[PATCH RFC v2 05/27] mm: page_alloc: Add an arch hook to allow prep_new_page() to fail

Alexandru Elisei
2023-11-19T16:58:40Z

Introduce arch_prep_new_page(), which will be used by arm64 to reserve tag
storage for an allocated page. Reserving tag storage can fail, for example,
if the tag storage page has a short pin on it, so allow prep_new_page() ->
arch_prep_new_page() to similarly fail.

arch_alloc_page(), called from post_alloc_hook(), has been considered as an
alternative to adding yet another arch hook, but post_alloc_hook() cannot
fail, as it's also called when free pages are isolated.

Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
---
include/linux/pgtable.h | 7 ++++
mm/page_alloc.c | 75 ++++++++++++++++++++++++++++++++---------
2 files changed, 66 insertions(+), 16 deletions(-)

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index af7639c3b0a3..b31f53e9ab1d 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -873,6 +873,13 @@ static inline void arch_do_swap_page(struct mm_struct *mm,
}
#endif

+#ifndef __HAVE_ARCH_PREP_NEW_PAGE
+static inline int arch_prep_new_page(struct page *page, int order, gfp_t gfp)
+{
+ return 0;
+}
+#endif
+
#ifndef __HAVE_ARCH_UNMAP_ONE
/*
* Some architectures support metadata associated with a page. When a
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 770e585b77c8..b2782b778e78 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1538,9 +1538,15 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
page_table_check_alloc(page, order);
}

-static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
+static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
unsigned int alloc_flags)
{
+ int ret;
+
+ ret = arch_prep_new_page(page, order, gfp_flags);
+ if (unlikely(ret))
+ return ret;
+
post_alloc_hook(page, order, gfp_flags);

if (order && (gfp_flags & __GFP_COMP))
@@ -1556,6 +1562,8 @@ static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags
set_page_pfmemalloc(page);
else
clear_page_pfmemalloc(page);
+
+ return 0;
}

/*
@@ -3163,6 +3171,24 @@ static inline unsigned int gfp_to_alloc_flags_cma(gfp_t gfp_mask,
return alloc_flags;
}

+#ifdef HAVE_ARCH_ALLOC_PAGE
+static void return_page_to_buddy(struct page *page, int order)
+{
+ int migratetype = get_pfnblock_migratetype(page, pfn);
+ unsigned long pfn = page_to_pfn(page);
+ struct zone *zone = page_zone(page);
+ unsigned long flags;
+
+ spin_lock_irqsave(&zone->lock, flags);
+ __free_one_page(page, pfn, zone, order, migratetype, FPI_TO_TAIL);
+ spin_unlock_irqrestore(&zone->lock, flags);
+}
+#else
+static void return_page_to_buddy(struct page *page, int order)
+{
+}
+#endif
+
/*
* get_page_from_freelist goes through the zonelist trying to allocate
* a page.
@@ -3309,7 +3335,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
page = rmqueue(ac->preferred_zoneref->zone, zone, order,
gfp_mask, alloc_flags, ac->migratetype);
if (page) {
- prep_new_page(page, order, gfp_mask, alloc_flags);
+ if (prep_new_page(page, order, gfp_mask, alloc_flags)) {
+ return_page_to_buddy(page, order);
+ goto no_page;
+ }

/*
* If this is a high-order atomic allocation then check
@@ -3319,20 +3348,20 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
reserve_highatomic_pageblock(page, zone);

return page;
- } else {
- if (has_unaccepted_memory()) {
- if (try_to_accept_memory(zone, order))
- goto try_this_zone;
- }
+ }
+no_page:
+ if (has_unaccepted_memory()) {
+ if (try_to_accept_memory(zone, order))
+ goto try_this_zone;
+ }

#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
- /* Try again if zone has deferred pages */
- if (deferred_pages_enabled()) {
- if (_deferred_grow_zone(zone, order))
- goto try_this_zone;
- }
-#endif
+ /* Try again if zone has deferred pages */
+ if (deferred_pages_enabled()) {
+ if (_deferred_grow_zone(zone, order))
+ goto try_this_zone;
}
+#endif
}

/*
@@ -3538,8 +3567,12 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
count_vm_event(COMPACTSTALL);

/* Prep a captured page if available */
- if (page)
- prep_new_page(page, order, gfp_mask, alloc_flags);
+ if (page) {
+ if (prep_new_page(page, order, gfp_mask, alloc_flags)) {
+ return_page_to_buddy(page, order);
+ page = NULL;
+ }
+ }

/* Try get a page from the freelist if available */
if (!page)
@@ -4490,9 +4523,18 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
}
break;
}
+
+ if (prep_new_page(page, 0, gfp, 0)) {
+ pcp_spin_unlock(pcp);
+ pcp_trylock_finish(UP_flags);
+ return_page_to_buddy(page, 0);
+ if (!nr_account)
+ goto failed;
+ else
+ goto out_statistics;
+ }
nr_account++;

- prep_new_page(page, 0, gfp, 0);
if (page_list)
list_add(&page->lru, page_list);
else
@@ -4503,6 +4545,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid,
pcp_spin_unlock(pcp);
pcp_trylock_finish(UP_flags);

+out_statistics:
__count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account);
zone_statistics(ac.preferred_zoneref->zone, zone, nr_account);

--
2.42.1