[PATCH v12 5/9] hugetlb_cgroup: add accounting for shared mappings

From: Mina Almasry
Date: Tue Feb 11 2020 - 16:32:20 EST

For shared mappings, the pointer to the hugetlb_cgroup to uncharge lives
in the resv_map entries, in file_region->reservation_counter.

After a call to region_chg, we charge the approprate hugetlb_cgroup, and if
successful, we pass on the hugetlb_cgroup info to a follow up region_add call.
When a file_region entry is added to the resv_map via region_add, we put the
pointer to that cgroup in file_region->reservation_counter. If charging doesn't
succeed, we report the error to the caller, so that the kernel fails the
reservation.

On region_del, which is when the hugetlb memory is unreserved, we also uncharge
the file_region->reservation_counter.

Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>

---

Changes in v12:
- Removed per-file-region pages_per_hpage field.
- Rearranged some function params.
- Fixed goto out_put_pages error condition.

Changes in v11:
- Created new function, hugetlb_cgroup_uncharge_file_region to clean up
some #ifdefs.
- Moved file_region definition to hugetlb.h.
- Added copy_hugetlb_cgroup_uncharge_info function to clean up more
#ifdefs in the middle of hugetlb code.

Changes in v10:
- Deleted duplicated code snippet.

Changes in V9:
- Updated for hugetlb reservation repareting.

---
include/linux/hugetlb.h | 35 ++++++++
include/linux/hugetlb_cgroup.h | 10 +++
mm/hugetlb.c | 148 +++++++++++++++++++++------------
mm/hugetlb_cgroup.c | 15 ++++
4 files changed, 154 insertions(+), 54 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 5491932ea5758..50480d16bd334 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -57,6 +57,41 @@ struct resv_map {
struct cgroup_subsys_state *css;
#endif
};
+
+/*
+ * Region tracking -- allows tracking of reservations and instantiated pages
+ * across the pages in a mapping.
+ *
+ * The region data structures are embedded into a resv_map and protected
+ * by a resv_map's lock. The set of regions within the resv_map represent
+ * reservations for huge pages, or huge pages that have already been
+ * instantiated within the map. The from and to elements are huge page
+ * indicies into the associated mapping. from indicates the starting index
+ * of the region. to represents the first index past the end of the region.
+ *
+ * For example, a file region structure with from == 0 and to == 4 represents
+ * four huge pages in a mapping. It is important to note that the to element
+ * represents the first element past the end of the region. This is used in
+ * arithmetic as 4(to) - 0(from) = 4 huge pages in the region.
+ *
+ * Interval notation of the form [from, to) will be used to indicate that
+ * the endpoint from is inclusive and to is exclusive.
+ */
+struct file_region {
+ struct list_head link;
+ long from;
+ long to;
+#ifdef CONFIG_CGROUP_HUGETLB
+ /*
+ * On shared mappings, each reserved region appears as a struct
+ * file_region in resv_map. These fields hold the info needed to
+ * uncharge each reservation.
+ */
+ struct page_counter *reservation_counter;
+ 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 9974817eb995f..a09d4164ba910 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -133,11 +133,21 @@ extern void hugetlb_cgroup_uncharge_counter(struct resv_map *resv,
unsigned long start,
unsigned long end);

+extern void hugetlb_cgroup_uncharge_file_region(struct resv_map *resv,
+ struct file_region *rg,
+ unsigned long nr_pages);
+
extern void hugetlb_cgroup_file_init(void) __init;
extern void hugetlb_cgroup_migrate(struct page *oldhpage,
struct page *newhpage);

#else
+static inline void hugetlb_cgroup_uncharge_file_region(struct resv_map *resv,
+ struct file_region *rg,
+ unsigned long nr_pages)
+{
+}
+
static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
{
return NULL;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 57739e1aedeca..a9171c3cbed6b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -220,31 +220,6 @@ static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma)
return subpool_inode(file_inode(vma->vm_file));
}

