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-rw-r--r--Documentation/admin-guide/mm/hugetlbpage.rst8
-rw-r--r--Documentation/admin-guide/mm/memory-hotplug.rst13
-rw-r--r--include/linux/hugetlb.h3
-rw-r--r--include/linux/mm.h2
-rw-r--r--mm/hugetlb.c98
-rw-r--r--mm/hugetlb_vmemmap.c34
-rw-r--r--mm/hugetlb_vmemmap.h6
-rw-r--r--mm/migrate.c5
-rw-r--r--mm/sparse-vmemmap.c75
9 files changed, 227 insertions, 17 deletions
diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst
index f7b1c7462991..6988895d09a8 100644
--- a/Documentation/admin-guide/mm/hugetlbpage.rst
+++ b/Documentation/admin-guide/mm/hugetlbpage.rst
@@ -60,6 +60,10 @@ HugePages_Surp
the pool above the value in ``/proc/sys/vm/nr_hugepages``. The
maximum number of surplus huge pages is controlled by
``/proc/sys/vm/nr_overcommit_hugepages``.
+ Note: When the feature of freeing unused vmemmap pages associated
+ with each hugetlb page is enabled, the number of surplus huge pages
+ may be temporarily larger than the maximum number of surplus huge
+ pages when the system is under memory pressure.
Hugepagesize
is the default hugepage size (in Kb).
Hugetlb
@@ -80,6 +84,10 @@ returned to the huge page pool when freed by a task. A user with root
privileges can dynamically allocate more or free some persistent huge pages
by increasing or decreasing the value of ``nr_hugepages``.
+Note: When the feature of freeing unused vmemmap pages associated with each
+hugetlb page is enabled, we can fail to free the huge pages triggered by
+the user when ths system is under memory pressure. Please try again later.
+
Pages that are used as huge pages are reserved inside the kernel and cannot
be used for other purposes. Huge pages cannot be swapped out under
memory pressure.
diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
index 05d51d2d8beb..c6bae2d77160 100644
--- a/Documentation/admin-guide/mm/memory-hotplug.rst
+++ b/Documentation/admin-guide/mm/memory-hotplug.rst
@@ -357,6 +357,19 @@ creates ZONE_MOVABLE as following.
Unfortunately, there is no information to show which memory block belongs
to ZONE_MOVABLE. This is TBD.
+ Memory offlining can fail when dissolving a free huge page on ZONE_MOVABLE
+ and the feature of freeing unused vmemmap pages associated with each hugetlb
+ page is enabled.
+
+ This can happen when we have plenty of ZONE_MOVABLE memory, but not enough
+ kernel memory to allocate vmemmmap pages. We may even be able to migrate
+ huge page contents, but will not be able to dissolve the source huge page.
+ This will prevent an offline operation and is unfortunate as memory offlining
+ is expected to succeed on movable zones. Users that depend on memory hotplug
+ to succeed for movable zones should carefully consider whether the memory
+ savings gained from this feature are worth the risk of possibly not being
+ able to offline memory in certain situations.
+
.. note::
Techniques that rely on long-term pinnings of memory (especially, RDMA and
vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 0c8c96481259..3578d9d708fe 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -532,12 +532,14 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
* modifications require hugetlb_lock.
* HPG_freed - Set when page is on the free lists.
* Synchronization: hugetlb_lock held for examination and modification.
+ * HPG_vmemmap_optimized - Set when the vmemmap pages of the page are freed.
