[PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mina Almasry]

Problem:
Currently tasks attempting to allocate more hugetlb memory than is available get
a failure at mmap/shmget time. This is thanks to Hugetlbfs Reservations [1].
However, if a task attempts to allocate hugetlb memory only more than its
hugetlb_cgroup limit allows, the kernel will allow the mmap/shmget call,
but will SIGBUS the task when it attempts to fault the memory in.

We have developers interested in using hugetlb_cgroups, and they have expressed
dissatisfaction regarding this behavior. We'd like to improve this
behavior such that tasks violating the hugetlb_cgroup limits get an error on
mmap/shmget time, rather than getting SIGBUS'd when they try to fault
the excess memory in.

The underlying problem is that today's hugetlb_cgroup accounting happens
at hugetlb memory *fault* time, rather than at *reservation* time.
Thus, enforcing the hugetlb_cgroup limit only happens at fault time, and
the offending task gets SIGBUS'd.

Proposed Solution:
A new page counter named hugetlb.xMB.reservation_[limit|usage]_in_bytes. This
counter has slightly different semantics than
hugetlb.xMB.[limit|usage]_in_bytes:

- While usage_in_bytes tracks all *faulted* hugetlb memory,
reservation_usage_in_bytes tracks all *reserved* hugetlb memory.

- If a task attempts to reserve more memory than limit_in_bytes allows,
the kernel will allow it to do so. But if a task attempts to reserve
more memory than reservation_limit_in_bytes, the kernel will fail this
reservation.

This proposal is implemented in this patch, with tests to verify
functionality and show the usage.

Alternatives considered:
1. A new cgroup, instead of only a new page_counter attached to
   the existing hugetlb_cgroup. Adding a new cgroup seemed like a lot of code
   duplication with hugetlb_cgroup. Keeping hugetlb related page counters under
   hugetlb_cgroup seemed cleaner as well.

2. Instead of adding a new counter, we considered adding a sysctl that modifies
   the behavior of hugetlb.xMB.[limit|usage]_in_bytes, to do accounting at
   reservation time rather than fault time. Adding a new page_counter seems
   better as userspace could, if it wants, choose to enforce different cgroups
   differently: one via limit_in_bytes, and another via
   reservation_limit_in_bytes. This could be very useful if you're
   transitioning how hugetlb memory is partitioned on your system one
   cgroup at a time, for example. Also, someone may find usage for both
   limit_in_bytes and reservation_limit_in_bytes concurrently, and this
   approach gives them the option to do so.

Caveats:
1. This support is implemented for cgroups-v1. I have not tried
   hugetlb_cgroups with cgroups v2, and AFAICT it's not supported yet.
   This is largely because we use cgroups-v1 for now. If required, I
   can add hugetlb_cgroup support to cgroups v2 in this patch or
   a follow up.
2. Most complicated bit of this patch I believe is: where to store the
   pointer to the hugetlb_cgroup to uncharge at unreservation time?
   Normally the cgroup pointers hang off the struct page. But, with
   hugetlb_cgroup reservations, one task can reserve a specific page and another
   task may fault it in (I believe), so storing the pointer in struct
   page is not appropriate. Proposed approach here is to store the pointer in
   the resv_map. See patch for details.

Signed-off-by: Mina Almasry <almasrymina@google.com>

[1]: https://www.kernel.org/doc/html/latest/vm/hugetlbfs_reserv.html

Changes in v3:
- Addressed comments of Hillf Danton:
  - Added docs.
  - cgroup_files now uses enum.
  - Various readability improvements.
- Addressed comments of Mike Kravetz.
  - region_* functions no longer coalesce file_region entries in the resv_map.
  - region_add() and region_chg() refactored to make them much easier to
    understand and remove duplicated code so this patch doesn't add too much
    complexity.
  - Refactored common functionality into helpers.

Changes in v2:
- Split the patch into a 5 patch series.
- Fixed patch subject.

Mina Almasry (6):
  hugetlb_cgroup: Add hugetlb_cgroup reservation counter
  hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations
  hugetlb_cgroup: add reservation accounting for private mappings
  hugetlb_cgroup: add accounting for shared mappings
  hugetlb_cgroup: Add hugetlb_cgroup reservation tests
  hugetlb_cgroup: Add hugetlb_cgroup reservation docs

 .../admin-guide/cgroup-v1/hugetlb.rst         |  84 ++-
 include/linux/hugetlb.h                       |  24 +-
 include/linux/hugetlb_cgroup.h                |  19 +-
 mm/hugetlb.c                                  | 493 ++++++++++++------
 mm/hugetlb_cgroup.c                           | 187 +++++--
 tools/testing/selftests/vm/.gitignore         |   1 +
 tools/testing/selftests/vm/Makefile           |   4 +
 .../selftests/vm/charge_reserved_hugetlb.sh   | 438 ++++++++++++++++
 .../selftests/vm/write_hugetlb_memory.sh      |  22 +
 .../testing/selftests/vm/write_to_hugetlbfs.c | 252 +++++++++
 10 files changed, 1300 insertions(+), 224 deletions(-)
 create mode 100755 tools/testing/selftests/vm/charge_reserved_hugetlb.sh
 create mode 100644 tools/testing/selftests/vm/write_hugetlb_memory.sh
 create mode 100644 tools/testing/selftests/vm/write_to_hugetlbfs.c

--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 1/6] hugetlb_cgroup: Add hugetlb_cgroup reservation counter

[Mina Almasry]

These counters will track hugetlb reservations rather than hugetlb
memory faulted in. This patch only adds the counter, following patches
add the charging and uncharging of the counter.

---
 include/linux/hugetlb.h |  16 +++++-
 mm/hugetlb_cgroup.c     | 111 ++++++++++++++++++++++++++++++----------
 2 files changed, 100 insertions(+), 27 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index edfca42783192..128ff1aff1c93 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -320,6 +320,20 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,

 #ifdef CONFIG_HUGETLB_PAGE

+enum {
+	HUGETLB_RES_USAGE,
+	HUGETLB_RES_RESERVATION_USAGE,
+	HUGETLB_RES_LIMIT,
+	HUGETLB_RES_RESERVATION_LIMIT,
+	HUGETLB_RES_MAX_USAGE,
+	HUGETLB_RES_RESERVATION_MAX_USAGE,
+	HUGETLB_RES_FAILCNT,
+	HUGETLB_RES_RESERVATION_FAILCNT,
+	HUGETLB_RES_NULL,
+	HUGETLB_RES_MAX,
+};
+
+
 #define HSTATE_NAME_LEN 32
 /* Defines one hugetlb page size */
 struct hstate {
@@ -340,7 +354,7 @@ struct hstate {
 	unsigned int surplus_huge_pages_node[MAX_NUMNODES];
 #ifdef CONFIG_CGROUP_HUGETLB
 	/* cgroup control files */
-	struct cftype cgroup_files[5];
+	struct cftype cgroup_files[HUGETLB_RES_MAX];
 #endif
 	char name[HSTATE_NAME_LEN];
 };
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 68c2f2f3c05b7..51a72624bd1ff 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -25,6 +25,10 @@ struct hugetlb_cgroup {
 	 * 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))
@@ -33,6 +37,15 @@ struct hugetlb_cgroup {

 static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

+static inline
+struct page_counter *hugetlb_cgroup_get_counter(struct hugetlb_cgroup *h_cg, int idx,
+				 bool reserved)
+{
+	if (reserved)
+		return  &h_cg->reserved_hugepage[idx];
+	return &h_cg->hugepage[idx];
+}
+
 static inline
 struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
 {
@@ -254,30 +267,33 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
 	return;
 }

-enum {
-	RES_USAGE,
-	RES_LIMIT,
-	RES_MAX_USAGE,
-	RES_FAILCNT,
-};
-
 static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
 				   struct cftype *cft)
 {
 	struct page_counter *counter;
+	struct page_counter *reserved_counter;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);

 	counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];
+	reserved_counter = &h_cg->reserved_hugepage[MEMFILE_IDX(cft->private)];

 	switch (MEMFILE_ATTR(cft->private)) {
-	case RES_USAGE:
+	case HUGETLB_RES_USAGE:
 		return (u64)page_counter_read(counter) * PAGE_SIZE;
-	case RES_LIMIT:
+	case HUGETLB_RES_RESERVATION_USAGE:
+		return (u64)page_counter_read(reserved_counter) * PAGE_SIZE;
+	case HUGETLB_RES_LIMIT:
 		return (u64)counter->max * PAGE_SIZE;
-	case RES_MAX_USAGE:
+	case HUGETLB_RES_RESERVATION_LIMIT:
+		return (u64)reserved_counter->max * PAGE_SIZE;
+	case HUGETLB_RES_MAX_USAGE:
 		return (u64)counter->watermark * PAGE_SIZE;
-	case RES_FAILCNT:
+	case HUGETLB_RES_RESERVATION_MAX_USAGE:
+		return (u64)reserved_counter->watermark * PAGE_SIZE;
+	case HUGETLB_RES_FAILCNT:
 		return counter->failcnt;
+	case HUGETLB_RES_RESERVATION_FAILCNT:
+		return reserved_counter->failcnt;
 	default:
 		BUG();
 	}
@@ -291,6 +307,7 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
 	int ret, idx;
 	unsigned long nr_pages;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
+	bool reserved = false;

 	if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
 		return -EINVAL;
@@ -304,9 +321,13 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
 	nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));

 	switch (MEMFILE_ATTR(of_cft(of)->private)) {
-	case RES_LIMIT:
+	case HUGETLB_RES_RESERVATION_LIMIT:
+		reserved = true;
+		/* Fall through. */
+	case HUGETLB_RES_LIMIT:
 		mutex_lock(&hugetlb_limit_mutex);
-		ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages);
+		ret = page_counter_set_max(hugetlb_cgroup_get_counter(h_cg, idx, reserved),
+					   nr_pages);
 		mutex_unlock(&hugetlb_limit_mutex);
 		break;
 	default:
@@ -320,18 +341,26 @@ static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
 				    char *buf, size_t nbytes, loff_t off)
 {
 	int ret = 0;
-	struct page_counter *counter;
+	struct page_counter *counter, *reserved_counter;
 	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

 	counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];
+	reserved_counter = &h_cg->reserved_hugepage[
+		MEMFILE_IDX(of_cft(of)->private)];

 	switch (MEMFILE_ATTR(of_cft(of)->private)) {
-	case RES_MAX_USAGE:
+	case HUGETLB_RES_MAX_USAGE:
 		page_counter_reset_watermark(counter);
 		break;
-	case RES_FAILCNT:
+	case HUGETLB_RES_RESERVATION_MAX_USAGE:
+		page_counter_reset_watermark(reserved_counter);
+		break;
+	case HUGETLB_RES_FAILCNT:
 		counter->failcnt = 0;
 		break;
+	case HUGETLB_RES_RESERVATION_FAILCNT:
+		reserved_counter->failcnt = 0;
+		break;
 	default:
 		ret = -EINVAL;
 		break;
@@ -357,37 +386,67 @@ static void __init __hugetlb_cgroup_file_init(int idx)
 	struct hstate *h = &hstates[idx];

 	/* format the size */
-	mem_fmt(buf, 32, huge_page_size(h));
+	mem_fmt(buf, sizeof(buf), huge_page_size(h));