-/*
- * Region tracking -- allows tracking of reservations and instantiated pages
- * across the pages in a mapping.
- *
- * The region data structures are embedded into a resv_map and protected
- * by a resv_map's lock. The set of regions within the resv_map represent
- * reservations for huge pages, or huge pages that have already been
- * instantiated within the map. The from and to elements are huge page
- * indicies into the associated mapping. from indicates the starting index
- * of the region. to represents the first index past the end of the region.
- *
- * For example, a file region structure with from == 0 and to == 4 represents
- * four huge pages in a mapping. It is important to note that the to element
- * represents the first element past the end of the region. This is used in
- * arithmetic as 4(to) - 0(from) = 4 huge pages in the region.
- *
- * Interval notation of the form [from, to) will be used to indicate that
- * the endpoint from is inclusive and to is exclusive.
- */
-struct file_region {
- struct list_head link;
- long from;
- long to;
-};
-
/* Helper that removes a struct file_region from the resv_map cache and returns
* it for use.
*/
@@ -266,6 +241,41 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
return nrg;
}

+static void copy_hugetlb_cgroup_uncharge_info(struct file_region *nrg,
+ struct file_region *rg)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+ nrg->reservation_counter = rg->reservation_counter;
+ nrg->css = rg->css;
+ if (rg->css)
+ css_get(rg->css);
+#endif
+}
+
+/* Helper that records hugetlb_cgroup uncharge info. */
+static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup *h_cg,
+ struct hstate *h,
+ struct resv_map *resv,
+ struct file_region *nrg)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+ if (h_cg) {
+ nrg->reservation_counter =
+ &h_cg->rsvd_hugepage[hstate_index(h)];
+ nrg->css = &h_cg->css;
+ if (!resv->pages_per_hpage)
+ resv->pages_per_hpage = pages_per_huge_page(h);
+ /* pages_per_hpage should be the same for all entries in
+ * a resv_map.
+ */
+ VM_BUG_ON(resv->pages_per_hpage != pages_per_huge_page(h));
+ } else {
+ nrg->reservation_counter = NULL;
+ nrg->css = NULL;
+ }
+#endif
+}
+
/* Must be called with resv->lock held. Calling this with count_only == true
* will count the number of pages to be added but will not modify the linked
* list. If regions_needed != NULL and count_only == true, then regions_needed
@@ -273,7 +283,9 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
* add the regions for this range.
*/
static long add_reservation_in_range(struct resv_map *resv, long f, long t,
- long *regions_needed, bool count_only)
+ struct hugetlb_cgroup *h_cg,
+ struct hstate *h, long *regions_needed,
+ bool count_only)
{
long add = 0;
struct list_head *head = &resv->regions;
@@ -312,6 +324,8 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
if (!count_only) {
nrg = get_file_region_entry_from_cache(
resv, last_accounted_offset, rg->from);
+ record_hugetlb_cgroup_uncharge_info(h_cg, h,
+ resv, nrg);
list_add(&nrg->link, rg->link.prev);
} else if (regions_needed)
*regions_needed += 1;
@@ -328,6 +342,7 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
if (!count_only) {
nrg = get_file_region_entry_from_cache(
resv, last_accounted_offset, t);
+ record_hugetlb_cgroup_uncharge_info(h_cg, h, resv, nrg);
list_add(&nrg->link, rg->link.prev);
} else if (regions_needed)
*regions_needed += 1;
@@ -355,7 +370,8 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
* 1 page will only require at most 1 entry.
*/
static long region_add(struct resv_map *resv, long f, long t,
- long in_regions_needed)
+ long in_regions_needed, struct hstate *h,
+ struct hugetlb_cgroup *h_cg)
{
long add = 0, actual_regions_needed = 0, i = 0;
struct file_region *trg = NULL, *rg = NULL;
@@ -367,7 +383,8 @@ static long region_add(struct resv_map *resv, long f, long t,
retry:

