[PATCH v3 4/5] alloc_tag: introduce pgalloc_tag_ref to abstract page tag references

Suren Baghdasaryan
2024-10-14T20:36:59Z

To simplify later changes to page tag references, introduce new
pgalloc_tag_ref and pgtag_ref_handle types. This allows easy
replacement of page_ext as a storage of page allocation tags.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
include/linux/mm.h | 25 +++++----
include/linux/pgalloc_tag.h | 108 ++++++++++++++++++++++++------------
lib/alloc_tag.c | 3 +-
3 files changed, 88 insertions(+), 48 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5cd22303fbc0..8efb4a6a1a70 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4180,37 +4180,38 @@ static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new
return;

for (i = nr_pages; i < (1 << old_order); i += nr_pages) {
- union codetag_ref *ref = get_page_tag_ref(folio_page(folio, i));
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;

- if (ref) {
+ if (get_page_tag_ref(folio_page(folio, i), &ref, &handle)) {
/* Set new reference to point to the original tag */
- alloc_tag_ref_set(ref, tag);
- put_page_tag_ref(ref);
+ alloc_tag_ref_set(&ref, tag);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
}
}
}

static inline void pgalloc_tag_copy(struct folio *new, struct folio *old)
{
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;
struct alloc_tag *tag;
- union codetag_ref *ref;

tag = pgalloc_tag_get(&old->page);
if (!tag)
return;

- ref = get_page_tag_ref(&new->page);
- if (!ref)
+ if (!get_page_tag_ref(&new->page, &ref, &handle))
return;

/* Clear the old ref to the original allocation tag. */
clear_page_tag_ref(&old->page);
/* Decrement the counters of the tag on get_new_folio. */
- alloc_tag_sub(ref, folio_nr_pages(new));
-
- __alloc_tag_ref_set(ref, tag);
-
- put_page_tag_ref(ref);
+ alloc_tag_sub(&ref, folio_nr_pages(new));
+ __alloc_tag_ref_set(&ref, tag);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
}
#else /* !CONFIG_MEM_ALLOC_PROFILING */
static inline void pgalloc_tag_split(struct folio *folio, int old_order, int new_order)
diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h
index 59a3deb792a8..bc65710ee1f9 100644
--- a/include/linux/pgalloc_tag.h
+++ b/include/linux/pgalloc_tag.h
@@ -9,48 +9,83 @@

#ifdef CONFIG_MEM_ALLOC_PROFILING

+typedef union codetag_ref pgalloc_tag_ref;
+
+static inline void read_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref)
+{
+ ref->ct = pgref->ct;
+}
+
+static inline void write_pgref(pgalloc_tag_ref *pgref, union codetag_ref *ref)
+{
+ pgref->ct = ref->ct;
+}
+
+union pgtag_ref_handle {
+ pgalloc_tag_ref *pgref; /* reference in page extension */
+};
+
#include <linux/page_ext.h>

extern struct page_ext_operations page_alloc_tagging_ops;

-static inline union codetag_ref *codetag_ref_from_page_ext(struct page_ext *page_ext)
+static inline pgalloc_tag_ref *pgref_from_page_ext(struct page_ext *page_ext)
{
- return (union codetag_ref *)page_ext_data(page_ext, &page_alloc_tagging_ops);
+ return (pgalloc_tag_ref *)page_ext_data(page_ext, &page_alloc_tagging_ops);
}

-static inline struct page_ext *page_ext_from_codetag_ref(union codetag_ref *ref)
+static inline struct page_ext *page_ext_from_pgref(pgalloc_tag_ref *pgref)
{
- return (void *)ref - page_alloc_tagging_ops.offset;
+ return (void *)pgref - page_alloc_tagging_ops.offset;
}

/* Should be called only if mem_alloc_profiling_enabled() */
-static inline union codetag_ref *get_page_tag_ref(struct page *page)
+static inline bool get_page_tag_ref(struct page *page, union codetag_ref *ref,
+ union pgtag_ref_handle *handle)
{
- if (page) {
- struct page_ext *page_ext = page_ext_get(page);
+ struct page_ext *page_ext;
+ pgalloc_tag_ref *pgref;