 	/* Add the limit file */
-	cft = &h->cgroup_files[0];
+	cft = &h->cgroup_files[HUGETLB_RES_LIMIT];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
-	cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_LIMIT);
+	cft->read_u64 = hugetlb_cgroup_read_u64;
+	cft->write = hugetlb_cgroup_write;
+
+	/* Add the reservation limit file */
+	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_LIMIT];
+	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_limit_in_bytes",
+		 buf);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_LIMIT);
 	cft->read_u64 = hugetlb_cgroup_read_u64;
 	cft->write = hugetlb_cgroup_write;

 	/* Add the usage file */
-	cft = &h->cgroup_files[1];
+	cft = &h->cgroup_files[HUGETLB_RES_USAGE];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
-	cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_USAGE);
+	cft->read_u64 = hugetlb_cgroup_read_u64;
+
+	/* Add the reservation usage file */
+	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_USAGE];
+	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_usage_in_bytes",
+			buf);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_USAGE);
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* Add the MAX usage file */
-	cft = &h->cgroup_files[2];
+	cft = &h->cgroup_files[HUGETLB_RES_MAX_USAGE];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
-	cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_MAX_USAGE);
+	cft->write = hugetlb_cgroup_reset;
+	cft->read_u64 = hugetlb_cgroup_read_u64;
+
+	/* Add the MAX reservation usage file */
+	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_MAX_USAGE];
+	snprintf(cft->name, MAX_CFTYPE_NAME,
+			"%s.reservation_max_usage_in_bytes", buf);
+	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_MAX_USAGE);
 	cft->write = hugetlb_cgroup_reset;
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* Add the failcntfile */
-	cft = &h->cgroup_files[3];
+	cft = &h->cgroup_files[HUGETLB_RES_FAILCNT];
 	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
-	cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
+	cft->private  = MEMFILE_PRIVATE(idx, HUGETLB_RES_FAILCNT);
+	cft->write = hugetlb_cgroup_reset;
+	cft->read_u64 = hugetlb_cgroup_read_u64;
+
+	/* Add the reservation failcntfile */
+	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_FAILCNT];
+	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_failcnt", buf);
+	cft->private  = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_FAILCNT);
 	cft->write = hugetlb_cgroup_reset;
 	cft->read_u64 = hugetlb_cgroup_read_u64;

 	/* NULL terminate the last cft */
-	cft = &h->cgroup_files[4];
+	cft = &h->cgroup_files[HUGETLB_RES_NULL];
 	memset(cft, 0, sizeof(*cft));

 	WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 2/6] hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations

[Mina Almasry]

Augements hugetlb_cgroup_charge_cgroup to be able to charge hugetlb
usage or hugetlb reservation counter.

Adds a new interface to uncharge a hugetlb_cgroup counter via
hugetlb_cgroup_uncharge_counter.

Integrates the counter with hugetlb_cgroup, via hugetlb_cgroup_init,
hugetlb_cgroup_have_usage, and hugetlb_cgroup_css_offline.

---
 include/linux/hugetlb_cgroup.h |  8 +++-
 mm/hugetlb.c                   |  3 +-
 mm/hugetlb_cgroup.c            | 80 ++++++++++++++++++++++++++++------
 3 files changed, 74 insertions(+), 17 deletions(-)

diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index 063962f6dfc6a..0725f809cd2d9 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -52,7 +52,8 @@ static inline bool hugetlb_cgroup_disabled(void)
 }

 extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
-					struct hugetlb_cgroup **ptr);
+					struct hugetlb_cgroup **ptr,
+					bool reserved);
 extern void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
 					 struct hugetlb_cgroup *h_cg,
 					 struct page *page);
@@ -60,6 +61,9 @@ extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
 					 struct page *page);
 extern void hugetlb_cgroup_uncharge_cgroup(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);
+
 extern void hugetlb_cgroup_file_init(void) __init;
 extern void hugetlb_cgroup_migrate(struct page *oldhpage,
 				   struct page *newhpage);
@@ -83,7 +87,7 @@ static inline bool hugetlb_cgroup_disabled(void)

 static inline int
 hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
-			     struct hugetlb_cgroup **ptr)
+			     struct hugetlb_cgroup **ptr, bool reserved)
 {
 	return 0;
 }
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 6d7296dd11b83..242cfeb7cc3e1 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2078,7 +2078,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
 			gbl_chg = 1;
 	}

-	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
+	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg,
+					   false);
 	if (ret)
 		goto out_subpool_put;

diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 51a72624bd1ff..bd9b58474be51 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -38,8 +38,8 @@ struct hugetlb_cgroup {
 static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

 static inline
-struct page_counter *hugetlb_cgroup_get_counter(struct hugetlb_cgroup *h_cg, int idx,
-				 bool reserved)
+struct page_counter *hugetlb_cgroup_get_counter(struct hugetlb_cgroup *h_cg,
+						int idx, bool reserved)
 {
 	if (reserved)
 		return  &h_cg->reserved_hugepage[idx];
@@ -74,8 +74,12 @@ static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
 	int idx;

 	for (idx = 0; idx < hugetlb_max_hstate; idx++) {
-		if (page_counter_read(&h_cg->hugepage[idx]))
+		if (page_counter_read(hugetlb_cgroup_get_counter(h_cg, idx,
+						true)) ||
+		    page_counter_read(hugetlb_cgroup_get_counter(h_cg, idx,
+				    false))) {
 			return true;
+		}
 	}
 	return false;
 }
@@ -86,18 +90,30 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
 	int idx;

 	for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
-		struct page_counter *counter = &h_cgroup->hugepage[idx];
 		struct page_counter *parent = NULL;
+		struct page_counter *reserved_parent = NULL;
 		unsigned long limit;
 		int ret;

-		if (parent_h_cgroup)
-			parent = &parent_h_cgroup->hugepage[idx];
-		page_counter_init(counter, parent);
+		if (parent_h_cgroup) {
+			parent = hugetlb_cgroup_get_counter(
+					parent_h_cgroup, idx, false);
+			reserved_parent = hugetlb_cgroup_get_counter(
+					parent_h_cgroup, idx, true);
+		}
+		page_counter_init(hugetlb_cgroup_get_counter(
+					h_cgroup, idx, false), parent);
+		page_counter_init(hugetlb_cgroup_get_counter(
+					h_cgroup, idx, true),
+				  reserved_parent);

 		limit = round_down(PAGE_COUNTER_MAX,
 				   1 << huge_page_order(&hstates[idx]));
-		ret = page_counter_set_max(counter, limit);
+
+		ret = page_counter_set_max(hugetlb_cgroup_get_counter(
+					h_cgroup, idx, false), limit);
+		ret = page_counter_set_max(hugetlb_cgroup_get_counter(
+					h_cgroup, idx, true), limit);
 		VM_BUG_ON(ret);
 	}
 }
@@ -127,6 +143,26 @@ static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
 	kfree(h_cgroup);
 }

+static void hugetlb_cgroup_move_parent_reservation(int idx,
+						   struct hugetlb_cgroup *h_cg)
+{
+	struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);
+
+	/* Move the reservation counters. */
+	if (!parent_hugetlb_cgroup(h_cg)) {
+		parent = root_h_cgroup;
+		/* root has no limit */
+		page_counter_charge(
+				&root_h_cgroup->reserved_hugepage[idx],
+				page_counter_read(hugetlb_cgroup_get_counter(
+						h_cg, idx, true)));
+	}
+
+	/* Take the pages off the local counter */
+	page_counter_cancel(hugetlb_cgroup_get_counter(h_cg, idx, true),
+			    page_counter_read(hugetlb_cgroup_get_counter(h_cg,
+					    idx, true)));
+}

 /*
  * Should be called with hugetlb_lock held.
@@ -181,6 +217,7 @@ static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state *css)
 	do {
 		for_each_hstate(h) {
 			spin_lock(&hugetlb_lock);
+			hugetlb_cgroup_move_parent_reservation(idx, h_cg);
 			list_for_each_entry(page, &h->hugepage_activelist, lru)
 				hugetlb_cgroup_move_parent(idx, h_cg, page);

@@ -192,7 +229,7 @@ static void hugetlb_cgroup_css_offline(struct cgroup_subsys_state *css)
 }

 int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
-				 struct hugetlb_cgroup **ptr)
+				 struct hugetlb_cgroup **ptr, bool reserved)
 {
 	int ret = 0;
 	struct page_counter *counter;
@@ -215,8 +252,11 @@ int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
 	}
 	rcu_read_unlock();

-	if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
+	if (!page_counter_try_charge(hugetlb_cgroup_get_counter(h_cg, idx,
+								reserved),
+				     nr_pages, &counter)) {
 		ret = -ENOMEM;
+	}
 	css_put(&h_cg->css);
 done:
 	*ptr = h_cg;
@@ -250,7 +290,9 @@ void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
 	if (unlikely(!h_cg))
 		return;
 	set_hugetlb_cgroup(page, NULL);
-	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
+	page_counter_uncharge(hugetlb_cgroup_get_counter(h_cg, idx, false),
+			nr_pages);
+
 	return;
 }

@@ -263,8 +305,17 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
 	if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
 		return;

-	page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
-	return;
+	page_counter_uncharge(hugetlb_cgroup_get_counter(h_cg, idx, false),
+			nr_pages);
+}
+
+void hugetlb_cgroup_uncharge_counter(struct page_counter *p,
+				     unsigned long nr_pages)
+{
+	if (hugetlb_cgroup_disabled() || !p)
+		return;
+
+	page_counter_uncharge(p, nr_pages);
 }

 static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
@@ -326,7 +377,8 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
 		/* Fall through. */
 	case HUGETLB_RES_LIMIT:
 		mutex_lock(&hugetlb_limit_mutex);
-		ret = page_counter_set_max(hugetlb_cgroup_get_counter(h_cg, idx, reserved),
+		ret = page_counter_set_max(hugetlb_cgroup_get_counter(h_cg, idx,
+								      reserved),
 					   nr_pages);
 		mutex_unlock(&hugetlb_limit_mutex);
 		break;
--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 3/6] hugetlb_cgroup: add reservation accounting for private mappings

[Mina Almasry]

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 128ff1aff1c93..536cb144cf484 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 242cfeb7cc3e1..7c2df7574cf50 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)
@@ -4535,6 +4559,7 @@ 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 */
@@ -4568,11 +4593,29 @@ 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 bd9b58474be51..1db97439bdb57 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)
--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 4/6] hugetlb_cgroup: add accounting for shared mappings

[Mina Almasry]

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

When a file_region entry is added to the resv_map via region_add, we
also charge the appropriate hugetlb_cgroup and put the pointer to that
in file_region->reservation_counter. This is slightly delicate since we
need to not modify the resv_map until we know that charging the
reservation has succeeded. 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 delete
the file_region entry in the resv_map, but also uncharge the
file_region->reservation_counter.

region_add() and region_chg() are heavily refactored to in this commit
to make the code easier to understand and remove duplication.