/* Count how many regions are actually needed to execute this add. */
- add_reservation_in_range(resv, f, t, &actual_regions_needed, true);
+ add_reservation_in_range(resv, f, t, NULL, NULL, &actual_regions_needed,
+ true);

/*
* Check for sufficient descriptors in the cache to accommodate
@@ -405,7 +422,7 @@ static long region_add(struct resv_map *resv, long f, long t,
goto retry;
}

- add = add_reservation_in_range(resv, f, t, NULL, false);
+ add = add_reservation_in_range(resv, f, t, h_cg, h, NULL, false);

resv->adds_in_progress -= in_regions_needed;

@@ -453,7 +470,8 @@ static long region_chg(struct resv_map *resv, long f, long t,
spin_lock(&resv->lock);

/* Count how many hugepages in this range are NOT respresented. */
- chg = add_reservation_in_range(resv, f, t, out_regions_needed, true);
+ chg = add_reservation_in_range(resv, f, t, NULL, NULL,
+ out_regions_needed, true);

if (*out_regions_needed == 0)
*out_regions_needed = 1;
@@ -589,11 +607,17 @@ static long region_del(struct resv_map *resv, long f, long t)
/* New entry for end of split region */
nrg->from = t;
nrg->to = rg->to;
+
+ copy_hugetlb_cgroup_uncharge_info(nrg, rg);
+
INIT_LIST_HEAD(&nrg->link);

/* Original entry is trimmed */
rg->to = f;

+ hugetlb_cgroup_uncharge_file_region(
+ resv, rg, nrg->to - nrg->from);
+
list_add(&nrg->link, &rg->link);
nrg = NULL;
break;
@@ -601,6 +625,8 @@ static long region_del(struct resv_map *resv, long f, long t)

if (f <= rg->from && t >= rg->to) { /* Remove entire region */
del += rg->to - rg->from;
+ hugetlb_cgroup_uncharge_file_region(resv, rg,
+ rg->to - rg->from);
list_del(&rg->link);
kfree(rg);
continue;
@@ -609,9 +635,15 @@ static long region_del(struct resv_map *resv, long f, long t)
if (f <= rg->from) { /* Trim beginning of region */
del += t - rg->from;
rg->from = t;
+
+ hugetlb_cgroup_uncharge_file_region(resv, rg,
+ t - rg->from);
} else { /* Trim end of region */
del += rg->to - f;
rg->to = f;
+
+ hugetlb_cgroup_uncharge_file_region(resv, rg,
+ rg->to - f);
}
}

@@ -2018,7 +2050,7 @@ static long __vma_reservation_common(struct hstate *h,
VM_BUG_ON(dummy_out_regions_needed != 1);
break;
case VMA_COMMIT_RESV:
- ret = region_add(resv, idx, idx + 1, 1);
+ ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
/* region_add calls of range 1 should never fail. */
VM_BUG_ON(ret < 0);
break;
@@ -2028,7 +2060,7 @@ static long __vma_reservation_common(struct hstate *h,
break;
case VMA_ADD_RESV:
if (vma->vm_flags & VM_MAYSHARE) {
- ret = region_add(resv, idx, idx + 1, 1);
+ ret = region_add(resv, idx, idx + 1, 1, NULL, NULL);
/* region_add calls of range 1 should never fail. */
VM_BUG_ON(ret < 0);
} else {
@@ -4686,7 +4718,7 @@ 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;
+ struct hugetlb_cgroup *h_cg = NULL;
long gbl_reserve, regions_needed = 0;

/* This should never happen */
@@ -4727,19 +4759,6 @@ int hugetlb_reserve_pages(struct inode *inode,

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);
}
@@ -4749,6 +4768,21 @@ int hugetlb_reserve_pages(struct inode *inode,
goto out_err;
}

