On Wed 24-07-24 20:55:40, Barry Song wrote: > From: Barry Song <[email protected]> > > mm doesn't support non-blockable __GFP_NOFAIL allocation. Because > __GFP_NOFAIL without direct reclamation may just result in a busy > loop within non-sleepable contexts. > > static inline struct page * > __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > struct alloc_context *ac) > { > ... > /* > * Make sure that __GFP_NOFAIL request doesn't leak out and make sure > * we always retry > */ > if (gfp_mask & __GFP_NOFAIL) { > /* > * All existing users of the __GFP_NOFAIL are blockable, so > warn > * of any new users that actually require GFP_NOWAIT > */ > if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask)) > goto fail; > ... > } > ... > fail: > warn_alloc(gfp_mask, ac->nodemask, > "page allocation failure: order:%u", order); > got_pg: > return page; > } > > Let's move the memory allocation out of the atomic context and use > the normal sleepable context to get pages. > > [RFC]: This has only been compile-tested; I'd prefer if the VDPA maintainers > handles it. > > Cc: "Michael S. Tsirkin" <[email protected]> > Cc: Jason Wang <[email protected]> > Cc: Xuan Zhuo <[email protected]> > Cc: "Eugenio Pérez" <[email protected]> > Cc: Maxime Coquelin <[email protected]> > Signed-off-by: Barry Song <[email protected]> > --- > drivers/vdpa/vdpa_user/iova_domain.c | 24 ++++++++++++++++++++---- > 1 file changed, 20 insertions(+), 4 deletions(-) > > diff --git a/drivers/vdpa/vdpa_user/iova_domain.c > b/drivers/vdpa/vdpa_user/iova_domain.c > index 791d38d6284c..eff700e5f7a2 100644 > --- a/drivers/vdpa/vdpa_user/iova_domain.c > +++ b/drivers/vdpa/vdpa_user/iova_domain.c > @@ -287,28 +287,44 @@ void vduse_domain_remove_user_bounce_pages(struct > vduse_iova_domain *domain) > { > struct vduse_bounce_map *map; > unsigned long i, count; > + struct page **pages = NULL; > > write_lock(&domain->bounce_lock); > if (!domain->user_bounce_pages) > goto out; > - > count = domain->bounce_size >> PAGE_SHIFT; > + write_unlock(&domain->bounce_lock); > + > + pages = kmalloc_array(count, sizeof(*pages), GFP_KERNEL | __GFP_NOFAIL); > + for (i = 0; i < count; i++) > + pages[i] = alloc_page(GFP_KERNEL | __GFP_NOFAIL);
AFAICS vduse_domain_release calls this function with spin_lock(&domain->iotlb_lock) so dropping &domain->bounce_lock is not sufficient. -- Michal Hocko SUSE Labs