*/
enum hugetlb_page_flags {
HPG_restore_reserve = 0,
HPG_migratable,
HPG_temporary,
HPG_freed,
+ HPG_vmemmap_optimized,
__NR_HPAGEFLAGS,
};
@@ -583,6 +585,7 @@ HPAGEFLAG(RestoreReserve, restore_reserve)
HPAGEFLAG(Migratable, migratable)
HPAGEFLAG(Temporary, temporary)
HPAGEFLAG(Freed, freed)
+HPAGEFLAG(VmemmapOptimized, vmemmap_optimized)
#ifdef CONFIG_HUGETLB_PAGE
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3437aa7c6c91..706bee98d965 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3078,6 +3078,8 @@ static inline void print_vma_addr(char *prefix, unsigned long rip)
void vmemmap_remap_free(unsigned long start, unsigned long end,
unsigned long reuse);
+int vmemmap_remap_alloc(unsigned long start, unsigned long end,
+ unsigned long reuse, gfp_t gfp_mask);
void *sparse_buffer_alloc(unsigned long size);
struct page * __populate_section_memmap(unsigned long pfn,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e7eb1ab8c78a..778db5de6232 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1376,6 +1376,39 @@ static void remove_hugetlb_page(struct hstate *h, struct page *page,
h->nr_huge_pages_node[nid]--;
}
+static void add_hugetlb_page(struct hstate *h, struct page *page,
+ bool adjust_surplus)
+{
+ int zeroed;
+ int nid = page_to_nid(page);
+
+ VM_BUG_ON_PAGE(!HPageVmemmapOptimized(page), page);
+
+ lockdep_assert_held(&hugetlb_lock);
+
+ INIT_LIST_HEAD(&page->lru);
+ h->nr_huge_pages++;
+ h->nr_huge_pages_node[nid]++;
+
+ if (adjust_surplus) {
+ h->surplus_huge_pages++;
+ h->surplus_huge_pages_node[nid]++;
+ }
+
+ set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
+ set_page_private(page, 0);
+ SetHPageVmemmapOptimized(page);
+
+ /*
+ * This page is now managed by the hugetlb allocator and has
+ * no users -- drop the last reference.
+ */
+ zeroed = put_page_testzero(page);
+ VM_BUG_ON_PAGE(!zeroed, page);
+ arch_clear_hugepage_flags(page);
+ enqueue_huge_page(h, page);
+}
+
static void __update_and_free_page(struct hstate *h, struct page *page)
{
int i;
@@ -1384,6 +1417,18 @@ static void __update_and_free_page(struct hstate *h, struct page *page)
if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
return;
+ if (alloc_huge_page_vmemmap(h, page)) {
+ spin_lock_irq(&hugetlb_lock);
+ /*
+ * If we cannot allocate vmemmap pages, just refuse to free the
+ * page and put the page back on the hugetlb free list and treat
+ * as a surplus page.
+ */
+ add_hugetlb_page(h, page, true);
+ spin_unlock_irq(&hugetlb_lock);
+ return;
+ }
+
for (i = 0; i < pages_per_huge_page(h);
i++, subpage = mem_map_next(subpage, page, i)) {
subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
@@ -1450,7 +1495,7 @@ static inline void flush_free_hpage_work(struct hstate *h)
static void update_and_free_page(struct hstate *h, struct page *page,
bool atomic)
{
- if (!free_vmemmap_pages_per_hpage(h) || !atomic) {
+ if (!HPageVmemmapOptimized(page) || !atomic) {
__update_and_free_page(h, page);
return;
}
@@ -1806,10 +1851,14 @@ static struct page *remove_pool_huge_page(struct hstate *h,
* nothing for in-use hugepages and non-hugepages.
* This function returns values like below:
*
- * -EBUSY: failed to dissolved free hugepages or the hugepage is in-use
- * (allocated or reserved.)
- * 0: successfully dissolved free hugepages or the page is not a
- * hugepage (considered as already dissolved)
+ * -ENOMEM: failed to allocate vmemmap pages to free the freed hugepages
+ * when the system is under memory pressure and the feature of
+ * freeing unused vmemmap pages associated with each hugetlb page
+ * is enabled.
+ * -EBUSY: failed to dissolved free hugepages or the hugepage is in-use
+ * (allocated or reserved.)
+ * 0: successfully dissolved free hugepages or the page is not a
+ * hugepage (considered as already dissolved)
*/
int dissolve_free_huge_page(struct page *page)
{
@@ -1851,19 +1900,38 @@ retry:
goto retry;
}
- /*
- * Move PageHWPoison flag from head page to the raw error page,
- * which makes any subpages rather than the error page reusable.
