hugetlb: batch freeing of vmemmap pages

Now that batching of hugetlb vmemmap optimization processing is possible,
batch the freeing of vmemmap pages.  When freeing vmemmap pages for a
hugetlb page, we add them to a list that is freed after the entire batch
has been processed.

This enhances the ability to return contiguous ranges of memory to the low
level allocators.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Kravetz <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Barry Song <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: James Houghton <[email protected]>
Cc: Joao Martins <[email protected]>
Cc: Konrad Dybcio <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Miaohe Lin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Usama Arif <[email protected]>
Cc: Xiongchun Duan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/hugetlb_vmemmap.c

@@ -251,7 +251,7 @@ static void vmemmap_remap_pte(pte_t *pte, unsigned long addr,
  }
 
  entry = mk_pte(walk->reuse_page, pgprot);
- list_add_tail(&page->lru, walk->vmemmap_pages);
+ list_add(&page->lru, walk->vmemmap_pages);
  set_pte_at(&init_mm, addr, pte, entry);
 }
 
@@ -306,18 +306,20 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
  * @end: end address of the vmemmap virtual address range that we want to
  * remap.
  * @reuse: reuse address.
+ * @vmemmap_pages: list to deposit vmemmap pages to be freed. It is callers
+ * responsibility to free pages.
  *
  * Return: %0 on success, negative error code otherwise.
  */
 static int vmemmap_remap_free(unsigned long start, unsigned long end,
- unsigned long reuse)
+ unsigned long reuse,
+ struct list_head *vmemmap_pages)
 {
  int ret;
- LIST_HEAD(vmemmap_pages);
  struct vmemmap_remap_walk walk = {
  .remap_pte = vmemmap_remap_pte,
  .reuse_addr = reuse,
- .vmemmap_pages = &vmemmap_pages,
+ .vmemmap_pages = vmemmap_pages,
  };
  int nid = page_to_nid((struct page *)reuse);
  gfp_t gfp_mask = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
@@ -334,7 +336,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
  if (walk.reuse_page) {
  copy_page(page_to_virt(walk.reuse_page),
  (void *)walk.reuse_addr);
- list_add(&walk.reuse_page->lru, &vmemmap_pages);
+ list_add(&walk.reuse_page->lru, vmemmap_pages);
  }
 
  /*
@@ -365,15 +367,13 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
  walk = (struct vmemmap_remap_walk) {
  .remap_pte = vmemmap_restore_pte,
  .reuse_addr = reuse,
- .vmemmap_pages = &vmemmap_pages,
+ .vmemmap_pages = vmemmap_pages,
  };
 
  vmemmap_remap_range(reuse, end, &walk);
  }
  mmap_read_unlock(&init_mm);
 
- free_vmemmap_page_list(&vmemmap_pages);
-
  return ret;
 }
 
@@ -389,7 +389,7 @@ static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
  page = alloc_pages_node(nid, gfp_mask, 0);
  if (!page)
  goto out;
- list_add_tail(&page->lru, list);
+ list_add(&page->lru, list);
  }
 
  return 0;
@@ -577,24 +577,17 @@ static bool vmemmap_should_optimize(const struct hstate *h, const struct page *h
  return true;
 }
 
-/**
- * hugetlb_vmemmap_optimize - optimize @head page's vmemmap pages.
- * @h: struct hstate.
- * @head: the head page whose vmemmap pages will be optimized.
- *
- * This function only tries to optimize @head's vmemmap pages and does not
- * guarantee that the optimization will succeed after it returns. The caller
- * can use HPageVmemmapOptimized(@head) to detect if @head's vmemmap pages
- * have been optimized.
- */
-void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
+static int __hugetlb_vmemmap_optimize(const struct hstate *h,
+ struct page *head,
+ struct list_head *vmemmap_pages)
 {
+ int ret = 0;
  unsigned long vmemmap_start = (unsigned long)head, vmemmap_end;
  unsigned long vmemmap_reuse;
 
  VM_WARN_ON_ONCE(!PageHuge(head));
  if (!vmemmap_should_optimize(h, head))
- return;
+ return ret;
 
  static_branch_inc(&hugetlb_optimize_vmemmap_key);
 
@@ -604,21 +597,58 @@ void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
 
  /*
  * Remap the vmemmap virtual address range [@vmemmap_start, @vmemmap_end)
- * to the page which @vmemmap_reuse is mapped to, then free the pages
- * which the range [@vmemmap_start, @vmemmap_end] is mapped to.
+ * to the page which @vmemmap_reuse is mapped to. Add pages previously
+ * mapping the range to vmemmap_pages list so that they can be freed by
+ * the caller.
  */
- if (vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse))
+ ret = vmemmap_remap_free(vmemmap_start, vmemmap_end, vmemmap_reuse, vmemmap_pages);
+ if (ret)
  static_branch_dec(&hugetlb_optimize_vmemmap_key);
  else
  SetHPageVmemmapOptimized(head);
+
+ return ret;
+}
+
+/**
+ * hugetlb_vmemmap_optimize - optimize @head page's vmemmap pages.
+ * @h: struct hstate.
+ * @head: the head page whose vmemmap pages will be optimized.
+ *
+ * This function only tries to optimize @head's vmemmap pages and does not
+ * guarantee that the optimization will succeed after it returns. The caller
+ * can use HPageVmemmapOptimized(@head) to detect if @head's vmemmap pages
+ * have been optimized.
+ */
+void hugetlb_vmemmap_optimize(const struct hstate *h, struct page *head)
+{
+ LIST_HEAD(vmemmap_pages);
+
+ __hugetlb_vmemmap_optimize(h, head, &vmemmap_pages);
+ free_vmemmap_page_list(&vmemmap_pages);
 }
 
 void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_list)
 {
  struct folio *folio;
+ LIST_HEAD(vmemmap_pages);
+
+ list_for_each_entry(folio, folio_list, lru) {
+ int ret = __hugetlb_vmemmap_optimize(h, &folio->page,
+ &vmemmap_pages);
+
+ /*
+ * Pages to be freed may have been accumulated. If we
+ * encounter an ENOMEM, free what we have and try again.
+ */
+ if (ret == -ENOMEM && !list_empty(&vmemmap_pages)) {
+ free_vmemmap_page_list(&vmemmap_pages);
+ INIT_LIST_HEAD(&vmemmap_pages);
+ __hugetlb_vmemmap_optimize(h, &folio->page, &vmemmap_pages);
+ }
+ }
 
- list_for_each_entry(folio, folio_list, lru)
- hugetlb_vmemmap_optimize(h, &folio->page);
+ free_vmemmap_page_list(&vmemmap_pages);
 }
 
 static struct ctl_table hugetlb_vmemmap_sysctls[] = {