++;
> >
> > @@ -302,6 +304,8 @@ void page_pool_release_page(struct page_pool *pool, struct page *page)
> > DMA_ATTR_SKIP_CPU_SYNC);
> > page->dma_addr = 0;
> > skip_dma_unmap:
> > + page->signature = 0;
> > +
> > /* This may be the last page returned, releasing the pool, so
> > * it is not safe to reference pool afterwards.
> > */
> > --
> > 2.30.2
> >