- */
- if (PageHWPoison(head) && page != head) {
- SetPageHWPoison(page);
- ClearPageHWPoison(head);
- }
remove_hugetlb_page(h, head, false);
h->max_huge_pages--;
spin_unlock_irq(&hugetlb_lock);
- update_and_free_page(h, head, false);
- return 0;
+
+ /*
+ * Normally update_and_free_page will allocate required vmemmmap
+ * before freeing the page. update_and_free_page will fail to
+ * free the page if it can not allocate required vmemmap. We
+ * need to adjust max_huge_pages if the page is not freed.
+ * Attempt to allocate vmemmmap here so that we can take
+ * appropriate action on failure.
+ */
+ rc = alloc_huge_page_vmemmap(h, head);
+ if (!rc) {
+ /*
+ * Move PageHWPoison flag from head page to the raw
+ * error page, which makes any subpages rather than
+ * the error page reusable.
+ */
+ if (PageHWPoison(head) && page != head) {
+ SetPageHWPoison(page);
+ ClearPageHWPoison(head);
+ }
+ update_and_free_page(h, head, false);
+ } else {
+ spin_lock_irq(&hugetlb_lock);
+ add_hugetlb_page(h, head, false);
+ h->max_huge_pages++;
+ spin_unlock_irq(&hugetlb_lock);
+ }
+
+ return rc;
}
out:
spin_unlock_irq(&hugetlb_lock);
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index cb28c5b6c9ff..a897c7778246 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -185,6 +185,38 @@ static inline unsigned long free_vmemmap_pages_size_per_hpage(struct hstate *h)
return (unsigned long)free_vmemmap_pages_per_hpage(h) << PAGE_SHIFT;
}
+/*
+ * Previously discarded vmemmap pages will be allocated and remapping
+ * after this function returns zero.
+ */
+int alloc_huge_page_vmemmap(struct hstate *h, struct page *head)
+{
+ int ret;
+ unsigned long vmemmap_addr = (unsigned long)head;
+ unsigned long vmemmap_end, vmemmap_reuse;
+
+ if (!HPageVmemmapOptimized(head))
+ return 0;
+
+ vmemmap_addr += RESERVE_VMEMMAP_SIZE;
+ vmemmap_end = vmemmap_addr + free_vmemmap_pages_size_per_hpage(h);
+ vmemmap_reuse = vmemmap_addr - PAGE_SIZE;
+ /*
+ * The pages which the vmemmap virtual address range [@vmemmap_addr,
+ * @vmemmap_end) are mapped to are freed to the buddy allocator, and
+ * the range is mapped to the page which @vmemmap_reuse is mapped to.
+ * When a HugeTLB page is freed to the buddy allocator, previously
+ * discarded vmemmap pages must be allocated and remapping.
+ */
+ ret = vmemmap_remap_alloc(vmemmap_addr, vmemmap_end, vmemmap_reuse,
+ GFP_KERNEL | __GFP_NORETRY | __GFP_THISNODE);
+
+ if (!ret)
+ ClearHPageVmemmapOptimized(head);
+
+ return ret;
+}
+
void free_huge_page_vmemmap(struct hstate *h, struct page *head)
{
unsigned long vmemmap_addr = (unsigned long)head;
@@ -203,4 +235,6 @@ void free_huge_page_vmemmap(struct hstate *h, struct page *head)
* which the range [@vmemmap_addr, @vmemmap_end] is mapped to.
