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Subject[PATCH v12 3/9] hugetlb_cgroup: add reservation accounting for private mappings
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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.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>

---

Changes in v12:
- Very minor interface update for readability.

Changes in v11:
- Refactored hugetlb_cgroup_uncharge_conuter a bit to eliminate
unnecessary #ifdefs.
- Added resv_map_set_hugetlb_cgroup_uncharge_info() to eliminate #ifdefs
in the middle of hugetlb logic.

Changes in v10:
- Fixed cases where the mapping is private but cgroup accounting is disabled.

Changes in V9:
- Updated for reparenting of hugetlb reservation accounting.

---
include/linux/hugetlb.h | 10 ++++++++
include/linux/hugetlb_cgroup.h | 39 +++++++++++++++++++++++++---
mm/hugetlb.c | 47 +++++++++++++++++++++++++++++++---
mm/hugetlb_cgroup.c | 41 +++++------------------------
4 files changed, 97 insertions(+), 40 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index dea6143aa0685..5491932ea5758 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -46,6 +46,16 @@ 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 either the mapping is shared, or
+ * cgroup accounting is disabled for this resv_map.
+ */
+ struct page_counter *reservation_counter;
+ unsigned long pages_per_hpage;
+ struct cgroup_subsys_state *css;
+#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 5443f4548d523..9974817eb995f 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -27,6 +27,33 @@ struct hugetlb_cgroup;
#define HUGETLB_CGROUP_MIN_ORDER 2

#ifdef CONFIG_CGROUP_HUGETLB
+enum hugetlb_memory_event {
+ HUGETLB_MAX,
+ HUGETLB_NR_MEMORY_EVENTS,
+};
+
+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 rsvd_hugepage[HUGE_MAX_HSTATE];
+
+ atomic_long_t events[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];
+ atomic_long_t events_local[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];
+
+ /* Handle for "hugetlb.events" */
+ struct cgroup_file events_file[HUGE_MAX_HSTATE];
+
+ /* Handle for "hugetlb.events.local" */
+ struct cgroup_file events_local_file[HUGE_MAX_HSTATE];
+};

static inline struct hugetlb_cgroup *
__hugetlb_cgroup_from_page(struct page *page, bool rsvd)
@@ -102,9 +129,9 @@ extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
struct hugetlb_cgroup *h_cg);
extern void hugetlb_cgroup_uncharge_cgroup_rsvd(int idx, unsigned long nr_pages,
struct hugetlb_cgroup *h_cg);
-extern void hugetlb_cgroup_uncharge_counter(struct page_counter *p,
- unsigned long nr_pages,
- struct cgroup_subsys_state *css);
+extern void hugetlb_cgroup_uncharge_counter(struct resv_map *resv,
+ unsigned long start,
+ unsigned long end);

extern void hugetlb_cgroup_file_init(void) __init;
extern void hugetlb_cgroup_migrate(struct page *oldhpage,
@@ -193,6 +220,12 @@ hugetlb_cgroup_uncharge_cgroup_rsvd(int idx, unsigned long nr_pages,
{
}

+static inline void hugetlb_cgroup_uncharge_counter(struct resv_map *resv,
+ unsigned long start,
+ unsigned long end)
+{
+}
+
static inline void hugetlb_cgroup_file_init(void)
{
}
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 357817e33fb34..ac7bab0afafe7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -650,6 +650,25 @@ static void set_vma_private_data(struct vm_area_struct *vma,
vma->vm_private_data = (void *)value;
}