- if (page_ext)
- return codetag_ref_from_page_ext(page_ext);
- }
- return NULL;
+ if (!page)
+ return false;
+
+ page_ext = page_ext_get(page);
+ if (!page_ext)
+ return false;
+
+ pgref = pgref_from_page_ext(page_ext);
+ read_pgref(pgref, ref);
+ handle->pgref = pgref;
+ return true;
+}
+
+static inline void put_page_tag_ref(union pgtag_ref_handle handle)
+{
+ if (WARN_ON(!handle.pgref))
+ return;
+
+ page_ext_put(page_ext_from_pgref(handle.pgref));
}

-static inline void put_page_tag_ref(union codetag_ref *ref)
+static inline void update_page_tag_ref(union pgtag_ref_handle handle,
+ union codetag_ref *ref)
{
- if (WARN_ON(!ref))
+ if (WARN_ON(!handle.pgref || !ref))
return;

- page_ext_put(page_ext_from_codetag_ref(ref));
+ write_pgref(handle.pgref, ref);
}

static inline void clear_page_tag_ref(struct page *page)
{
if (mem_alloc_profiling_enabled()) {
- union codetag_ref *ref = get_page_tag_ref(page);
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;

- if (ref) {
- set_codetag_empty(ref);
- put_page_tag_ref(ref);
+ if (get_page_tag_ref(page, &ref, &handle)) {
+ set_codetag_empty(&ref);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
}
}
}
@@ -59,11 +94,13 @@ static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
unsigned int nr)
{
if (mem_alloc_profiling_enabled()) {
- union codetag_ref *ref = get_page_tag_ref(page);
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;

- if (ref) {
- alloc_tag_add(ref, task->alloc_tag, PAGE_SIZE * nr);
- put_page_tag_ref(ref);
+ if (get_page_tag_ref(page, &ref, &handle)) {
+ alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZE * nr);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
}
}
}
@@ -71,11 +108,13 @@ static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
static inline void pgalloc_tag_sub(struct page *page, unsigned int nr)
{
if (mem_alloc_profiling_enabled()) {
- union codetag_ref *ref = get_page_tag_ref(page);
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;

- if (ref) {
- alloc_tag_sub(ref, PAGE_SIZE * nr);
- put_page_tag_ref(ref);
+ if (get_page_tag_ref(page, &ref, &handle)) {
+ alloc_tag_sub(&ref, PAGE_SIZE * nr);
+ update_page_tag_ref(handle, &ref);
+ put_page_tag_ref(handle);
}
}
}
@@ -85,13 +124,14 @@ static inline struct alloc_tag *pgalloc_tag_get(struct page *page)
struct alloc_tag *tag = NULL;

if (mem_alloc_profiling_enabled()) {
- union codetag_ref *ref = get_page_tag_ref(page);
-
- alloc_tag_sub_check(ref);
- if (ref) {
- if (ref->ct)
- tag = ct_to_alloc_tag(ref->ct);
- put_page_tag_ref(ref);
+ union pgtag_ref_handle handle;
+ union codetag_ref ref;
+
+ if (get_page_tag_ref(page, &ref, &handle)) {
+ alloc_tag_sub_check(&ref);
+ if (ref.ct)
+ tag = ct_to_alloc_tag(ref.ct);
+ put_page_tag_ref(handle);
}
}

@@ -106,8 +146,6 @@ static inline void pgalloc_tag_sub_pages(struct alloc_tag *tag, unsigned int nr)

#else /* CONFIG_MEM_ALLOC_PROFILING */

-static inline union codetag_ref *get_page_tag_ref(struct page *page) { return NULL; }
-static inline void put_page_tag_ref(union codetag_ref *ref) {}
static inline void clear_page_tag_ref(struct page *page) {}
static inline void pgalloc_tag_add(struct page *page, struct task_struct *task,
unsigned int nr) {}
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 648f32d52b8d..2ef762acc203 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -5,6 +5,7 @@
#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/page_ext.h>
+#include <linux/pgalloc_tag.h>
#include <linux/proc_fs.h>
#include <linux/seq_buf.h>
#include <linux/seq_file.h>
@@ -474,7 +475,7 @@ static __init void init_page_alloc_tagging(void)
}

struct page_ext_operations page_alloc_tagging_ops = {
- .size = sizeof(union codetag_ref),
+ .size = sizeof(pgalloc_tag_ref),
.need = need_page_alloc_tagging,
.init = init_page_alloc_tagging,
};
--
2.47.0.rc1.288.g06298d1525-goog