---
 mm/hugetlb.c | 443 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 280 insertions(+), 163 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c2df7574cf50..953e93359f021 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -242,208 +242,276 @@ 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;
+	unsigned long pages_per_hpage;
+#endif
 };

-/*
- * Add the huge page range represented by [f, t) to the reserve
- * map.  In the normal case, existing regions will be expanded
- * to accommodate the specified range.  Sufficient regions should
- * exist for expansion due to the previous call to region_chg
- * with the same range.  However, it is possible that region_del
- * could have been called after region_chg and modifed the map
- * in such a way that no region exists to be expanded.  In this
- * case, pull a region descriptor from the cache associated with
- * the map and use that for the new range.
- *
- * Return the number of new huge pages added to the map.  This
- * number is greater than or equal to zero.
+/* Helper that removes a struct file_region from the resv_map cache and returns
+ * it for use.
  */
-static long region_add(struct resv_map *resv, long f, long t)
+static struct file_region *get_file_region_entry_from_cache(
+		struct resv_map *resv, long from, long to)
 {
-	struct list_head *head = &resv->regions;
-	struct file_region *rg, *nrg, *trg;
-	long add = 0;
+	struct file_region *nrg = NULL;

-	spin_lock(&resv->lock);
-	/* Locate the region we are either in or before. */
-	list_for_each_entry(rg, head, link)
-		if (f <= rg->to)
-			break;
+	VM_BUG_ON(resv->region_cache_count <= 0);

-	/*
-	 * If no region exists which can be expanded to include the
-	 * specified range, the list must have been modified by an
-	 * interleving call to region_del().  Pull a region descriptor
-	 * from the cache and use it for this range.
-	 */
-	if (&rg->link == head || t < rg->from) {
-		VM_BUG_ON(resv->region_cache_count <= 0);
+	resv->region_cache_count--;
+	nrg = list_first_entry(&resv->region_cache, struct file_region,
+			link);
+	VM_BUG_ON(!nrg);
+	list_del(&nrg->link);

-		resv->region_cache_count--;
-		nrg = list_first_entry(&resv->region_cache, struct file_region,
-					link);
-		list_del(&nrg->link);
+	nrg->from = from;
+	nrg->to = to;

-		nrg->from = f;
-		nrg->to = t;
-		list_add(&nrg->link, rg->link.prev);
+	return nrg;
+}

-		add += t - f;
-		goto out_locked;
+/* Helper that records hugetlb_cgroup uncharge info. */
+static void record_hugetlb_cgroup_uncharge_info(struct hugetlb_cgroup *h_cg,
+		struct file_region *nrg, struct hstate *h)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+	if (h_cg) {
+		nrg->reservation_counter =
+			&h_cg->reserved_hugepage[hstate_index(h)];
+		nrg->pages_per_hpage = pages_per_huge_page(h);
 	}
+#endif
+}

-	/* Round our left edge to the current segment if it encloses us. */
-	if (f > rg->from)
-		f = rg->from;
+/* Must be called with resv->lock held. Calling this with dry_run == true will
+ * count the number of pages to be added but will not modify the linked list.
+ */
+static long add_reservations_in_range(struct resv_map *resv,
+		struct list_head *head, long f, long t,
+		struct hugetlb_cgroup *h_cg,
+		struct hstate *h,
+		bool dry_run)
+{
+	long add = 0;
+	long last_accounted_offset = f;
+	struct file_region *rg = NULL, *trg = NULL, *nrg = NULL;

-	/* Check for and consume any regions we now overlap with. */
-	nrg = rg;
-	list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
-		if (&rg->link == head)
-			break;
+	/* In this loop, we essentially handle an entry for the range
+	 * last_accounted_offset -> rg->from, at every iteration, with some
+	 * bounds checking.
+	 */
+	list_for_each_entry_safe(rg, trg, head, link) {
+		/* Skip irrelevant regions that start before our range. */
+		if (rg->from < f) {
+			/* If this region ends after the last accounted offset,
+			 * then we need to update last_accounted_offset.
+			 */
+			if (rg->to > last_accounted_offset)
+				last_accounted_offset = rg->to;
+			continue;
+		}
+
+		/* When we find a region that starts beyond our range, we've
+		 * finished.
+		 */
 		if (rg->from > t)
 			break;

-		/* If this area reaches higher then extend our area to
-		 * include it completely.  If this is not the first area
-		 * which we intend to reuse, free it. */
-		if (rg->to > t)
-			t = rg->to;
-		if (rg != nrg) {
-			/* Decrement return value by the deleted range.
-			 * Another range will span this area so that by
-			 * end of routine add will be >= zero
-			 */
-			add -= (rg->to - rg->from);
-			list_del(&rg->link);
-			kfree(rg);
+		/* Add an entry for last_accounted_offset -> rg->from, and
+		 * update last_accounted_offset.
+		 */
+		if (rg->from > last_accounted_offset) {
+			add += rg->from - last_accounted_offset;
+			if (!dry_run) {
+				nrg = get_file_region_entry_from_cache(resv,
+						last_accounted_offset,
+						rg->from);
+				record_hugetlb_cgroup_uncharge_info(h_cg, nrg,
+						h);
+				list_add(&nrg->link, rg->link.prev);
+			}
+		}
+
+		last_accounted_offset = rg->to;
+
+		if (!dry_run) {
+			if (rg->from == rg->to) {
+				list_del(&rg->link);
+				kfree(rg);
+			}
 		}
 	}

-	add += (nrg->from - f);		/* Added to beginning of region */
-	nrg->from = f;
-	add += t - nrg->to;		/* Added to end of region */
-	nrg->to = t;
+	/* Handle the case where our range extends beyond
+	 * last_accounted_offset.
+	 */
+	if (last_accounted_offset < t) {
+		add += t - last_accounted_offset;
+		if (!dry_run) {
+			nrg = get_file_region_entry_from_cache(resv,
+					last_accounted_offset, t);
+			record_hugetlb_cgroup_uncharge_info(h_cg, nrg, h);
+			list_add(&nrg->link, rg->link.prev);
+		}
+		last_accounted_offset = t;
+	}

-out_locked:
-	resv->adds_in_progress--;
-	spin_unlock(&resv->lock);
-	VM_BUG_ON(add < 0);
 	return add;
 }

-/*
- * Examine the existing reserve map and determine how many
- * huge pages in the specified range [f, t) are NOT currently
- * represented.  This routine is called before a subsequent
- * call to region_add that will actually modify the reserve
- * map to add the specified range [f, t).  region_chg does
- * not change the number of huge pages represented by the
- * map.  However, if the existing regions in the map can not
- * be expanded to represent the new range, a new file_region
- * structure is added to the map as a placeholder.  This is
- * so that the subsequent region_add call will have all the
- * regions it needs and will not fail.
- *
- * Upon entry, region_chg will also examine the cache of region descriptors
- * associated with the map.  If there are not enough descriptors cached, one
- * will be allocated for the in progress add operation.
+static int charge_cgroup_if_shared_mapping(struct resv_map *resv,
+		struct hstate *h, long nr_pages, struct hugetlb_cgroup **h_cg)
+{
+	int ret = 0;
+#ifdef CONFIG_CGROUP_HUGETLB
+	/*
+	 * If res->reservation_counter is NULL, then it means this is
+	 * a shared mapping, and hugetlb cgroup accounting should be
+	 * done on the file_region entries inside resv_map.
+	 */
+	if (!resv->reservation_counter) {
+		ret = hugetlb_cgroup_charge_cgroup(
+				hstate_index(h),
+				nr_pages * pages_per_huge_page(h),
+				h_cg, true);
+	}
+#endif
+	return ret;
+}
+
+/* This function will examine resv_map and deterimine how many huge pages are
+ * NOT currently represented. Then it will make sure resv->region_cache_count
+ * has enough entries in it to satisfy a following add_reservations_in_range
+ * call.
  *
- * Returns the number of huge pages that need to be added to the existing
- * reservation map for the range [f, t).  This number is greater or equal to
- * zero.  -ENOMEM is returned if a new file_region structure or cache entry
- * is needed and can not be allocated.
+ * Returns the number of hugepages pages NOT respresented on success with
+ * resv->lock held. Returns -ENOMEM if it needs to allocate a region_cache item
+ * and fails to do so, with the lock NOT held.
  */
-static long region_chg(struct resv_map *resv, long f, long t)
+static long allocate_enough_cache_for_range_and_lock(struct resv_map *resv,
+		long f, long t)
 {
 	struct list_head *head = &resv->regions;
-	struct file_region *rg, *nrg = NULL;
+	struct file_region *trg = NULL;
 	long chg = 0;

 retry:
 	spin_lock(&resv->lock);
-retry_locked:
-	resv->adds_in_progress++;
+
+	/* Count how many hugepages in this range are NOT respresented. */
+	chg = add_reservations_in_range(resv, head, f, t, NULL, NULL, true);

 	/*
 	 * Check for sufficient descriptors in the cache to accommodate
-	 * the number of in progress add operations.
+	 * the number of in progress add operations. There must be at least
+	 * 1 extra in the cache.
 	 */
-	if (resv->adds_in_progress > resv->region_cache_count) {
-		struct file_region *trg;
-
-		VM_BUG_ON(resv->adds_in_progress - resv->region_cache_count > 1);
+	if (resv->region_cache_count < chg + 1) {
 		/* Must drop lock to allocate a new descriptor. */
-		resv->adds_in_progress--;
 		spin_unlock(&resv->lock);

-		trg = kmalloc(sizeof(*trg), GFP_KERNEL);
-		if (!trg) {
-			kfree(nrg);
-			return -ENOMEM;
-		}
+		while (resv->region_cache_count < chg + 1) {
+			trg = kmalloc(sizeof(*trg), GFP_KERNEL);
+			if (!trg)
+				return -ENOMEM;

-		spin_lock(&resv->lock);
-		list_add(&trg->link, &resv->region_cache);
-		resv->region_cache_count++;
-		goto retry_locked;
+			spin_lock(&resv->lock);
+			list_add(&trg->link, &resv->region_cache);
+			resv->region_cache_count++;
+			spin_unlock(&resv->lock);
+		}
+		goto retry;
 	}

-	/* Locate the region we are before or in. */
-	list_for_each_entry(rg, head, link)
-		if (f <= rg->to)
-			break;
+	return chg;
+}

-	/* If we are below the current region then a new region is required.
-	 * Subtle, allocate a new region at the position but make it zero
-	 * size such that we can guarantee to record the reservation. */
-	if (&rg->link == head || t < rg->from) {
-		if (!nrg) {
-			resv->adds_in_progress--;
-			spin_unlock(&resv->lock);
-			nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
-			if (!nrg)
-				return -ENOMEM;
+/*
+ * Add the huge page range represented by [f, t) to the reserve
+ * map.  In the normal case, existing regions will be taken off
+ * the cache to accommodate the specified range.  Sufficient
+ * regions should exist in the cache due to the previous call
+ * to region_chg with the same range, but we still check we have
+ * enough regions in the cache anyway, since something else could
+ * have consumed our regions.
+ *
+ * Return the number of new huge pages added to the map.  This
+ * number is greater than or equal to zero.  If for some reason
+ * we don't have enough entries in the cache, try to allocate
+ * more regions, and fail, we return -ENOMEM.
+ */
+static long region_add(struct hstate *h, struct resv_map *resv, long f, long t)
+{
+	struct list_head *head = &resv->regions;
+	long chg = 0, add = 0;
+	struct hugetlb_cgroup *h_cg = NULL;
+	int ret = 0;

-			nrg->from = f;
-			nrg->to   = f;
-			INIT_LIST_HEAD(&nrg->link);
-			goto retry;
-		}
+	/* Count how many charges we will need to do. Locks resv->lock on
+	 * success.
+	 */
+	chg = allocate_enough_cache_for_range_and_lock(resv, f, t);

