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Date: Wed, 26 May 2021 19:49:08 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Linux-MM <linux-mm@...ck.org>,
open list <linux-kernel@...r.kernel.org>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Peter Xu <peterx@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] hugetlb: rename HPageRestoreReserve flag to HPageRestoreRsvCnt
On Tue, May 25, 2021 at 4:31 PM Mike Kravetz <mike.kravetz@...cle.com> wrote:
>
> The hugetlb page specific flag HPageRestoreReserve is used to indicate
> that a reservation was consumed and should be restored on error. More
> specifically, this is related to the global reservation count.
>
> It is also possible to have a hugetlb page allocated where the global
> count is not modified, but the reservation map is modified. In such
> cases, the reserve map needs modification in error paths. Code
> performing such modifications will be introduced in a subsequent patch.
>
> Rename the flag HPageRestoreReserve to HPageRestoreRsvCnt so that it
> is more clearly allociated with the global reservation count. No
> functional changes in this patch, just renaming.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> ---
> fs/hugetlbfs/inode.c | 2 +-
> include/linux/hugetlb.h | 6 +++---
> mm/hugetlb.c | 32 ++++++++++++++++----------------
> mm/userfaultfd.c | 14 +++++++-------
> 4 files changed, 27 insertions(+), 27 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 55efd3dd04f6..bb4de5dcd652 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -529,7 +529,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> * the subpool and global reserve usage count can need
> * to be adjusted.
> */
> - VM_BUG_ON(HPageRestoreReserve(page));
> + VM_BUG_ON(HPageRestoreRsvCnt(page));
> remove_huge_page(page);
> freed++;
> if (!truncate_op) {
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 03ca83db0a3e..e5e363fa5d02 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -511,7 +511,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> * of the hugetlb head page. Functions created via the below macros should be
> * used to manipulate these flags.
> *
> - * HPG_restore_reserve - Set when a hugetlb page consumes a reservation at
> + * HPG_restore_rsv_cnt - Set when a hugetlb page consumes a reservation at
> * allocation time. Cleared when page is fully instantiated. Free
> * routine checks flag to restore a reservation on error paths.
> * Synchronization: Examined or modified by code that knows it has
> @@ -535,7 +535,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> * HPG_vmemmap_optimized - Set when the vmemmap pages of the page are freed.
> */
> enum hugetlb_page_flags {
> - HPG_restore_reserve = 0,
> + HPG_restore_rsv_cnt = 0,
> HPG_migratable,
> HPG_temporary,
> HPG_freed,
> @@ -581,7 +581,7 @@ static inline void ClearHPage##uname(struct page *page) \
> /*
> * Create functions associated with hugetlb page flags
> */
> -HPAGEFLAG(RestoreReserve, restore_reserve)
> +HPAGEFLAG(RestoreRsvCnt, restore_rsv_cnt)
> HPAGEFLAG(Migratable, migratable)
> HPAGEFLAG(Temporary, temporary)
> HPAGEFLAG(Freed, freed)
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index c3b2a8a494d6..2a8cea253388 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1165,7 +1165,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> nid = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
> page = dequeue_huge_page_nodemask(h, gfp_mask, nid, nodemask);
> if (page && !avoid_reserve && vma_has_reserves(vma, chg)) {
> - SetHPageRestoreReserve(page);
> + SetHPageRestoreRsvCnt(page);
> h->resv_huge_pages--;
> }
>
> @@ -1549,11 +1549,11 @@ void free_huge_page(struct page *page)
>
> hugetlb_set_page_subpool(page, NULL);
> page->mapping = NULL;
> - restore_reserve = HPageRestoreReserve(page);
> - ClearHPageRestoreReserve(page);
> + restore_reserve = HPageRestoreRsvCnt(page);
> + ClearHPageRestoreRsvCnt(page);
>
> /*
> - * If HPageRestoreReserve was set on page, page allocation consumed a
> + * If HPageRestoreRsvCnt was set on page, page allocation consumed a
> * reservation. If the page was associated with a subpool, there
> * would have been a page reserved in the subpool before allocation
> * via hugepage_subpool_get_pages(). Since we are 'restoring' the
> @@ -2364,9 +2364,9 @@ static long vma_add_reservation(struct hstate *h,
> * specific error paths, a huge page was allocated (via alloc_huge_page)
> * and is about to be freed. If a reservation for the page existed,
> * alloc_huge_page would have consumed the reservation and set
> - * HPageRestoreReserve in the newly allocated page. When the page is freed
> + * HPageRestoreRsvCnt in the newly allocated page. When the page is freed
> * via free_huge_page, the global reservation count will be incremented if
> - * HPageRestoreReserve is set. However, free_huge_page can not adjust the
> + * HPageRestoreRsvCnt is set. However, free_huge_page can not adjust the
> * reserve map. Adjust the reserve map here to be consistent with global
> * reserve count adjustments to be made by free_huge_page.