+static void
+resv_map_set_hugetlb_cgroup_uncharge_info(struct resv_map *resv_map,
+ struct hugetlb_cgroup *h_cg,
+ struct hstate *h)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+ if (!h_cg || !h) {
+ resv_map->reservation_counter = NULL;
+ resv_map->pages_per_hpage = 0;
+ resv_map->css = NULL;
+ } else {
+ resv_map->reservation_counter =
+ &h_cg->rsvd_hugepage[hstate_index(h)];
+ resv_map->pages_per_hpage = pages_per_huge_page(h);
+ resv_map->css = &h_cg->css;
+ }
+#endif
+}
+
struct resv_map *resv_map_alloc(void)
{
struct resv_map *resv_map = kmalloc(sizeof(*resv_map), GFP_KERNEL);
@@ -666,6 +685,13 @@ struct resv_map *resv_map_alloc(void)
INIT_LIST_HEAD(&resv_map->regions);

resv_map->adds_in_progress = 0;
+ /*
+ * 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_set_hugetlb_cgroup_uncharge_info(resv_map, NULL, NULL);

INIT_LIST_HEAD(&resv_map->region_cache);
list_add(&rg->link, &resv_map->region_cache);
@@ -3190,9 +3216,7 @@ static void hugetlb_vm_op_close(struct vm_area_struct *vma)
end = vma_hugecache_offset(h, vma, vma->vm_end);

reserve = (end - start) - region_count(resv, start, end);
-
- kref_put(&resv->refs, resv_map_release);
-
+ hugetlb_cgroup_uncharge_counter(resv, start, end);
if (reserve) {
/*
* Decrement reserve counts. The global reserve count may be
@@ -3201,6 +3225,8 @@ 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)
@@ -4547,6 +4573,7 @@ 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 */
@@ -4580,12 +4607,26 @@ int hugetlb_reserve_pages(struct inode *inode,
chg = region_chg(resv_map, from, to);

} else {
+ /* Private mapping. */
resv_map = resv_map_alloc();
if (!resv_map)
return -ENOMEM;

chg = to - from;

+ if (hugetlb_cgroup_charge_cgroup_rsvd(
+ hstate_index(h), chg * pages_per_huge_page(h),
+ &h_cg)) {
+ kref_put(&resv_map->refs, resv_map_release);
+ return -ENOMEM;
+ }
+
+ /*
+ * Since this branch handles private mappings, we attach the
+ * counter to uncharge for this reservation off resv_map.
+ */
+ resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);
+
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 b8246389fb153..bae7bf6b8372f 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -23,34 +23,6 @@
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>

-enum hugetlb_memory_event {
- HUGETLB_MAX,
- HUGETLB_NR_MEMORY_EVENTS,
-};
-
-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 rsvd_hugepage[HUGE_MAX_HSTATE];
-
- atomic_long_t events[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];
- atomic_long_t events_local[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];
-
- /* Handle for "hugetlb.events" */
- struct cgroup_file events_file[HUGE_MAX_HSTATE];
-
- /* Handle for "hugetlb.events.local" */
- struct cgroup_file events_local_file[HUGE_MAX_HSTATE];
-};
-
#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
#define MEMFILE_IDX(val) (((val) >> 16) & 0xffff)
#define MEMFILE_ATTR(val) ((val) & 0xffff)
@@ -408,15 +380,16 @@ void hugetlb_cgroup_uncharge_cgroup_rsvd(int idx, unsigned long nr_pages,
__hugetlb_cgroup_uncharge_cgroup(idx, nr_pages, h_cg, true);
}

-void hugetlb_cgroup_uncharge_counter(struct page_counter *p,
- unsigned long nr_pages,
- struct cgroup_subsys_state *css)
+void hugetlb_cgroup_uncharge_counter(struct resv_map *resv, unsigned long start,
+ unsigned long end)
{
- if (hugetlb_cgroup_disabled() || !p || !css)
+ if (hugetlb_cgroup_disabled() || !resv || !resv->reservation_counter ||
+ !resv->css)
return;

- page_counter_uncharge(p, nr_pages);
- css_put(css);
+ page_counter_uncharge(resv->reservation_counter,
+ (end - start) * resv->pages_per_hpage);
+ css_put(resv->css);
}

enum {
--
2.25.0.225.g125e21ebc7-goog
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