-		list_add(&nrg->link, rg->link.prev);
-		chg = t - f;
-		goto out_nrg;
+	if (chg < 0) {
+		ret = chg;
+		spin_lock(&resv->lock);
+		goto out_locked;
 	}

-	/* Round our left edge to the current segment if it encloses us. */
-	if (f > rg->from)
-		f = rg->from;
-	chg = t - f;
+	ret = charge_cgroup_if_shared_mapping(resv, h, chg, &h_cg);

-	/* Check for and consume any regions we now overlap with. */
-	list_for_each_entry(rg, rg->link.prev, link) {
-		if (&rg->link == head)
-			break;
-		if (rg->from > t)
-			goto out;
+	if (ret)
+		goto out_locked;

-		/* We overlap with this area, if it extends further than
-		 * us then we must extend ourselves.  Account for its
-		 * existing reservation. */
-		if (rg->to > t) {
-			chg += rg->to - t;
-			t = rg->to;
-		}
-		chg -= rg->to - rg->from;
-	}
+	add = add_reservations_in_range(resv, head, f, t, h_cg, h,
+			false);

-out:
+	/*
+	 * If these aren't equal, then there is a bug with
+	 * consume_regions_we_overlap_with, and we're charging the wrong amount
+	 * of memory. This should never happen as we are holding to the lock
+	 * between the 2 add_reservations_in_range calls.
+	 */
+	WARN_ON(add != chg);
+
+out_locked:
+	resv->adds_in_progress = 0;
 	spin_unlock(&resv->lock);
-	/*  We already know we raced and no longer need the new region */
-	kfree(nrg);
-	return chg;
-out_nrg:
+	if (ret)
+		return ret;
+	VM_BUG_ON(add < 0);
+	return add;
+}
+
+/*
+ * Examine the existing reserve map and determine how many
+ * huge pages in the specified range [f, t) are NOT currently
+ * represented.  This routine is called before a subsequent
+ * call to region_add that will fill region_cache with enough
+ * entries to add the specified range [f, t).  region_chg does
+ * not change the number of huge pages represented by the
+ * map.
+ *
+ * Returns the number of huge pages that need to be added to the existing
+ * reservation map for the range [f, t).  This number is greater or equal to
+ * zero.  -ENOMEM is returned if a new file_region structure or cache entry
+ * is needed and can not be allocated.
+ */
+static long region_chg(struct resv_map *resv, long f, long t)
+{
+	long chg = allocate_enough_cache_for_range_and_lock(resv,
+			f, t);
+
+	if (chg < 0)
+		return chg;
+
+	resv->adds_in_progress = chg;
+
 	spin_unlock(&resv->lock);
 	return chg;
 }
@@ -463,10 +531,43 @@ static void region_abort(struct resv_map *resv, long f, long t)
 {
 	spin_lock(&resv->lock);
 	VM_BUG_ON(!resv->region_cache_count);
-	resv->adds_in_progress--;
+	resv->adds_in_progress = 0;
 	spin_unlock(&resv->lock);
 }

+static void get_hugetlb_cgroup_info(struct page_counter **reservation_counter,
+		unsigned long *pages_per_hpage, struct file_region *nrg)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+	/*
+	 * Save counter information from the deleted
+	 * node, in case we need to do an uncharge.
+	 */
+	*reservation_counter = nrg->reservation_counter;
+	*pages_per_hpage = nrg->pages_per_hpage;
+#endif
+}
+
+static void uncharge_cgroup_if_shared_mapping(struct resv_map *resv,
+		struct page_counter *reservation_counter,
+		unsigned long pages_per_hpage,
+		unsigned long nr_pages)
+{
+#ifdef CONFIG_CGROUP_HUGETLB
+	/*
+	 * If resv->reservation_counter is NULL, then this is shared
+	 * reservation, and the reserved memory is tracked in the file_struct
+	 * entries inside of resv_map. So we need to uncharge the memory here.
+	 */
+	if (reservation_counter && pages_per_hpage && nr_pages > 0 &&
+	    !resv->reservation_counter) {
+		hugetlb_cgroup_uncharge_counter(
+				reservation_counter,
+				nr_pages * pages_per_hpage);
+	}
+#endif
+}
+
 /*
  * Delete the specified range [f, t) from the reserve map.  If the
  * t parameter is LONG_MAX, this indicates that ALL regions after f
@@ -487,6 +588,8 @@ static long region_del(struct resv_map *resv, long f, long t)
 	struct file_region *rg, *trg;
 	struct file_region *nrg = NULL;
 	long del = 0;
+	struct page_counter *reservation_counter = NULL;
+	unsigned long pages_per_hpage = 0;

 retry:
 	spin_lock(&resv->lock);
@@ -543,6 +646,9 @@ 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;
+			get_hugetlb_cgroup_info(&reservation_counter,
+					&pages_per_hpage,
+					rg);
 			list_del(&rg->link);
 			kfree(rg);
 			continue;
@@ -559,6 +665,9 @@ static long region_del(struct resv_map *resv, long f, long t)

 	spin_unlock(&resv->lock);
 	kfree(nrg);
+
+	uncharge_cgroup_if_shared_mapping(resv, reservation_counter,
+			pages_per_hpage, del);
 	return del;
 }

@@ -1930,7 +2039,7 @@ static long __vma_reservation_common(struct hstate *h,
 		ret = region_chg(resv, idx, idx + 1);
 		break;
 	case VMA_COMMIT_RESV:
-		ret = region_add(resv, idx, idx + 1);
+		ret = region_add(h, resv, idx, idx + 1);
 		break;
 	case VMA_END_RESV:
 		region_abort(resv, idx, idx + 1);
@@ -1938,7 +2047,7 @@ 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);
+			ret = region_add(h, resv, idx, idx + 1);
 		else {
 			region_abort(resv, idx, idx + 1);
 			ret = region_del(resv, idx, idx + 1);
@@ -4555,7 +4664,7 @@ int hugetlb_reserve_pages(struct inode *inode,
 					struct vm_area_struct *vma,
 					vm_flags_t vm_flags)
 {
-	long ret, chg;
+	long ret, chg, add;
 	struct hstate *h = hstate_inode(inode);
 	struct hugepage_subpool *spool = subpool_inode(inode);
 	struct resv_map *resv_map;
@@ -4643,9 +4752,7 @@ 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;
 	}

 	/*
@@ -4660,7 +4767,12 @@ int hugetlb_reserve_pages(struct inode *inode,
 	 * else has to be done for private mappings here
 	 */
 	if (!vma || vma->vm_flags & VM_MAYSHARE) {
-		long add = region_add(resv_map, from, to);
+		add = region_add(h, resv_map, from, to);
+		if (add < 0) {
+			ret = -ENOMEM;
+			goto out_acct_memory;
+		}
+

 		if (unlikely(chg > add)) {
 			/*
@@ -4678,10 +4790,15 @@ int hugetlb_reserve_pages(struct inode *inode,
 		}
 	}
 	return 0;
+out_acct_memory:
+	hugetlb_acct_memory(h, -gbl_reserve);
+out_put_pages:
+	/* put back original number of pages, chg */
+	(void)hugepage_subpool_put_pages(spool, chg);
 out_err:
 	if (!vma || vma->vm_flags & VM_MAYSHARE)
-		/* Don't call region_abort if region_chg failed */
-		if (chg >= 0)
+		/* Don't call region_abort if region_chg or region_add failed */
+		if (chg >= 0 && add >= 0)
 			region_abort(resv_map, from, to);
 	if (vma && is_vma_resv_set(vma, HPAGE_RESV_OWNER))
 		kref_put(&resv_map->refs, resv_map_release);
--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 5/6] hugetlb_cgroup: Add hugetlb_cgroup reservation tests

[Mina Almasry]

The tests use both shared and private mapped hugetlb memory, and
monitors the hugetlb usage counter as well as the hugetlb reservation
counter. They test different configurations such as hugetlb memory usage
via hugetlbfs, or MAP_HUGETLB, or shmget/shmat, and with and without
MAP_POPULATE.

---
 tools/testing/selftests/vm/.gitignore         |   1 +
 tools/testing/selftests/vm/Makefile           |   4 +
 .../selftests/vm/charge_reserved_hugetlb.sh   | 438 ++++++++++++++++++
 .../selftests/vm/write_hugetlb_memory.sh      |  22 +
 .../testing/selftests/vm/write_to_hugetlbfs.c | 252 ++++++++++
 5 files changed, 717 insertions(+)
 create mode 100755 tools/testing/selftests/vm/charge_reserved_hugetlb.sh
 create mode 100644 tools/testing/selftests/vm/write_hugetlb_memory.sh
 create mode 100644 tools/testing/selftests/vm/write_to_hugetlbfs.c

diff --git a/tools/testing/selftests/vm/.gitignore b/tools/testing/selftests/vm/.gitignore
index 31b3c98b6d34d..d3bed9407773c 100644
--- a/tools/testing/selftests/vm/.gitignore
+++ b/tools/testing/selftests/vm/.gitignore
@@ -14,3 +14,4 @@ virtual_address_range
 gup_benchmark
 va_128TBswitch
 map_fixed_noreplace
+write_to_hugetlbfs
diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 9534dc2bc9295..8d37d5409b52c 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -18,6 +18,7 @@ TEST_GEN_FILES += transhuge-stress
 TEST_GEN_FILES += userfaultfd
 TEST_GEN_FILES += va_128TBswitch
 TEST_GEN_FILES += virtual_address_range
+TEST_GEN_FILES += write_to_hugetlbfs

