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SubjectRe: [PATCH 06/18] mm, hugetlb: remove vma_need_reservation()
Date
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> vma_need_reservation() can be substituted by vma_has_reserves()
> with minor change. These function do almost same thing,
> so unifying them is better to maintain.

I found the resulting code confusing and complex. I am sure there is
more that what is explained in the commit message. If you are just doing
this for cleanup, may be we should avoid doing this ?


>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index bf2ee11..ff46a2c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -451,8 +451,18 @@ void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
> vma->vm_private_data = (void *)0;
> }
>
> -/* Returns true if the VMA has associated reserve pages */
> -static int vma_has_reserves(struct vm_area_struct *vma, long chg)
> +/*
> + * Determine if the huge page at addr within the vma has an associated
> + * reservation. Where it does not we will need to logically increase
> + * reservation and actually increase subpool usage before an allocation
> + * can occur. Where any new reservation would be required the
> + * reservation change is prepared, but not committed. Once the page
> + * has been allocated from the subpool and instantiated the change should
> + * be committed via vma_commit_reservation. No action is required on
> + * failure.
> + */
> +static int vma_has_reserves(struct hstate *h,
> + struct vm_area_struct *vma, unsigned long addr)
> {
> if (vma->vm_flags & VM_NORESERVE) {
> /*
> @@ -464,10 +474,22 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
> * step. Currently, we don't have any other solution to deal
> * with this situation properly, so add work-around here.
> */
> - if (vma->vm_flags & VM_MAYSHARE && chg == 0)
> - return 1;
> - else
> - return 0;
> + if (vma->vm_flags & VM_MAYSHARE) {
> + struct address_space *mapping = vma->vm_file->f_mapping;
> + struct inode *inode = mapping->host;
> + pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> + struct resv_map *resv = inode->i_mapping->private_data;
> + long chg;
> +
> + chg = region_chg(resv, idx, idx + 1);
> + if (chg < 0)
> + return -ENOMEM;
> +
> + if (chg == 0)
> + return 1;
> + }
> +
> + return 0;
> }
>
> /* Shared mappings always use reserves */
> @@ -478,8 +500,16 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
> * Only the process that called mmap() has reserves for
> * private mappings.
> */
> - if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
> + if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
> + pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> + struct resv_map *resv = vma_resv_map(vma);
> +
> + /* Just for allocating region structure */
> + if (region_chg(resv, idx, idx + 1) < 0)
> + return -ENOMEM;
> +
> return 1;
> + }
>
> return 0;
> }
> @@ -542,8 +572,7 @@ static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
>
> static struct page *dequeue_huge_page_vma(struct hstate *h,
> struct vm_area_struct *vma,
> - unsigned long address, int avoid_reserve,
> - long chg)
> + unsigned long address, int avoid_reserve)
> {
> struct page *page = NULL;
> struct mempolicy *mpol;
> @@ -558,7 +587,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
> * have no page reserves. This check ensures that reservations are
> * not "stolen". The child may still get SIGKILLed
> */
> - if (!vma_has_reserves(vma, chg) &&
> + if (!vma_has_reserves(h, vma, address) &&
> h->free_huge_pages - h->resv_huge_pages == 0)
> return NULL;
>
> @@ -578,7 +607,7 @@ retry_cpuset:
> if (page) {
> if (avoid_reserve)
> break;
> - if (!vma_has_reserves(vma, chg))
> + if (!vma_has_reserves(h, vma, address))
> break;
>
> h->resv_huge_pages--;
> @@ -1077,42 +1106,6 @@ static void return_unused_surplus_pages(struct hstate *h,
> }
> }
>
> -/*
> - * Determine if the huge page at addr within the vma has an associated
> - * reservation. Where it does not we will need to logically increase
> - * reservation and actually increase subpool usage before an allocation
> - * can occur. Where any new reservation would be required the
> - * reservation change is prepared, but not committed. Once the page
> - * has been allocated from the subpool and instantiated the change should
> - * be committed via vma_commit_reservation. No action is required on
> - * failure.
> - */
> -static long vma_needs_reservation(struct hstate *h,
> - struct vm_area_struct *vma, unsigned long addr)
> -{
> - struct address_space *mapping = vma->vm_file->f_mapping;
> - struct inode *inode = mapping->host;
> -
> - if (vma->vm_flags & VM_MAYSHARE) {
> - pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> - struct resv_map *resv = inode->i_mapping->private_data;
> -
> - return region_chg(resv, idx, idx + 1);
> -
> - } else if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
> - return 1;
> -
> - } else {
> - long err;
> - pgoff_t idx = vma_hugecache_offset(h, vma, addr);
> - struct resv_map *resv = vma_resv_map(vma);
> -
> - err = region_chg(resv, idx, idx + 1);
> - if (err < 0)
> - return err;
> - return 0;
> - }
> -}
> static void vma_commit_reservation(struct hstate *h,
> struct vm_area_struct *vma, unsigned long addr)
> {
> @@ -1140,8 +1133,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
> struct hugepage_subpool *spool = subpool_vma(vma);
> struct hstate *h = hstate_vma(vma);
> struct page *page;
> - long chg;
> - int ret, idx;
> + int ret, idx, has_reserve;
> struct hugetlb_cgroup *h_cg;
>
> idx = hstate_index(h);
> @@ -1153,20 +1145,21 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
> * need pages and subpool limit allocated allocated if no reserve
> * mapping overlaps.
> */
> - chg = vma_needs_reservation(h, vma, addr);
> - if (chg < 0)
> + has_reserve = vma_has_reserves(h, vma, addr);
> + if (has_reserve < 0)
> return ERR_PTR(-ENOMEM);
> - if (chg)
> - if (hugepage_subpool_get_pages(spool, chg))
> +
> + if (!has_reserve && (hugepage_subpool_get_pages(spool, 1) < 0))
> return ERR_PTR(-ENOSPC);
>
> ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
> if (ret) {
> - hugepage_subpool_put_pages(spool, chg);
> + if (!has_reserve)
> + hugepage_subpool_put_pages(spool, 1);
> return ERR_PTR(-ENOSPC);
> }
> spin_lock(&hugetlb_lock);
> - page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg);
> + page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve);
> if (!page) {
> spin_unlock(&hugetlb_lock);
> page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
> @@ -1174,7 +1167,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
> hugetlb_cgroup_uncharge_cgroup(idx,
> pages_per_huge_page(h),
> h_cg);
> - hugepage_subpool_put_pages(spool, chg);
> + if (!has_reserve)
> + hugepage_subpool_put_pages(spool, 1);
> return ERR_PTR(-ENOSPC);
> }
> spin_lock(&hugetlb_lock);
> @@ -2769,7 +2763,7 @@ retry:
> * the spinlock.
> */
> if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
> - if (vma_needs_reservation(h, vma, address) < 0) {
> + if (vma_has_reserves(h, vma, address) < 0) {
> ret = VM_FAULT_OOM;
> goto backout_unlocked;
> }
> @@ -2860,7 +2854,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> * consumed.
> */
> if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
> - if (vma_needs_reservation(h, vma, address) < 0) {
> + if (vma_has_reserves(h, vma, address) < 0) {
> ret = VM_FAULT_OOM;
> goto out_mutex;
> }
> --
> 1.7.9.5



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