Normally the pointer to the cgroup to uncharge hangs off the struct page, and gets queried when it's time to free the page. With hugetlb_cgroup reservations, this is not possible. Because it's possible for a page to be reserved by one task and actually faulted in by another task.
The best place to put the hugetlb_cgroup pointer to uncharge for reservations is in the resv_map. But, because the resv_map has different semantics for private and shared mappings, the code patch to charge/uncharge shared and private mappings is different. This patch implements charging and uncharging for private mappings.
For private mappings, the counter to uncharge is in resv_map->reservation_counter. On initializing the resv_map this is set to NULL. On reservation of a region in private mapping, the tasks hugetlb_cgroup is charged and the hugetlb_cgroup is placed is resv_map->reservation_counter.
On hugetlb_vm_op_close, we uncharge resv_map->reservation_counter.
--- include/linux/hugetlb.h | 8 ++++++ include/linux/hugetlb_cgroup.h | 11 ++++++++ mm/hugetlb.c | 47 ++++++++++++++++++++++++++++++++-- mm/hugetlb_cgroup.c | 12 --------- 4 files changed, 64 insertions(+), 14 deletions(-)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 6777b3013345d..90b3c928d16c1 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -46,6 +46,14 @@ struct resv_map { long adds_in_progress; struct list_head region_cache; long region_cache_count; + #ifdef CONFIG_CGROUP_HUGETLB + /* + * On private mappings, the counter to uncharge reservations is stored + * here. If these fields are 0, then the mapping is shared. + */ + struct page_counter *reservation_counter; + unsigned long pages_per_hpage; +#endif }; extern struct resv_map *resv_map_alloc(void); void resv_map_release(struct kref *ref); diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h index 0725f809cd2d9..1fdde63a4e775 100644 --- a/include/linux/hugetlb_cgroup.h +++ b/include/linux/hugetlb_cgroup.h @@ -25,6 +25,17 @@ struct hugetlb_cgroup; #define HUGETLB_CGROUP_MIN_ORDER 2
#ifdef CONFIG_CGROUP_HUGETLB +struct hugetlb_cgroup { + struct cgroup_subsys_state css; + /* + * the counter to account for hugepages from hugetlb. + */ + struct page_counter hugepage[HUGE_MAX_HSTATE]; + /* + * the counter to account for hugepage reservations from hugetlb. + */ + struct page_counter reserved_hugepage[HUGE_MAX_HSTATE]; +};
static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page) { diff --git a/mm/hugetlb.c b/mm/hugetlb.c index c153bef42e729..235996aef6618 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -711,6 +711,16 @@ struct resv_map *resv_map_alloc(void) INIT_LIST_HEAD(&resv_map->regions);
resv_map->adds_in_progress = 0; +#ifdef CONFIG_CGROUP_HUGETLB + /* + * Initialize these to 0. On shared mappings, 0's here indicate these + * fields don't do cgroup accounting. On private mappings, these will be + * re-initialized to the proper values, to indicate that hugetlb cgroup + * reservations are to be un-charged from here. + */ + resv_map->reservation_counter = NULL; + resv_map->pages_per_hpage = 0; +#endif
INIT_LIST_HEAD(&resv_map->region_cache); list_add(&rg->link, &resv_map->region_cache); @@ -3192,7 +3202,19 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
reserve = (end - start) - region_count(resv, start, end);
- kref_put(&resv->refs, resv_map_release); +#ifdef CONFIG_CGROUP_HUGETLB + /* + * Since we check for HPAGE_RESV_OWNER above, this must a private + * mapping, and these values should be none-zero, and should point to + * the hugetlb_cgroup counter to uncharge for this reservation. + */ + WARN_ON(!resv->reservation_counter); + WARN_ON(!resv->pages_per_hpage); + + hugetlb_cgroup_uncharge_counter( + resv->reservation_counter, + (end - start) * resv->pages_per_hpage); +#endif
if (reserve) { /* @@ -3202,6 +3224,8 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma) gbl_reserve = hugepage_subpool_put_pages(spool, reserve); hugetlb_acct_memory(h, -gbl_reserve); } + + kref_put(&resv->refs, resv_map_release); }
static int hugetlb_vm_op_split(struct vm_area_struct *vma, unsigned long addr) @@ -4516,6 +4540,7 @@ int hugetlb_reserve_pages(struct inode *inode, struct hstate *h = hstate_inode(inode); struct hugepage_subpool *spool = subpool_inode(inode); struct resv_map *resv_map; + struct hugetlb_cgroup *h_cg; long gbl_reserve;
/* This should never happen */ @@ -4549,11 +4574,29 @@ int hugetlb_reserve_pages(struct inode *inode, chg = region_chg(resv_map, from, to);
} else { + /* Private mapping. */ + chg = to - from; + + if (hugetlb_cgroup_charge_cgroup( + hstate_index(h), + chg * pages_per_huge_page(h), + &h_cg, true)) { + return -ENOMEM; + } + resv_map = resv_map_alloc(); if (!resv_map) return -ENOMEM;
- chg = to - from; +#ifdef CONFIG_CGROUP_HUGETLB + /* + * Since this branch handles private mappings, we attach the + * counter to uncharge for this reservation off resv_map. + */ + resv_map->reservation_counter = + &h_cg->reserved_hugepage[hstate_index(h)]; + resv_map->pages_per_hpage = pages_per_huge_page(h); +#endif
set_vma_resv_map(vma, resv_map); set_vma_resv_flags(vma, HPAGE_RESV_OWNER); diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index 119176a0b2ec5..06e99ae1fec81 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -19,18 +19,6 @@ #include <linux/hugetlb.h> #include <linux/hugetlb_cgroup.h>
-struct hugetlb_cgroup { - struct cgroup_subsys_state css; - /* - * the counter to account for hugepages from hugetlb. - */ - struct page_counter hugepage[HUGE_MAX_HSTATE]; - /* - * the counter to account for hugepage reservations from hugetlb. - */ - struct page_counter reserved_hugepage[HUGE_MAX_HSTATE]; -}; - #define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val)) #define MEMFILE_IDX(val) (((val) >> 16) & 0xffff) #define MEMFILE_ATTR(val) ((val) & 0xffff) -- 2.23.0.rc1.153.gdeed80330f-goog