 TEST_PROGS := run_vmtests

@@ -29,3 +30,6 @@ include ../lib.mk
 $(OUTPUT)/userfaultfd: LDLIBS += -lpthread

 $(OUTPUT)/mlock-random-test: LDLIBS += -lcap
+
+# Why does adding $(OUTPUT)/ like above not apply this flag..?
+write_to_hugetlbfs: CFLAGS += -static
diff --git a/tools/testing/selftests/vm/charge_reserved_hugetlb.sh b/tools/testing/selftests/vm/charge_reserved_hugetlb.sh
new file mode 100755
index 0000000000000..bf0b6dcec9977
--- /dev/null
+++ b/tools/testing/selftests/vm/charge_reserved_hugetlb.sh
@@ -0,0 +1,438 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+cgroup_path=/dev/cgroup/memory
+if [[ ! -e $cgroup_path ]]; then
+      mkdir -p $cgroup_path
+      mount -t cgroup -o hugetlb,memory cgroup $cgroup_path
+fi
+
+cleanup () {
+	echo $$ > $cgroup_path/tasks
+
+	set +e
+	if [[ "$(pgrep write_to_hugetlbfs)" != "" ]]; then
+	      kill -2 write_to_hugetlbfs
+	      # Wait for hugetlbfs memory to get depleted.
+	      sleep 0.5
+	fi
+	set -e
+
+	if [[ -e /mnt/huge ]]; then
+	      rm -rf /mnt/huge/*
+	      umount /mnt/huge || echo error
+	      rmdir /mnt/huge
+	fi
+	if [[ -e $cgroup_path/hugetlb_cgroup_test ]]; then
+	      rmdir $cgroup_path/hugetlb_cgroup_test
+	fi
+	if [[ -e $cgroup_path/hugetlb_cgroup_test1 ]]; then
+	      rmdir $cgroup_path/hugetlb_cgroup_test1
+	fi
+	if [[ -e $cgroup_path/hugetlb_cgroup_test2 ]]; then
+	      rmdir $cgroup_path/hugetlb_cgroup_test2
+	fi
+	echo 0 > /proc/sys/vm/nr_hugepages
+	echo CLEANUP DONE
+}
+
+cleanup
+
+function expect_equal() {
+      local expected="$1"
+      local actual="$2"
+      local error="$3"
+
+      if [[ "$expected" != "$actual" ]]; then
+	    echo "expected ($expected) != actual ($actual): $3"
+	    cleanup
+	    exit 1
+      fi
+}
+
+function setup_cgroup() {
+      local name="$1"
+      local cgroup_limit="$2"
+      local reservation_limit="$3"
+
+      mkdir $cgroup_path/$name
+
+      echo writing cgroup limit: "$cgroup_limit"
+      echo "$cgroup_limit" > $cgroup_path/$name/hugetlb.2MB.limit_in_bytes
+
+      echo writing reseravation limit: "$reservation_limit"
+      echo "$reservation_limit" > \
+	    $cgroup_path/$name/hugetlb.2MB.reservation_limit_in_bytes
+}
+
+function write_hugetlbfs_and_get_usage() {
+      local cgroup="$1"
+      local size="$2"
+      local populate="$3"
+      local write="$4"
+      local path="$5"
+      local method="$6"
+      local private="$7"
+      local expect_failure="$8"
+
+      # Function return values.
+      reservation_failed=0
+      oom_killed=0
+      hugetlb_difference=0
+      reserved_difference=0
+
+      local hugetlb_usage=$cgroup_path/$cgroup/hugetlb.2MB.usage_in_bytes
+      local reserved_usage=$cgroup_path/$cgroup/hugetlb.2MB.reservation_usage_in_bytes
+
+      local hugetlb_before=$(cat $hugetlb_usage)
+      local reserved_before=$(cat $reserved_usage)
+
+      echo
+      echo Starting:
+      echo hugetlb_usage="$hugetlb_before"
+      echo reserved_usage="$reserved_before"
+      echo expect_failure is "$expect_failure"
+
+      set +e
+      if [[ "$method" == "1" ]] || [[ "$method" == 2 ]] || \
+	    [[ "$private" == "-r" ]] && [[ "$expect_failure" != 1 ]]; then
+	    bash write_hugetlb_memory.sh "$size" "$populate" "$write" \
+		  "$cgroup"  "$path" "$method" "$private" "-l" &
+
+	    local write_result=$?
+	    # This sleep is to make sure that the script above has had enough
+	    # time to do its thing, since it runs in the background. This may
+	    # cause races...
+	    sleep 0.5
+	    echo write_result is $write_result
+      else
+	    bash write_hugetlb_memory.sh "$size" "$populate" "$write" \
+		  "$cgroup"  "$path" "$method" "$private"
+	    local write_result=$?
+      fi
+      set -e
+
+      if [[ "$write_result" == 1 ]]; then
+	    reservation_failed=1
+      fi
+
+      # On linus/master, the above process gets SIGBUS'd on oomkill, with
+      # return code 135. On earlier kernels, it gets actual oomkill, with return
+      # code 137, so just check for both conditions incase we're testing against
+      # an earlier kernel.
+      if [[ "$write_result" == 135 ]] || [[ "$write_result" == 137 ]]; then
+	    oom_killed=1
+      fi
+
+      local hugetlb_after=$(cat $hugetlb_usage)
+      local reserved_after=$(cat $reserved_usage)
+
+      echo After write:
+      echo hugetlb_usage="$hugetlb_after"
+      echo reserved_usage="$reserved_after"
+
+      hugetlb_difference=$(($hugetlb_after - $hugetlb_before))
+      reserved_difference=$(($reserved_after - $reserved_before))
+}
+
+function cleanup_hugetlb_memory() {
+      set +e
+      if [[ "$(pgrep write_to_hugetlbfs)" != "" ]]; then
+	    echo kiling write_to_hugetlbfs
+	    killall -2 write_to_hugetlbfs
+	    # Wait for hugetlbfs memory to get depleted.
+	    sleep 0.5
+      fi
+      set -e
+
+      if [[ -e /mnt/huge ]]; then
+	    rm -rf /mnt/huge/*
+	      umount /mnt/huge
+	      rmdir /mnt/huge
+      fi
+}
+
+function run_test() {
+      local size="$1"
+      local populate="$2"
+      local write="$3"
+      local cgroup_limit="$4"
+      local reservation_limit="$5"
+      local nr_hugepages="$6"
+      local method="$7"
+      local private="$8"
+      local expect_failure="$9"
+
+      # Function return values.
+      hugetlb_difference=0
+      reserved_difference=0
+      reservation_failed=0
+      oom_killed=0
+
+      echo nr hugepages = "$nr_hugepages"
+      echo "$nr_hugepages" > /proc/sys/vm/nr_hugepages
+
+      setup_cgroup "hugetlb_cgroup_test" "$cgroup_limit" "$reservation_limit"
+
+      mkdir -p /mnt/huge
+      mount -t hugetlbfs \
+	    -o pagesize=2M,size=256M none /mnt/huge
+
+      write_hugetlbfs_and_get_usage "hugetlb_cgroup_test" "$size" "$populate" \
+	    "$write" "/mnt/huge/test" "$method" "$private" "$expect_failure"
+
+      cleanup_hugetlb_memory
+
+      local final_hugetlb=$(cat $cgroup_path/hugetlb_cgroup_test/hugetlb.2MB.usage_in_bytes)
+      local final_reservation=$(cat $cgroup_path/hugetlb_cgroup_test/hugetlb.2MB.reservation_usage_in_bytes)
+
+      expect_equal "0" "$final_hugetlb" "final hugetlb is not zero"
+      expect_equal "0" "$final_reservation" "final reservation is not zero"
+}
+
+function run_multiple_cgroup_test() {
+      local size1="$1"
+      local populate1="$2"
+      local write1="$3"
+      local cgroup_limit1="$4"
+      local reservation_limit1="$5"
+
+      local size2="$6"
+      local populate2="$7"
+      local write2="$8"
+      local cgroup_limit2="$9"
+      local reservation_limit2="${10}"
+
+      local nr_hugepages="${11}"
+      local method="${12}"
+      local private="${13}"
+      local expect_failure="${14}"
+
+      # Function return values.
+      hugetlb_difference1=0
+      reserved_difference1=0
+      reservation_failed1=0
+      oom_killed1=0
+
+      hugetlb_difference2=0
+      reserved_difference2=0
+      reservation_failed2=0
+      oom_killed2=0
+
+
+      echo nr hugepages = "$nr_hugepages"
+      echo "$nr_hugepages" > /proc/sys/vm/nr_hugepages
+
+      setup_cgroup "hugetlb_cgroup_test1" "$cgroup_limit1" "$reservation_limit1"
+      setup_cgroup "hugetlb_cgroup_test2" "$cgroup_limit2" "$reservation_limit2"
+
+      mkdir -p /mnt/huge
+      mount -t hugetlbfs \
+	    -o pagesize=2M,size=256M none /mnt/huge
+
+      write_hugetlbfs_and_get_usage "hugetlb_cgroup_test1" "$size1" \
+	    "$populate1" "$write1" "/mnt/huge/test1" "$method" "$private" \
+	    "$expect_failure"
+
+      hugetlb_difference1=$hugetlb_difference
+      reserved_difference1=$reserved_difference
+      reservation_failed1=$reservation_failed
+      oom_killed1=$oom_killed
+
+      local cgroup1_hugetlb_usage=$cgroup_path/hugetlb_cgroup_test1/hugetlb.2MB.usage_in_bytes
+      local cgroup1_reservation_usage=$cgroup_path/hugetlb_cgroup_test1/hugetlb.2MB.reservation_usage_in_bytes
+      local cgroup2_hugetlb_usage=$cgroup_path/hugetlb_cgroup_test2/hugetlb.2MB.usage_in_bytes
+      local cgroup2_reservation_usage=$cgroup_path/hugetlb_cgroup_test2/hugetlb.2MB.reservation_usage_in_bytes
+
+      local usage_before_second_write=$(cat $cgroup1_hugetlb_usage)
+      local reservation_usage_before_second_write=$(cat \
+	    $cgroup1_reservation_usage)
+
+      write_hugetlbfs_and_get_usage "hugetlb_cgroup_test2" "$size2" \
+	    "$populate2" "$write2" "/mnt/huge/test2" "$method" "$private" \
+	    "$expect_failure"
+
+      hugetlb_difference2=$hugetlb_difference
+      reserved_difference2=$reserved_difference
+      reservation_failed2=$reservation_failed
+      oom_killed2=$oom_killed
+
+      expect_equal "$usage_before_second_write" \
+	    "$(cat $cgroup1_hugetlb_usage)" "Usage changed."
+      expect_equal "$reservation_usage_before_second_write" \
+	    "$(cat $cgroup1_reservation_usage)" "Reservation usage changed."
+
+      cleanup_hugetlb_memory
+
+      local final_hugetlb=$(cat $cgroup1_hugetlb_usage)
+      local final_reservation=$(cat $cgroup1_reservation_usage)
+
+      expect_equal "0" "$final_hugetlb" \
+	    "hugetlbt_cgroup_test1 final hugetlb is not zero"
+      expect_equal "0" "$final_reservation" \
+	    "hugetlbt_cgroup_test1 final reservation is not zero"
+
+      local final_hugetlb=$(cat $cgroup2_hugetlb_usage)
+      local final_reservation=$(cat $cgroup2_reservation_usage)
+
+      expect_equal "0" "$final_hugetlb" \
+	    "hugetlb_cgroup_test2 final hugetlb is not zero"
+      expect_equal "0" "$final_reservation" \
+	    "hugetlb_cgroup_test2 final reservation is not zero"
+}
+
+for private in "" "-r" ; do
+for populate in  "" "-o"; do
+for method in 0 1 2; do
+
+# Skip mmap(MAP_HUGETLB | MAP_SHARED). Doesn't seem to be supported.
+if [[ "$method" == 1 ]] && [[ "$private" == "" ]]; then
+      continue
+fi
+
+# Skip populated shmem tests. Doesn't seem to be supported.
+if [[ "$method" == 2"" ]] && [[ "$populate" == "-o" ]]; then
+      continue
+fi
+
+cleanup
+echo
+echo
+echo
+echo Test normal case.
+echo private=$private, populate=$populate, method=$method
+run_test $((10 * 1024 * 1024)) "$populate" "" $((20 * 1024 * 1024)) \
+      $((20 * 1024 * 1024)) 10 "$method" "$private" "0"
+
+echo Memory charged to hugtlb=$hugetlb_difference
+echo Memory charged to reservation=$reserved_difference