> */
> @@ -2374,13 +2374,13 @@ static void restore_reserve_on_error(struct hstate *h,
> struct vm_area_struct *vma, unsigned long address,
> struct page *page)
> {
> - if (unlikely(HPageRestoreReserve(page))) {
> + if (unlikely(HPageRestoreRsvCnt(page))) {
> long rc = vma_needs_reservation(h, vma, address);
>
> if (unlikely(rc < 0)) {
> /*
> * Rare out of memory condition in reserve map
> - * manipulation. Clear HPageRestoreReserve so that
> + * manipulation. Clear HPageRestoreRsvCnt so that
> * global reserve count will not be incremented
> * by free_huge_page. This will make it appear
> * as though the reservation for this page was
> @@ -2389,7 +2389,7 @@ static void restore_reserve_on_error(struct hstate *h,
> * is better than inconsistent global huge page
> * accounting of reserve counts.
> */
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
> } else if (rc) {
> rc = vma_add_reservation(h, vma, address);
> if (unlikely(rc < 0))
> @@ -2397,7 +2397,7 @@ static void restore_reserve_on_error(struct hstate *h,
> * See above comment about rare out of
> * memory condition.
> */
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
> } else
> vma_end_reservation(h, vma, address);
> }
> @@ -2602,7 +2602,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> if (!page)
> goto out_uncharge_cgroup;
> if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
> - SetHPageRestoreReserve(page);
> + SetHPageRestoreRsvCnt(page);
> h->resv_huge_pages--;
> }
> spin_lock_irq(&hugetlb_lock);
> @@ -4052,7 +4052,7 @@ hugetlb_install_page(struct vm_area_struct *vma, pte_t *ptep, unsigned long addr
> set_huge_pte_at(vma->vm_mm, addr, ptep, make_huge_pte(vma, new_page, 1));
> hugepage_add_new_anon_rmap(new_page, vma, addr);
> hugetlb_count_add(pages_per_huge_page(hstate_vma(vma)), vma->vm_mm);
> - ClearHPageRestoreReserve(new_page);
> + ClearHPageRestoreRsvCnt(new_page);
> SetHPageMigratable(new_page);
> }
>
> @@ -4525,7 +4525,7 @@ static vm_fault_t hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> spin_lock(ptl);
> ptep = huge_pte_offset(mm, haddr, huge_page_size(h));
> if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
> - ClearHPageRestoreReserve(new_page);
> + ClearHPageRestoreRsvCnt(new_page);
>
> /* Break COW */
> huge_ptep_clear_flush(vma, haddr, ptep);
> @@ -4592,7 +4592,7 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
>
> if (err)
> return err;
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
>
> /*
> * set page dirty so that it will not be removed from cache/file
> @@ -4775,7 +4775,7 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
> goto backout;
>
> if (anon_rmap) {
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
> hugepage_add_new_anon_rmap(page, vma, haddr);
> } else
> page_dup_rmap(page, true);
> @@ -5096,7 +5096,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
> if (vm_shared) {
> page_dup_rmap(page, true);
> } else {
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
> hugepage_add_new_anon_rmap(page, dst_vma, dst_addr);
> }
>
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index 9ce5a3793ad4..58c706697b17 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -432,27 +432,27 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
> * If a reservation for the page existed in the reservation
> * map of a private mapping, the map was modified to indicate
> * the reservation was consumed when the page was allocated.
> - * We clear the HPageRestoreReserve flag now so that the global
> + * We clear the HPageRestoreRsvCnt flag now so that the global
> * reserve count will not be incremented in free_huge_page.
> * The reservation map will still indicate the reservation
> * was consumed and possibly prevent later page allocation.
> * This is better than leaking a global reservation. If no
> * reservation existed, it is still safe to clear
> - * HPageRestoreReserve as no adjustments to reservation counts
> + * HPageRestoreRsvCnt as no adjustments to reservation counts
> * were made during allocation.
> *
> * The reservation map for shared mappings indicates which
> * pages have reservations. When a huge page is allocated
> * for an address with a reservation, no change is made to
> - * the reserve map. In this case HPageRestoreReserve will be
> + * the reserve map. In this case HPageRestoreRsvCnt will be
> * set to indicate that the global reservation count should be
> * incremented when the page is freed. This is the desired
> * behavior. However, when a huge page is allocated for an
> * address without a reservation a reservation entry is added
> - * to the reservation map, and HPageRestoreReserve will not be
> + * to the reservation map, and HPageRestoreRsvCnt will not be
> * set. When the page is freed, the global reserve count will
> * NOT be incremented and it will appear as though we have
> - * leaked reserved page. In this case, set HPageRestoreReserve
> + * leaked reserved page. In this case, set HPageRestoreRsvCnt
> * so that the global reserve count will be incremented to
> * match the reservation map entry which was created.
> *
> @@ -461,9 +461,9 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
> * be different or NULL on error.
> */
> if (vm_alloc_shared)
> - SetHPageRestoreReserve(page);
> + SetHPageRestoreRsvCnt(page);
> else
> - ClearHPageRestoreReserve(page);
> + ClearHPageRestoreRsvCnt(page);
> put_page(page);
> }
> BUG_ON(copied < 0);
> --
> 2.31.1
>
Reviewed-by: Mina Almasry <almasrymina@...gle.com>
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