*/
vmemmap_remap_free(vmemmap_addr, vmemmap_end, vmemmap_reuse);
+
+ SetHPageVmemmapOptimized(head);
}
diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
index 01f8637adbe0..a37771b0b82a 100644
--- a/mm/hugetlb_vmemmap.h
+++ b/mm/hugetlb_vmemmap.h
@@ -11,6 +11,7 @@
#include <linux/hugetlb.h>
#ifdef CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
+int alloc_huge_page_vmemmap(struct hstate *h, struct page *head);
void free_huge_page_vmemmap(struct hstate *h, struct page *head);
/*
@@ -25,6 +26,11 @@ static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
return 0;
}
#else
+static inline int alloc_huge_page_vmemmap(struct hstate *h, struct page *head)
+{
+ return 0;
+}
+
static inline void free_huge_page_vmemmap(struct hstate *h, struct page *head)
{
}
diff --git a/mm/migrate.c b/mm/migrate.c
index 380ca57b9031..cc4d6af41683 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -626,7 +626,10 @@ void migrate_page_states(struct page *newpage, struct page *page)
if (PageSwapCache(page))
ClearPageSwapCache(page);
ClearPagePrivate(page);
- set_page_private(page, 0);
+
+ /* page->private contains hugetlb specific flags */
+ if (!PageHuge(page))
+ set_page_private(page, 0);
/*
* If any waiters have accumulated on the new page then
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 3ec5488c815c..a3aa275e2668 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -40,7 +40,8 @@
* @remap_pte: called for each lowest-level entry (PTE).
* @reuse_page: the page which is reused for the tail vmemmap pages.
* @reuse_addr: the virtual address of the @reuse_page page.
- * @vmemmap_pages: the list head of the vmemmap pages that can be freed.
+ * @vmemmap_pages: the list head of the vmemmap pages that can be freed
+ * or is mapped from.
*/
struct vmemmap_remap_walk {
void (*remap_pte)(pte_t *pte, unsigned long addr,
@@ -224,6 +225,78 @@ void vmemmap_remap_free(unsigned long start, unsigned long end,
free_vmemmap_page_list(&vmemmap_pages);
}
+static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
+ struct vmemmap_remap_walk *walk)
+{
+ pgprot_t pgprot = PAGE_KERNEL;
+ struct page *page;
+ void *to;
+
+ BUG_ON(pte_page(*pte) != walk->reuse_page);
+
+ page = list_first_entry(walk->vmemmap_pages, struct page, lru);
+ list_del(&page->lru);
+ to = page_to_virt(page);
+ copy_page(to, (void *)walk->reuse_addr);
+
+ set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
+}
+
+static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
+ gfp_t gfp_mask, struct list_head *list)
+{
+ unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
+ int nid = page_to_nid((struct page *)start);
+ struct page *page, *next;
+
+ while (nr_pages--) {
+ page = alloc_pages_node(nid, gfp_mask, 0);
+ if (!page)
+ goto out;
+ list_add_tail(&page->lru, list);
+ }
+
+ return 0;
+out:
+ list_for_each_entry_safe(page, next, list, lru)
+ __free_pages(page, 0);
+ return -ENOMEM;
+}
+
+/**
+ * vmemmap_remap_alloc - remap the vmemmap virtual address range [@start, end)
+ * to the page which is from the @vmemmap_pages
+ * respectively.
+ * @start: start address of the vmemmap virtual address range that we want
+ * to remap.
+ * @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.
+ */
+int vmemmap_remap_alloc(unsigned long start, unsigned long end,
+ unsigned long reuse, gfp_t gfp_mask)
+{
+ LIST_HEAD(vmemmap_pages);
+ struct vmemmap_remap_walk walk = {
+ .remap_pte = vmemmap_restore_pte,
+ .reuse_addr = reuse,
+ .vmemmap_pages = &vmemmap_pages,
+ };
+
+ /* See the comment in the vmemmap_remap_free(). */
+ BUG_ON(start - reuse != PAGE_SIZE);
+
+ might_sleep_if(gfpflags_allow_blocking(gfp_mask));
+
+ if (alloc_vmemmap_page_list(start, end, gfp_mask, &vmemmap_pages))
+ return -ENOMEM;
+
+ vmemmap_remap_range(reuse, end, &walk);
+
+ return 0;
+}
+
/*
* Allocate a block of memory to be used to back the virtual memory map
* or to back the page tables that are used to create the mapping.
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-22 22:40:29 +0300