+ mm-hugetlb_vmemmap-provide-stronger-vmemmap-allocation-guarantees.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: hugetlb_vmemmap: provide stronger vmemmap allocation guarantees
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hugetlb_vmemmap-provide-stronger-vmemmap-allocation-guarantees.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hugetlb_vmemmap-provide-stronger-vmemmap-allocation-guarantees.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: mm: hugetlb_vmemmap: provide stronger vmemmap allocation guarantees
Date: Mon, 8 May 2023 23:40:59 +0000

HugeTLB pages have a struct page optimizations where struct pages for tail
pages are freed.  However, when HugeTLB pages are destroyed, the memory
for struct pages (vmemmap) need to be allocated again.

Currently, __GFP_NORETRY flag is used to allocate the memory for vmemmap,
but given that this flag makes very little effort to actually reclaim
memory the returning of huge pages back to the system can be problem. 
Lets use __GFP_RETRY_MAYFAIL instead.  This flag is also performs graceful
reclaim without causing ooms, but at least it may perform a few retries,
and will fail only when there is genuinely little amount of unused memory
in the system.

Freeing a 1G page requires 16M of free memory.  A machine might need to be
reconfigured from one task to another, and release a large number of 1G
pages back to the system if allocating 16M fails, the release won't work.

Link: https://lkml.kernel.org/r/20230508234059.2529638-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Suggested-by: David Rientjes <rientjes@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb_vmemmap.c |   11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

--- a/mm/hugetlb_vmemmap.c~mm-hugetlb_vmemmap-provide-stronger-vmemmap-allocation-guarantees
+++ a/mm/hugetlb_vmemmap.c
@@ -384,8 +384,9 @@ static int vmemmap_remap_free(unsigned l
 }
 
 static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
-				   gfp_t gfp_mask, struct list_head *list)
+				   struct list_head *list)
 {
+	gfp_t gfp_mask = GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_THISNODE;
 	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
 	int nid = page_to_nid((struct page *)start);
 	struct page *page, *next;
@@ -413,12 +414,11 @@ out:
  * @end:	end address of the vmemmap virtual address range that we want to
  *		remap.
  * @reuse:	reuse address.
- * @gfp_mask:	GFP flag for allocating vmemmap pages.
  *
  * Return: %0 on success, negative error code otherwise.
  */
 static int vmemmap_remap_alloc(unsigned long start, unsigned long end,
-			       unsigned long reuse, gfp_t gfp_mask)
+			       unsigned long reuse)
 {
 	LIST_HEAD(vmemmap_pages);
 	struct vmemmap_remap_walk walk = {
@@ -430,7 +430,7 @@ static int vmemmap_remap_alloc(unsigned
 	/* See the comment in the vmemmap_remap_free(). */
 	BUG_ON(start - reuse != PAGE_SIZE);
 
-	if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
+	if (alloc_vmemmap_page_list(start, end, &vmemmap_pages))
 		return -ENOMEM;
 
 	mmap_read_lock(&init_mm);
@@ -476,8 +476,7 @@ int hugetlb_vmemmap_restore(const struct
 	 * When a HugeTLB page is freed to the buddy allocator, previously
 	 * discarded vmemmap pages must be allocated and remapping.
 	 */
-	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse,
-				  GFP_KERNEL | __GFP_NORETRY | __GFP_THISNODE);
+	ret = vmemmap_remap_alloc(vmemmap_start, vmemmap_end, vmemmap_reuse);
 	if (!ret) {
 		ClearHPageVmemmapOptimized(head);
 		static_branch_dec(&hugetlb_optimize_vmemmap_key);
_

Patches currently in -mm which might be from pasha.tatashin@soleen.com are

mm-hugetlb_vmemmap-provide-stronger-vmemmap-allocation-guarantees.patch