+
+if [[ "$populate" == "-o" ]]; then
+      expect_equal "$((10 * 1024 * 1024))" "$hugetlb_difference" \
+	    "Reserved memory charged to hugetlb cgroup."
+else
+      expect_equal "0" "$hugetlb_difference" \
+	    "Reserved memory charged to hugetlb cgroup."
+fi
+
+expect_equal "$((10 * 1024 * 1024))" "$reserved_difference" \
+      "Reserved memory not charged to reservation usage."
+echo 'PASS'
+
+cleanup
+echo
+echo
+echo
+echo Test normal case with write.
+echo private=$private, populate=$populate, method=$method
+run_test $((10 * 1024 * 1024)) "$populate" '-w' $((20 * 1024 * 1024)) \
+      $((20 * 1024 * 1024)) 10 "$method" "$private" "0"
+
+echo Memory charged to hugtlb=$hugetlb_difference
+echo Memory charged to reservation=$reserved_difference
+
+expect_equal "$((10 * 1024 * 1024))" "$hugetlb_difference" \
+      "Reserved memory charged to hugetlb cgroup."
+expect_equal "$((10 * 1024 * 1024))" "$reserved_difference" \
+      "Reserved memory not charged to reservation usage."
+echo 'PASS'
+
+
+cleanup
+echo
+echo
+echo
+echo Test more than reservation case.
+echo private=$private, populate=$populate, method=$method
+run_test "$((10 * 1024 * 1024))" "$populate" '' "$((20 * 1024 * 1024))" \
+      "$((5 * 1024 * 1024))" "10" "$method" "$private" "1"
+
+expect_equal "1" "$reservation_failed" "Reservation succeeded."
+echo 'PASS'
+
+cleanup
+
+echo
+echo
+echo
+echo Test more than cgroup limit case.
+echo private=$private, populate=$populate, method=$method
+
+# Not sure if shm memory can be cleaned up when the process gets sigbus'd.
+if [[ "$method" != 2 ]]; then
+      run_test $((10 * 1024 * 1024)) "$populate" "-w" $((5 * 1024 * 1024)) \
+	    $((20 * 1024 * 1024)) 10 "$method" "$private" "1"
+
+      expect_equal "1" "$oom_killed" "Not oom killed."
+fi
+echo 'PASS'
+
+cleanup
+
+echo
+echo
+echo
+echo Test normal case, multiple cgroups.
+echo private=$private, populate=$populate, method=$method
+run_multiple_cgroup_test "$((6 * 1024 * 1024))" "$populate" "" \
+      "$((20 * 1024 * 1024))" "$((20 * 1024 * 1024))" "$((10 * 1024 * 1024))" \
+      "$populate" "" "$((20 * 1024 * 1024))" "$((20 * 1024 * 1024))" "10" \
+      "$method" "$private" "0"
+
+echo Memory charged to hugtlb1=$hugetlb_difference1
+echo Memory charged to reservation1=$reserved_difference1
+echo Memory charged to hugtlb2=$hugetlb_difference2
+echo Memory charged to reservation2=$reserved_difference2
+
+expect_equal "$((6 * 1024 * 1024))" "$reserved_difference1" \
+      "Incorrect reservations charged to cgroup 1."
+expect_equal "$((10 * 1024 * 1024))" "$reserved_difference2" \
+      "Incorrect reservation charged to cgroup 2."
+if [[ "$populate" == "-o" ]]; then
+      expect_equal "$((6 * 1024 * 1024))" "$hugetlb_difference1" \
+	    "Incorrect hugetlb charged to cgroup 1."
+      expect_equal "$((10 * 1024 * 1024))" "$hugetlb_difference2" \
+	    "Incorrect hugetlb charged to cgroup 2."
+else
+      expect_equal "0" "$hugetlb_difference1" \
+	    "Incorrect hugetlb charged to cgroup 1."
+      expect_equal "0" "$hugetlb_difference2" \
+	    "Incorrect hugetlb charged to cgroup 2."
+fi
+echo 'PASS'
+
+cleanup
+echo
+echo
+echo
+echo Test normal case with write, multiple cgroups.
+echo private=$private, populate=$populate, method=$method
+run_multiple_cgroup_test "$((6 * 1024 * 1024))" "$populate" "-w" \
+      "$((20 * 1024 * 1024))" "$((20 * 1024 * 1024))" "$((10 * 1024 * 1024))" \
+      "$populate" "-w" "$((20 * 1024 * 1024))" "$((20 * 1024 * 1024))" "10" \
+      "$method" "$private" "0"
+
+echo Memory charged to hugtlb1=$hugetlb_difference1
+echo Memory charged to reservation1=$reserved_difference1
+echo Memory charged to hugtlb2=$hugetlb_difference2
+echo Memory charged to reservation2=$reserved_difference2
+
+expect_equal "$((6 * 1024 * 1024))" "$hugetlb_difference1" \
+      "Incorrect hugetlb charged to cgroup 1."
+expect_equal "$((6 * 1024 * 1024))" "$reserved_difference1" \
+      "Incorrect reservation charged to cgroup 1."
+expect_equal "$((10 * 1024 * 1024))" "$hugetlb_difference2" \
+      "Incorrect hugetlb charged to cgroup 2."
+expect_equal "$((10 * 1024 * 1024))" "$reserved_difference2" \
+      "Incorrected reservation charged to cgroup 2."
+
+echo 'PASS'
+
+done # private
+done # populate
+done # method
+
+umount $cgroup_path
+rmdir $cgroup_path
diff --git a/tools/testing/selftests/vm/write_hugetlb_memory.sh b/tools/testing/selftests/vm/write_hugetlb_memory.sh
new file mode 100644
index 0000000000000..08f5fa5527cfd
--- /dev/null
+++ b/tools/testing/selftests/vm/write_hugetlb_memory.sh
@@ -0,0 +1,22 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+size=$1
+populate=$2
+write=$3
+cgroup=$4
+path=$5
+method=$6
+private=$7
+want_sleep=$8
+
+echo "Putting task in cgroup '$cgroup'"
+echo $$ > /dev/cgroup/memory/"$cgroup"/tasks
+
+echo "Method is $method"
+
+set +e
+./write_to_hugetlbfs -p "$path" -s "$size" "$write" "$populate" -m "$method" \
+      "$private" "$want_sleep"
diff --git a/tools/testing/selftests/vm/write_to_hugetlbfs.c b/tools/testing/selftests/vm/write_to_hugetlbfs.c
new file mode 100644
index 0000000000000..f02a897427a97
--- /dev/null
+++ b/tools/testing/selftests/vm/write_to_hugetlbfs.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * This program reserves and uses hugetlb memory, supporting a bunch of
+ * scenorios needed by the charged_reserved_hugetlb.sh test.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/shm.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+
+/* Global definitions. */
+enum method {
+	HUGETLBFS,
+	MMAP_MAP_HUGETLB,
+	SHM,
+	MAX_METHOD
+};
+
+
+/* Global variables. */
+static const char *self;
+static char *shmaddr;
+static int shmid;
+
+/*
+ * Show usage and exit.
+ */
+static void exit_usage(void)
+{
+
+	printf("Usage: %s -p <path to hugetlbfs file> -s <size to map> "
+		"[-m <0=hugetlbfs | 1=mmap(MAP_HUGETLB)>] [-l] [-r] "
+		"[-o] [-w]\n", self);
+	exit(EXIT_FAILURE);
+}
+
+void sig_handler(int signo)
+{
+	printf("Received %d.\n", signo);
+	if (signo == SIGINT) {
+		printf("Deleting the memory\n");
+		if (shmdt((const void *)shmaddr) != 0) {
+			perror("Detach failure");
+			shmctl(shmid, IPC_RMID, NULL);
+			exit(4);
+		}
+
+		shmctl(shmid, IPC_RMID, NULL);
+		printf("Done deleting the memory\n");
+	}
+	exit(2);
+}
+
+int main(int argc, char **argv)
+{
+	int fd = 0;
+	int key = 0;
+	int *ptr = NULL;
+	int c = 0;
+	int size = 0;
+	char path[256] = "";
+	enum method method = MAX_METHOD;
+	int want_sleep = 0, private = 0;
+	int populate = 0;
+	int write = 0;
+
+	unsigned long i;
+
+
+	if (signal(SIGINT, sig_handler) == SIG_ERR)
+		err(1, "\ncan't catch SIGINT\n");
+
+	/* Parse command-line arguments. */
+	setvbuf(stdout, NULL, _IONBF, 0);
+	self = argv[0];
+
+	while ((c = getopt(argc, argv, "s:p:m:owlr")) != -1) {
+		switch (c) {
+		case 's':
+			size = atoi(optarg);
+			break;
+		case 'p':
+			strncpy(path, optarg, sizeof(path));
+			break;
+		case 'm':
+			if (atoi(optarg) >= MAX_METHOD) {
+				errno = EINVAL;
+				perror("Invalid -m.");
+				exit_usage();
+			}
+			method = atoi(optarg);
+			break;
+		case 'o':
+			populate = 1;
+			break;
+		case 'w':
+			write = 1;
+			break;
+		case 'l':
+			want_sleep = 1;
+			break;
+		case 'r':
+			private = 1;
+			break;
+		default:
+			errno = EINVAL;
+			perror("Invalid arg");
+			exit_usage();
+		}
+	}
+
+	if (strncmp(path, "", sizeof(path)) != 0) {
+		printf("Writing to this path: %s\n", path);
+	} else {
+		errno = EINVAL;
+		perror("path not found");
+		exit_usage();
+	}
+
+	if (size != 0) {
+		printf("Writing this size: %d\n", size);
+	} else {
+		errno = EINVAL;
+		perror("size not found");
+		exit_usage();
+	}
+
+	if (!populate)
+		printf("Not populating.\n");
+	else
+		printf("Populating.\n");
+
+	if (!write)
+		printf("Not writing to memory.\n");
+
+	if (method == MAX_METHOD) {
+		errno = EINVAL;
+		perror("-m Invalid");
+		exit_usage();
+	} else
+		printf("Using method=%d\n", method);
+
+	if (!private)
+		printf("Shared mapping.\n");
+	else
+		printf("Private mapping.\n");
+
+
+	switch (method) {
+	case HUGETLBFS:
+		printf("Allocating using HUGETLBFS.\n");
+		fd = open(path, O_CREAT | O_RDWR, 0777);
+		if (fd == -1)
+			err(1, "Failed to open file.");
+
+		ptr = mmap(NULL, size, PROT_READ | PROT_WRITE,
+			(private ? MAP_PRIVATE : MAP_SHARED) | (populate ?
+				MAP_POPULATE : 0), fd, 0);
+
+		if (ptr == MAP_FAILED) {
+			close(fd);
+			err(1, "Error mapping the file");
+		}
+		break;
+	case MMAP_MAP_HUGETLB:
+		printf("Allocating using MAP_HUGETLB.\n");
+		ptr = mmap(NULL, size,
+		PROT_READ | PROT_WRITE,
+		(private ? (MAP_PRIVATE | MAP_ANONYMOUS) : MAP_SHARED) |
+		MAP_HUGETLB | (populate ?
+			MAP_POPULATE : 0),
+		-1, 0);
+
+		if (ptr == MAP_FAILED)
+			err(1, "mmap");
+
+		printf("Returned address is %p\n", ptr);
+		break;
+	case SHM:
+		printf("Allocating using SHM.\n");
+		shmid = shmget(key, size, SHM_HUGETLB | IPC_CREAT | SHM_R |
+				SHM_W);
+		if (shmid < 0) {
+			shmid = shmget(++key, size, SHM_HUGETLB | IPC_CREAT |
+					SHM_R | SHM_W);
+			if (shmid < 0)
+				err(1, "shmget");
+
+		}
+		printf("shmid: 0x%x, shmget key:%d\n", shmid, key);
+
+		shmaddr = shmat(shmid, NULL, 0);
+		if (shmaddr == (char *)-1) {
+			perror("Shared memory attach failure");
+			shmctl(shmid, IPC_RMID, NULL);
+			exit(2);
+		}
+		printf("shmaddr: %p\n", shmaddr);
+
+		break;
+	default:
+		errno = EINVAL;
+		err(1, "Invalid method.");
+	}
+
+	if (write) {
+		printf("Writing to memory.\n");
+		if (method != SHM) {
+			memset(ptr, 1, size);
+		} else {
+			printf("Starting the writes:\n");
+			for (i = 0; i < size; i++) {
+				shmaddr[i] = (char)(i);
+				if (!(i % (1024 * 1024)))
+					printf(".");
+			}
+			printf("\n");
+
+			printf("Starting the Check...");
+			for (i = 0; i < size; i++)
+				if (shmaddr[i] != (char)i) {
+					printf("\nIndex %lu mismatched\n", i);
+					exit(3);
+				}
+			printf("Done.\n");
+
+
+		}
+	}
+
+	if (want_sleep) {
+		/* Signal to caller that we're done. */
+		printf("DONE\n");
+
+		/* Hold memory until external kill signal is delivered. */
+		while (1)
+			sleep(100);
+	}
+
+	close(fd);
+
+	return 0;
+}
--
2.23.0.187.g17f5b7556c-goog

