mm/hugetlb: wait for hugetlb folios to be freed

[ Upstream commit 67bab13307c83fb742c2556b06cdc39dbad27f07 ]

Since the introduction of commit c77c0a8ac4c52 ("mm/hugetlb: defer freeing
of huge pages if in non-task context"), which supports deferring the
freeing of hugetlb pages, the allocation of contiguous memory through
cma_alloc() may fail probabilistically.

In the CMA allocation process, if it is found that the CMA area is
occupied by in-use hugetlb folios, these in-use hugetlb folios need to be
migrated to another location.  When there are no available hugetlb folios
in the free hugetlb pool during the migration of in-use hugetlb folios,
new folios are allocated from the buddy system.  A temporary state is set
on the newly allocated folio.  Upon completion of the hugetlb folio
migration, the temporary state is transferred from the new folios to the
old folios.  Normally, when the old folios with the temporary state are
freed, it is directly released back to the buddy system.  However, due to
the deferred freeing of hugetlb pages, the PageBuddy() check fails,
ultimately leading to the failure of cma_alloc().

Here is a simplified call trace illustrating the process:
cma_alloc()
    ->__alloc_contig_migrate_range() // Migrate in-use hugetlb folios
        ->unmap_and_move_huge_page()
            ->folio_putback_hugetlb() // Free old folios
    ->test_pages_isolated()
        ->__test_page_isolated_in_pageblock()
             ->PageBuddy(page) // Check if the page is in buddy

To resolve this issue, we have implemented a function named
wait_for_freed_hugetlb_folios().  This function ensures that the hugetlb
folios are properly released back to the buddy system after their
migration is completed.  By invoking wait_for_freed_hugetlb_folios()
before calling PageBuddy(), we ensure that PageBuddy() will succeed.

Link: https://lkml.kernel.org/r/1739936804-18199-1-git-send-email-yangge1116@126.com
Fixes: c77c0a8ac4c5 ("mm/hugetlb: defer freeing of huge pages if in non-task context")
Signed-off-by: Ge Yang <yangge1116@126.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <21cnbao@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 25a7b13574c28b8f9b8932aed56d164028f65fe1..12f7a7b9c06e9bdaccea68ffa93c8343a78a940a 100644 (file)
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -687,6 +687,7 @@ struct huge_bootmem_page {
 };
 
 int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list);
+void wait_for_freed_hugetlb_folios(void);
 struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
                                unsigned long addr, int avoid_reserve);
 struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid,
@@ -1057,6 +1058,10 @@ static inline int isolate_or_dissolve_huge_page(struct page *page,
        return -ENOMEM;
 }
 
+static inline void wait_for_freed_hugetlb_folios(void)
+{
+}
+
 static inline struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
                                           unsigned long addr,
                                           int avoid_reserve)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1e9aa6de4e21ea743962a635e49af8176071b9e2..e28e820fdb7756f6d71db2dd43aa9247b0099670 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2955,6 +2955,14 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
        return ret;
 }
 
+void wait_for_freed_hugetlb_folios(void)
+{
+       if (llist_empty(&hpage_freelist))
+               return;
+
+       flush_work(&free_hpage_work);
+}
+
 struct folio *alloc_hugetlb_folio(struct vm_area_struct *vma,
                                    unsigned long addr, int avoid_reserve)
 {

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 7e04047977cfea54e860b80d992758f2daf7fe5d..6989c5ffd4741741dd704e7a00cb8d5a97a12fc1 100644 (file)
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -611,6 +611,16 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
        struct zone *zone;
        int ret;
 
+       /*
+        * Due to the deferred freeing of hugetlb folios, the hugepage folios may
+        * not immediately release to the buddy system. This can cause PageBuddy()
+        * to fail in __test_page_isolated_in_pageblock(). To ensure that the
+        * hugetlb folios are properly released back to the buddy system, we
+        * invoke the wait_for_freed_hugetlb_folios() function to wait for the
+        * release to complete.
+        */
+       wait_for_freed_hugetlb_folios();
+
        /*
         * Note: pageblock_nr_pages != MAX_PAGE_ORDER. Then, chunks of free
         * pages are not aligned to pageblock_nr_pages.