The patch titled
Subject: mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page-fix
has been removed from the -mm tree. Its filename was
mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page-fix.patch
This patch was dropped because it was folded into mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page.patch
------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page-fix
restore lost comment changes
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
Cc: Joao Martins <joao.m.martins@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb_vmemmap.c | 42 +++++++++++++++++++++++------------------
1 file changed, 24 insertions(+), 18 deletions(-)
--- a/mm/hugetlb_vmemmap.c~mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page-fix
+++ a/mm/hugetlb_vmemmap.c
@@ -124,9 +124,9 @@
* page of page structs (page 0) associated with the HugeTLB page contains the 4
* page structs necessary to describe the HugeTLB. The only use of the remaining
* pages of page structs (page 1 to page 7) is to point to page->compound_head.
- * Therefore, we can remap pages 2 to 7 to page 1. Only 2 pages of page structs
+ * Therefore, we can remap pages 1 to 7 to page 0. Only 1 page of page structs
* will be used for each HugeTLB page. This will allow us to free the remaining
- * 6 pages to the buddy allocator.
+ * 7 pages to the buddy allocator.
*
* Here is how things look after remapping.
*
@@ -134,30 +134,30 @@
* +-----------+ ---virt_to_page---> +-----------+ mapping to +-----------+
* | | | 0 | -------------> | 0 |
* | | +-----------+ +-----------+
- * | | | 1 | -------------> | 1 |
- * | | +-----------+ +-----------+
- * | | | 2 | ----------------^ ^ ^ ^ ^ ^
- * | | +-----------+ | | | | |
- * | | | 3 | ------------------+ | | | |
- * | | +-----------+ | | | |
- * | | | 4 | --------------------+ | | |
- * | PMD | +-----------+ | | |
- * | level | | 5 | ----------------------+ | |
- * | mapping | +-----------+ | |
- * | | | 6 | ------------------------+ |
- * | | +-----------+ |
- * | | | 7 | --------------------------+
+ * | | | 1 | ---------------^ ^ ^ ^ ^ ^ ^
+ * | | +-----------+ | | | | | |
+ * | | | 2 | -----------------+ | | | | |
+ * | | +-----------+ | | | | |
+ * | | | 3 | -------------------+ | | | |
+ * | | +-----------+ | | | |
+ * | | | 4 | ---------------------+ | | |
+ * | PMD | +-----------+ | | |
+ * | level | | 5 | -----------------------+ | |
+ * | mapping | +-----------+ | |
+ * | | | 6 | -------------------------+ |
+ * | | +-----------+ |
+ * | | | 7 | ---------------------------+
* | | +-----------+
* | |
* | |
* | |
* +-----------+
*
- * When a HugeTLB is freed to the buddy system, we should allocate 6 pages for
+ * When a HugeTLB is freed to the buddy system, we should allocate 7 pages for
* vmemmap pages and restore the previous mapping relationship.
*
* For the HugeTLB page of the pud level mapping. It is similar to the former.
- * We also can use this approach to free (PAGE_SIZE - 2) vmemmap pages.
+ * We also can use this approach to free (PAGE_SIZE - 1) vmemmap pages.
*
* Apart from the HugeTLB page of the pmd/pud level mapping, some architectures
* (e.g. aarch64) provides a contiguous bit in the translation table entries
@@ -166,7 +166,13 @@
*
* The contiguous bit is used to increase the mapping size at the pmd and pte
* (last) level. So this type of HugeTLB page can be optimized only when its
- * size of the struct page structs is greater than 2 pages.
+ * size of the struct page structs is greater than 1 page.
+ *
+ * Notice: The head vmemmap page is not freed to the buddy allocator and all
+ * tail vmemmap pages are mapped to the head vmemmap page frame. So we can see
+ * more than one struct page struct with PG_head (e.g. 8 per 2 MB HugeTLB page)
+ * associated with each HugeTLB page. The compound_head() can handle this
+ * correctly (more details refer to the comment above compound_head()).
*/
#define pr_fmt(fmt) "HugeTLB: " fmt
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-list_lru-transpose-the-array-of-per-node-per-memcg-lru-lists.patch
mm-introduce-kmem_cache_alloc_lru.patch
fs-introduce-alloc_inode_sb-to-allocate-filesystems-specific-inode.patch
fs-allocate-inode-by-using-alloc_inode_sb.patch
f2fs-allocate-inode-by-using-alloc_inode_sb.patch
mm-dcache-use-kmem_cache_alloc_lru-to-allocate-dentry.patch
xarray-use-kmem_cache_alloc_lru-to-allocate-xa_node.patch
mm-memcontrol-move-memcg_online_kmem-to-mem_cgroup_css_online.patch
mm-list_lru-allocate-list_lru_one-only-when-needed.patch
mm-list_lru-rename-memcg_drain_all_list_lrus-to-memcg_reparent_list_lrus.patch
mm-list_lru-replace-linear-array-with-xarray.patch
mm-memcontrol-reuse-memory-cgroup-id-for-kmem-id.patch
mm-memcontrol-fix-cannot-alloc-the-maximum-memcg-id.patch
mm-list_lru-rename-list_lru_per_memcg-to-list_lru_memcg.patch
mm-memcontrol-rename-memcg_cache_id-to-memcg_kmem_id.patch
mm-thp-fix-wrong-cache-flush-in-remove_migration_pmd.patch
mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch
mm-hugetlb-fix-missing-cache-flush-in-copy_huge_page_from_user.patch
mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch
mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte.patch
mm-userfaultfd-fix-missing-cache-flush-in-mcopy_atomic_pte-and-__mcopy_atomic.patch
mm-replace-multiple-dcache-flush-with-flush_dcache_folio.patch
mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page.patch
mm-hugetlb-replace-hugetlb_free_vmemmap_enabled-with-a-static_key.patch
mm-sparsemem-use-page-table-lock-to-protect-kernel-pmd-operations.patch
selftests-vm-add-a-hugetlb-test-case.patch
mm-sparsemem-move-vmemmap-related-to-hugetlb-to-config_hugetlb_page_free_vmemmap.patch