[PATCH v3 6/6] hugetlb_cgroup: Add hugetlb_cgroup reservation docs

[Mina Almasry]

Add docs for how to use hugetlb_cgroup reservations, and their behavior.

---
 .../admin-guide/cgroup-v1/hugetlb.rst         | 84 ++++++++++++++++---
 1 file changed, 73 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v1/hugetlb.rst b/Documentation/admin-guide/cgroup-v1/hugetlb.rst
index a3902aa253a96..cc6eb859fc722 100644
--- a/Documentation/admin-guide/cgroup-v1/hugetlb.rst
+++ b/Documentation/admin-guide/cgroup-v1/hugetlb.rst
@@ -2,13 +2,6 @@
 HugeTLB Controller
 ==================

-The HugeTLB controller allows to limit the HugeTLB usage per control group and
-enforces the controller limit during page fault. Since HugeTLB doesn't
-support page reclaim, enforcing the limit at page fault time implies that,
-the application will get SIGBUS signal if it tries to access HugeTLB pages
-beyond its limit. This requires the application to know beforehand how much
-HugeTLB pages it would require for its use.
-
 HugeTLB controller can be created by first mounting the cgroup filesystem.

 # mount -t cgroup -o hugetlb none /sys/fs/cgroup
@@ -28,10 +21,14 @@ process (bash) into it.

 Brief summary of control files::

- hugetlb.<hugepagesize>.limit_in_bytes     # set/show limit of "hugepagesize" hugetlb usage
- hugetlb.<hugepagesize>.max_usage_in_bytes # show max "hugepagesize" hugetlb  usage recorded
- hugetlb.<hugepagesize>.usage_in_bytes     # show current usage for "hugepagesize" hugetlb
- hugetlb.<hugepagesize>.failcnt		   # show the number of allocation failure due to HugeTLB limit
+ hugetlb.<hugepagesize>.reservation_limit_in_bytes     # set/show limit of "hugepagesize" hugetlb reservations
+ hugetlb.<hugepagesize>.reservation_max_usage_in_bytes # show max "hugepagesize" hugetlb reservations recorded
+ hugetlb.<hugepagesize>.reservation_usage_in_bytes     # show current reservations for "hugepagesize" hugetlb
+ hugetlb.<hugepagesize>.reservation_failcnt            # show the number of allocation failure due to HugeTLB reservation limit
+ hugetlb.<hugepagesize>.limit_in_bytes                 # set/show limit of "hugepagesize" hugetlb faults
+ hugetlb.<hugepagesize>.max_usage_in_bytes             # show max "hugepagesize" hugetlb  usage recorded
+ hugetlb.<hugepagesize>.usage_in_bytes                 # show current usage for "hugepagesize" hugetlb
+ hugetlb.<hugepagesize>.failcnt                        # show the number of allocation failure due to HugeTLB usage limit

 For a system supporting three hugepage sizes (64k, 32M and 1G), the control
 files include::
@@ -40,11 +37,76 @@ files include::
   hugetlb.1GB.max_usage_in_bytes
   hugetlb.1GB.usage_in_bytes
   hugetlb.1GB.failcnt
+  hugetlb.1GB.reservation_limit_in_bytes
+  hugetlb.1GB.reservation_max_usage_in_bytes
+  hugetlb.1GB.reservation_usage_in_bytes
+  hugetlb.1GB.reservation_failcnt
   hugetlb.64KB.limit_in_bytes
   hugetlb.64KB.max_usage_in_bytes
   hugetlb.64KB.usage_in_bytes
   hugetlb.64KB.failcnt
+  hugetlb.64KB.reservation_limit_in_bytes
+  hugetlb.64KB.reservation_max_usage_in_bytes
+  hugetlb.64KB.reservation_usage_in_bytes
+  hugetlb.64KB.reservation_failcnt
   hugetlb.32MB.limit_in_bytes
   hugetlb.32MB.max_usage_in_bytes
   hugetlb.32MB.usage_in_bytes
   hugetlb.32MB.failcnt
+  hugetlb.32MB.reservation_limit_in_bytes
+  hugetlb.32MB.reservation_max_usage_in_bytes
+  hugetlb.32MB.reservation_usage_in_bytes
+  hugetlb.32MB.reservation_failcnt
+
+
+1. Reservation limits
+
+The HugeTLB controller allows to limit the HugeTLB reservations per control
+group and enforces the controller limit at reservation time. Reservation limits
+are superior to Page fault limits (see section 2), since Reservation limits are
+enforced at reservation time, and never causes the application to get SIGBUS
+signal. Instead, if the application is violating its limits, then it gets an
+error on reservation time, i.e. the mmap or shmget return an error.
+
+
+2. Page fault limits
+
+The HugeTLB controller allows to limit the HugeTLB usage (page fault) per
+control group and enforces the controller limit during page fault. Since HugeTLB
+doesn't support page reclaim, enforcing the limit at page fault time implies
+that, the application will get SIGBUS signal if it tries to access HugeTLB
+pages beyond its limit. This requires the application to know beforehand how
+much HugeTLB pages it would require for its use.
+
+
+3. Caveats with shared memory
+
+a. Charging and uncharging:
+
+For shared hugetlb memory, both hugetlb reservation and usage (page faults) are
+charged to the first task that causes the memory to be reserved or faulted,
+and all subsequent uses of this reserved or faulted memory is done without
+charging.
+
+Shared hugetlb memory is only uncharged when it is unreseved or deallocated.
+This is usually when the hugetlbfs file is deleted, and not when the task that
+caused the reservation or fault has exited.
+
+b. Interaction between reservation limit and fault limit.
+
+Generally, it's not recommended to set both of the reservation limit and fault
+limit in a cgroup. For private memory, the fault usage cannot exceed the
+reservation usage, so if you set both, one of those limits will be useless.
+
+For shared memory, a cgroup's fault usage may be greater than its reservation
+usage, so some care needs to be taken. Consider this example:
+
+- Task A reserves 4 pages in a shared hugetlbfs file. Cgroup A will get
+  4 reservations charged to it and no faults charged to it.
+- Task B reserves and faults the same 4 pages as Task A. Cgroup B will get no
+  reservation charge, but will get charged 4 faulted pages. If Cgroup B's limit
+  is less than 4, then Task B will get a SIGBUS.
+
+For the above scenario, it's not recommended for the userspace to set both
+reservation limits and fault limits, but it is still allowed to in case it sees
+some use for it.
--
2.23.0.187.g17f5b7556c-goog

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Michal Hocko]

On Mon 26-08-19 16:32:34, Mina Almasry wrote:
>  mm/hugetlb.c                                  | 493 ++++++++++++------
>  mm/hugetlb_cgroup.c                           | 187 +++++--

This is a lot of changes to an already subtle code which hugetlb
reservations undoubly are. Moreover cgroupv1 is feature frozen and I am
not aware of any plans to port the controller to v2. That all doesn't
sound in favor of this change. Mike is the maintainer of the hugetlb
code so I will defer to him to make a decision but I wouldn't recommend
that.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mina Almasry]

On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
> >  mm/hugetlb.c                                  | 493 ++++++++++++------
> >  mm/hugetlb_cgroup.c                           | 187 +++++--
>
> This is a lot of changes to an already subtle code which hugetlb
> reservations undoubly are.

For what it's worth, I think this patch series is a net decrease in
the complexity of the reservation code, especially the region_*
functions, which is where a lot of the complexity lies. I removed the
race between region_del and region_{add|chg}, refactored the main
logic into smaller code, moved common code to helpers and deleted the
duplicates, and finally added lots of comments to the hard to
understand pieces. I hope that when folks review the changes they will
see that! :)

> Moreover cgroupv1 is feature frozen and I am
> not aware of any plans to port the controller to v2.

Also for what it's worth, if porting the controller to v2 is a
requisite to take this, I'm happy to do that. As far as I understand
there is no reason hugetlb_cgroups shouldn't be in cgroups v2, and we
see value in them.

> That all doesn't
> sound in favor of this change. Mike is the maintainer of the hugetlb
> code so I will defer to him to make a decision but I wouldn't recommend
> that.
> --
> Michal Hocko
> SUSE Labs

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Shakeel Butt]

On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
> >  mm/hugetlb.c                                  | 493 ++++++++++++------
> >  mm/hugetlb_cgroup.c                           | 187 +++++--
>
> This is a lot of changes to an already subtle code which hugetlb
> reservations undoubly are. Moreover cgroupv1 is feature frozen and I am
> not aware of any plans to port the controller to v2. That all doesn't
> sound in favor of this change.

Actually "no plan to port the controller to v2" makes the case strong
for these changes (and other new features) to be done in v1. If there
is an alternative solution in v2 then I can understand the push-back
on changes in v1 but that is not the case here.

Shakeel

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Michal Hocko]

[Cc cgroups maintainers]

On Wed 28-08-19 10:58:00, Mina Almasry wrote:
> On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
> >
> > On Mon 26-08-19 16:32:34, Mina Almasry wrote:
> > >  mm/hugetlb.c                                  | 493 ++++++++++++------
> > >  mm/hugetlb_cgroup.c                           | 187 +++++--
> >
> > This is a lot of changes to an already subtle code which hugetlb
> > reservations undoubly are.
> 
> For what it's worth, I think this patch series is a net decrease in
> the complexity of the reservation code, especially the region_*
> functions, which is where a lot of the complexity lies. I removed the
> race between region_del and region_{add|chg}, refactored the main
> logic into smaller code, moved common code to helpers and deleted the
> duplicates, and finally added lots of comments to the hard to
> understand pieces. I hope that when folks review the changes they will
> see that! :)

Post those improvements as standalone patches and sell them as
improvements. We can talk about the net additional complexity of the
controller much easier then.

> > Moreover cgroupv1 is feature frozen and I am
> > not aware of any plans to port the controller to v2.
> 
> Also for what it's worth, if porting the controller to v2 is a
> requisite to take this, I'm happy to do that. As far as I understand
> there is no reason hugetlb_cgroups shouldn't be in cgroups v2, and we
> see value in them.