+ ret = hugetlb_cgroup_charge_cgroup_rsvd(
+ hstate_index(h), chg * pages_per_huge_page(h), &h_cg);
+
+ if (ret < 0) {
+ ret = -ENOMEM;
+ goto out_err;
+ }
+
+ if (vma && !(vma->vm_flags & VM_MAYSHARE) && h_cg) {
+ /* For private mappings, the hugetlb_cgroup uncharge info hangs
+ * of the resv_map.
+ */
+ resv_map_set_hugetlb_cgroup_uncharge_info(resv_map, h_cg, h);
+ }
+
/*
* There must be enough pages in the subpool for the mapping. If
* the subpool has a minimum size, there may be some global
@@ -4757,7 +4791,7 @@ int hugetlb_reserve_pages(struct inode *inode,
gbl_reserve = hugepage_subpool_get_pages(spool, chg);
if (gbl_reserve < 0) {
ret = -ENOSPC;
- goto out_err;
+ goto out_uncharge_cgroup;
}

/*
@@ -4766,9 +4800,7 @@ int hugetlb_reserve_pages(struct inode *inode,
*/
ret = hugetlb_acct_memory(h, gbl_reserve);
if (ret < 0) {
- /* put back original number of pages, chg */
- (void)hugepage_subpool_put_pages(spool, chg);
- goto out_err;
+ goto out_put_pages;
}

/*
@@ -4783,13 +4815,11 @@ int hugetlb_reserve_pages(struct inode *inode,
* else has to be done for private mappings here
*/
if (!vma || vma->vm_flags & VM_MAYSHARE) {
- add = region_add(resv_map, from, to, regions_needed);
+ add = region_add(resv_map, from, to, regions_needed, h, h_cg);

if (unlikely(add < 0)) {
hugetlb_acct_memory(h, -gbl_reserve);
- /* put back original number of pages, chg */
- (void)hugepage_subpool_put_pages(spool, chg);
- goto out_err;
+ goto out_put_pages;
} else if (unlikely(chg > add)) {
/*
* pages in this range were added to the reserve
@@ -4800,12 +4830,22 @@ int hugetlb_reserve_pages(struct inode *inode,
*/
long rsv_adjust;

+ hugetlb_cgroup_uncharge_cgroup_rsvd(
+ hstate_index(h),
+ (chg - add) * pages_per_huge_page(h), h_cg);
+
rsv_adjust = hugepage_subpool_put_pages(spool,
chg - add);
hugetlb_acct_memory(h, -rsv_adjust);
}
}
return 0;
+out_put_pages:
+ /* put back original number of pages, chg */
+ (void)hugepage_subpool_put_pages(spool, chg);
+out_uncharge_cgroup:
+ hugetlb_cgroup_uncharge_cgroup_rsvd(hstate_index(h),
+ chg * pages_per_huge_page(h), h_cg);
out_err:
if (!vma || vma->vm_flags & VM_MAYSHARE)
/* Only call region_abort if the region_chg succeeded but the
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index bae7bf6b8372f..ad777fecad28a 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -392,6 +392,21 @@ void hugetlb_cgroup_uncharge_counter(struct resv_map *resv, unsigned long start,
css_put(resv->css);
}

+void hugetlb_cgroup_uncharge_file_region(struct resv_map *resv,
+ struct file_region *rg,
+ unsigned long nr_pages)
+{
+ if (hugetlb_cgroup_disabled() || !resv || !rg || !nr_pages)
+ return;
+
+ if (rg->reservation_counter && resv->pages_per_hpage && nr_pages > 0 &&
+ !resv->reservation_counter) {
+ page_counter_uncharge(rg->reservation_counter,
+ nr_pages * resv->pages_per_hpage);
+ css_put(rg->css);
+ }
+}
+
enum {
RES_USAGE,
RES_RSVD_USAGE,
--
2.25.0.225.g125e21ebc7-goog