Talk to cgroups maintainers why the hugegetlb controller hasn't been
enabled in v2. All I am saing is that v1 only features are really a hard
sell. Even without adding a lot of code to hugetlb which is quite
complex on its own.
-- 
Michal Hocko
SUSE Labs

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mike Kravetz]

On 8/29/19 12:18 AM, Michal Hocko wrote:
> [Cc cgroups maintainers]
> 
> On Wed 28-08-19 10:58:00, Mina Almasry wrote:
>> On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
>>>
>>> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
>>>>  mm/hugetlb.c                                  | 493 ++++++++++++------
>>>>  mm/hugetlb_cgroup.c                           | 187 +++++--
>>>
>>> This is a lot of changes to an already subtle code which hugetlb
>>> reservations undoubly are.
>>
>> For what it's worth, I think this patch series is a net decrease in
>> the complexity of the reservation code, especially the region_*
>> functions, which is where a lot of the complexity lies. I removed the
>> race between region_del and region_{add|chg}, refactored the main
>> logic into smaller code, moved common code to helpers and deleted the
>> duplicates, and finally added lots of comments to the hard to
>> understand pieces. I hope that when folks review the changes they will
>> see that! :)
> 
> Post those improvements as standalone patches and sell them as
> improvements. We can talk about the net additional complexity of the
> controller much easier then.

All such changes appear to be in patch 4 of this series.  The commit message
says "region_add() and region_chg() are heavily refactored to in this commit
to make the code easier to understand and remove duplication.".  However, the
modifications were also added to accommodate the new cgroup reservation
accounting.  I think it would be helpful to explain why the existing code does
not work with the new accounting.  For example, one change is because
"existing code coalesces resv_map entries for shared mappings.  new cgroup
accounting requires that resv_map entries be kept separate for proper
uncharging."

I am starting to review the changes, but it would help if there was a high
level description.  I also like Michal's idea of calling out the region_*
changes separately.  If not a standalone patch, at least the first patch of
the series.  This new code will be exercised even if cgroup reservation
accounting not enabled, so it is very important than no subtle regressions
be introduced.

-- 
Mike Kravetz

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mike Kravetz]

On 9/3/19 10:57 AM, Mike Kravetz wrote:
> On 8/29/19 12:18 AM, Michal Hocko wrote:
>> [Cc cgroups maintainers]
>>
>> On Wed 28-08-19 10:58:00, Mina Almasry wrote:
>>> On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
>>>>
>>>> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
>>>>>  mm/hugetlb.c                                  | 493 ++++++++++++------
>>>>>  mm/hugetlb_cgroup.c                           | 187 +++++--
>>>>
>>>> This is a lot of changes to an already subtle code which hugetlb
>>>> reservations undoubly are.
>>>
>>> For what it's worth, I think this patch series is a net decrease in
>>> the complexity of the reservation code, especially the region_*
>>> functions, which is where a lot of the complexity lies. I removed the
>>> race between region_del and region_{add|chg}, refactored the main
>>> logic into smaller code, moved common code to helpers and deleted the
>>> duplicates, and finally added lots of comments to the hard to
>>> understand pieces. I hope that when folks review the changes they will
>>> see that! :)
>>
>> Post those improvements as standalone patches and sell them as
>> improvements. We can talk about the net additional complexity of the
>> controller much easier then.
> 
> All such changes appear to be in patch 4 of this series.  The commit message
> says "region_add() and region_chg() are heavily refactored to in this commit
> to make the code easier to understand and remove duplication.".  However, the
> modifications were also added to accommodate the new cgroup reservation
> accounting.  I think it would be helpful to explain why the existing code does
> not work with the new accounting.  For example, one change is because
> "existing code coalesces resv_map entries for shared mappings.  new cgroup
> accounting requires that resv_map entries be kept separate for proper
> uncharging."
> 
> I am starting to review the changes, but it would help if there was a high
> level description.  I also like Michal's idea of calling out the region_*
> changes separately.  If not a standalone patch, at least the first patch of
> the series.  This new code will be exercised even if cgroup reservation
> accounting not enabled, so it is very important than no subtle regressions
> be introduced.

While looking at the region_* changes, I started thinking about this no
coalesce change for shared mappings which I think is necessary.  Am I
mistaken, or is this a requirement?

If it is a requirement, then think about some of the possible scenarios
such as:
- There is a hugetlbfs file of size 10 huge pages.
- Task A has reservations for pages at offset 1 3 5 7 and 9
- Task B then mmaps the entire file which should result in reservations
  at 0 2 4 6 and 8.
- region_chg will return 5, but will also need to allocate 5 resv_map
  entries for the subsequent region_add which can not fail.  Correct?
  The code does not appear to handle this.

BTW, this series will BUG when running libhugetlbfs test suite.  It will
hit this in resv_map_release().

	VM_BUG_ON(resv_map->adds_in_progress);

-- 
Mike Kravetz

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mina Almasry]

On Tue, Sep 3, 2019 at 10:58 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 8/29/19 12:18 AM, Michal Hocko wrote:
> > [Cc cgroups maintainers]
> >
> > On Wed 28-08-19 10:58:00, Mina Almasry wrote:
> >> On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
> >>>
> >>> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
> >>>>  mm/hugetlb.c                                  | 493 ++++++++++++------
> >>>>  mm/hugetlb_cgroup.c                           | 187 +++++--
> >>>
> >>> This is a lot of changes to an already subtle code which hugetlb
> >>> reservations undoubly are.
> >>
> >> For what it's worth, I think this patch series is a net decrease in
> >> the complexity of the reservation code, especially the region_*
> >> functions, which is where a lot of the complexity lies. I removed the
> >> race between region_del and region_{add|chg}, refactored the main
> >> logic into smaller code, moved common code to helpers and deleted the
> >> duplicates, and finally added lots of comments to the hard to
> >> understand pieces. I hope that when folks review the changes they will
> >> see that! :)
> >
> > Post those improvements as standalone patches and sell them as
> > improvements. We can talk about the net additional complexity of the
> > controller much easier then.
>
> All such changes appear to be in patch 4 of this series.  The commit message
> says "region_add() and region_chg() are heavily refactored to in this commit
> to make the code easier to understand and remove duplication.".  However, the
> modifications were also added to accommodate the new cgroup reservation
> accounting.  I think it would be helpful to explain why the existing code does
> not work with the new accounting.  For example, one change is because
> "existing code coalesces resv_map entries for shared mappings.  new cgroup
> accounting requires that resv_map entries be kept separate for proper
> uncharging."
>
> I am starting to review the changes, but it would help if there was a high
> level description.  I also like Michal's idea of calling out the region_*
> changes separately.  If not a standalone patch, at least the first patch of
> the series.  This new code will be exercised even if cgroup reservation
> accounting not enabled, so it is very important than no subtle regressions
> be introduced.
>

Yep, seems I'm not calling out these changes as clearly as I should.
I'll look into breaking them into separate patches. I'll probably put
them as a separate patch or right behind current patchset 4, since
they are really done to make removing the coalescing a bit easier. Let
me look into that.

> --
> Mike Kravetz

Re: [PATCH v3 0/6] hugetlb_cgroup: Add hugetlb_cgroup reservation limits

[Mina Almasry]

On Tue, Sep 3, 2019 at 4:46 PM Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 9/3/19 10:57 AM, Mike Kravetz wrote:
> > On 8/29/19 12:18 AM, Michal Hocko wrote:
> >> [Cc cgroups maintainers]
> >>
> >> On Wed 28-08-19 10:58:00, Mina Almasry wrote:
> >>> On Wed, Aug 28, 2019 at 4:23 AM Michal Hocko <mhocko@kernel.org> wrote:
> >>>>
> >>>> On Mon 26-08-19 16:32:34, Mina Almasry wrote:
> >>>>>  mm/hugetlb.c                                  | 493 ++++++++++++------
> >>>>>  mm/hugetlb_cgroup.c                           | 187 +++++--
> >>>>
> >>>> This is a lot of changes to an already subtle code which hugetlb
> >>>> reservations undoubly are.
> >>>
> >>> For what it's worth, I think this patch series is a net decrease in
> >>> the complexity of the reservation code, especially the region_*
> >>> functions, which is where a lot of the complexity lies. I removed the
> >>> race between region_del and region_{add|chg}, refactored the main
> >>> logic into smaller code, moved common code to helpers and deleted the
> >>> duplicates, and finally added lots of comments to the hard to
> >>> understand pieces. I hope that when folks review the changes they will
> >>> see that! :)
> >>
> >> Post those improvements as standalone patches and sell them as
> >> improvements. We can talk about the net additional complexity of the
> >> controller much easier then.
> >
> > All such changes appear to be in patch 4 of this series.  The commit message
> > says "region_add() and region_chg() are heavily refactored to in this commit
> > to make the code easier to understand and remove duplication.".  However, the
> > modifications were also added to accommodate the new cgroup reservation
> > accounting.  I think it would be helpful to explain why the existing code does
> > not work with the new accounting.  For example, one change is because
> > "existing code coalesces resv_map entries for shared mappings.  new cgroup
> > accounting requires that resv_map entries be kept separate for proper
> > uncharging."
> >
> > I am starting to review the changes, but it would help if there was a high
> > level description.  I also like Michal's idea of calling out the region_*
> > changes separately.  If not a standalone patch, at least the first patch of
> > the series.  This new code will be exercised even if cgroup reservation
> > accounting not enabled, so it is very important than no subtle regressions
> > be introduced.
>
> While looking at the region_* changes, I started thinking about this no
> coalesce change for shared mappings which I think is necessary.  Am I
> mistaken, or is this a requirement?
>

No coalesce is a requirement, yes. The idea is that task A can reseve
range [0-1], and task B can reserve range [1-2]. We want the code to
put in 2 regions:

1. [0-1], with cgroup information that points to task A's cgroup.
2. [1-2], with cgroup information that points to task B's cgroup.

If coalescing is happening, then you end up with one region [0-2] with
cgroup information for one of those cgroups, and someone gets
uncharged wrong when the reservation is freed.

Technically we can still coalesce if the cgroup information is the
same and I can do that, but the region_* code becomes more
complicated, and you mentioned on an earlier patchset that you were
concerned with how complicated the region_* functions are as is.

> If it is a requirement, then think about some of the possible scenarios
> such as:
> - There is a hugetlbfs file of size 10 huge pages.
> - Task A has reservations for pages at offset 1 3 5 7 and 9
> - Task B then mmaps the entire file which should result in reservations
>   at 0 2 4 6 and 8.
> - region_chg will return 5, but will also need to allocate 5 resv_map
>   entries for the subsequent region_add which can not fail.  Correct?
>   The code does not appear to handle this.
>

I thought the code did handle this. region_chg calls
allocate_enough_cache_for_range_and_lock(), which in this scenario
will put 5 entries in resv_map->region_cache. region_add will use
these 5 region_cache entries to do its business.

I'll add a test in my suite to test this case to make sure.

> BTW, this series will BUG when running libhugetlbfs test suite.  It will
> hit this in resv_map_release().
>
>         VM_BUG_ON(resv_map->adds_in_progress);
>

Sorry about that, I've been having trouble running the libhugetlbfs
tests, but I'm still on it. I'll get to the bottom of this by next
patch series.

> --
> Mike Kravetz