The patch titled
Subject: mm: zsmalloc: remove object mapping APIs and per-CPU map areas
has been added to the -mm mm-unstable branch. Its filename is
mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
Subject: mm: zsmalloc: remove object mapping APIs and per-CPU map areas
Date: Wed, 5 Mar 2025 06:11:32 +0000
zs_map_object() and zs_unmap_object() are no longer used, remove them.
Since these are the only users of per-CPU mapping_areas, remove them and
the associated CPU hotplug callbacks too.
Link: https://lkml.kernel.org/r/20250305061134.4105762-5-yosry.ahmed@xxxxxxxxx
Signed-off-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
Acked-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Nhat Pham <nphamcs@xxxxxxxxx>
Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/cpuhotplug.h | 1
include/linux/zsmalloc.h | 21 ---
mm/zsmalloc.c | 226 -----------------------------------
3 files changed, 1 insertion(+), 247 deletions(-)
--- a/include/linux/cpuhotplug.h~mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas
+++ a/include/linux/cpuhotplug.h
@@ -116,7 +116,6 @@ enum cpuhp_state {
CPUHP_NET_IUCV_PREPARE,
CPUHP_ARM_BL_PREPARE,
CPUHP_TRACE_RB_PREPARE,
- CPUHP_MM_ZS_PREPARE,
CPUHP_MM_ZSWP_POOL_PREPARE,
CPUHP_KVM_PPC_BOOK3S_PREPARE,
CPUHP_ZCOMP_PREPARE,
--- a/include/linux/zsmalloc.h~mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas
+++ a/include/linux/zsmalloc.h
@@ -16,23 +16,6 @@
#include <linux/types.h>
-/*
- * zsmalloc mapping modes
- *
- * NOTE: These only make a difference when a mapped object spans pages.
- */
-enum zs_mapmode {
- ZS_MM_RW, /* normal read-write mapping */
- ZS_MM_RO, /* read-only (no copy-out at unmap time) */
- ZS_MM_WO /* write-only (no copy-in at map time) */
- /*
- * NOTE: ZS_MM_WO should only be used for initializing new
- * (uninitialized) allocations. Partial writes to already
- * initialized allocations should use ZS_MM_RW to preserve the
- * existing data.
- */
-};
-
struct zs_pool_stats {
/* How many pages were migrated (freed) */
atomic_long_t pages_compacted;
@@ -48,10 +31,6 @@ void zs_free(struct zs_pool *pool, unsig
size_t zs_huge_class_size(struct zs_pool *pool);
-void *zs_map_object(struct zs_pool *pool, unsigned long handle,
- enum zs_mapmode mm);
-void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
-
unsigned long zs_get_total_pages(struct zs_pool *pool);
unsigned long zs_compact(struct zs_pool *pool);
--- a/mm/zsmalloc.c~mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas
+++ a/mm/zsmalloc.c
@@ -281,13 +281,6 @@ struct zspage {
struct zspage_lock zsl;
};
-struct mapping_area {
- local_lock_t lock;
- char *vm_buf; /* copy buffer for objects that span pages */
- char *vm_addr; /* address of kmap_local_page()'ed pages */
- enum zs_mapmode vm_mm; /* mapping mode */
-};
-
static void zspage_lock_init(struct zspage *zspage)
{
static struct lock_class_key __key;
@@ -522,11 +515,6 @@ static struct zpool_driver zs_zpool_driv
MODULE_ALIAS("zpool-zsmalloc");
#endif /* CONFIG_ZPOOL */
-/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
-static DEFINE_PER_CPU(struct mapping_area, zs_map_area) = {
- .lock = INIT_LOCAL_LOCK(lock),
-};
-
static inline bool __maybe_unused is_first_zpdesc(struct zpdesc *zpdesc)
{
return PagePrivate(zpdesc_page(zpdesc));
@@ -1111,93 +1099,6 @@ static struct zspage *find_get_zspage(st
return zspage;
}
-static inline int __zs_cpu_up(struct mapping_area *area)
-{
- /*
- * Make sure we don't leak memory if a cpu UP notification
- * and zs_init() race and both call zs_cpu_up() on the same cpu
- */
- if (area->vm_buf)
- return 0;
- area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
- if (!area->vm_buf)
- return -ENOMEM;
- return 0;
-}
-
-static inline void __zs_cpu_down(struct mapping_area *area)
-{
- kfree(area->vm_buf);
- area->vm_buf = NULL;
-}
-
-static void *__zs_map_object(struct mapping_area *area,
- struct zpdesc *zpdescs[2], int off, int size)
-{
- size_t sizes[2];
- char *buf = area->vm_buf;
-
- /* disable page faults to match kmap_local_page() return conditions */
- pagefault_disable();
-
- /* no read fastpath */
- if (area->vm_mm == ZS_MM_WO)
- goto out;
-
- sizes[0] = PAGE_SIZE - off;
- sizes[1] = size - sizes[0];
-
- /* copy object to per-cpu buffer */
- memcpy_from_page(buf, zpdesc_page(zpdescs[0]), off, sizes[0]);
- memcpy_from_page(buf + sizes[0], zpdesc_page(zpdescs[1]), 0, sizes[1]);
-out:
- return area->vm_buf;
-}
-
-static void __zs_unmap_object(struct mapping_area *area,
- struct zpdesc *zpdescs[2], int off, int size)
-{
- size_t sizes[2];
- char *buf;
-
- /* no write fastpath */
- if (area->vm_mm == ZS_MM_RO)
- goto out;
-
- buf = area->vm_buf;
- buf = buf + ZS_HANDLE_SIZE;
- size -= ZS_HANDLE_SIZE;
- off += ZS_HANDLE_SIZE;
-
- sizes[0] = PAGE_SIZE - off;
- sizes[1] = size - sizes[0];
-
- /* copy per-cpu buffer to object */
- memcpy_to_page(zpdesc_page(zpdescs[0]), off, buf, sizes[0]);
- memcpy_to_page(zpdesc_page(zpdescs[1]), 0, buf + sizes[0], sizes[1]);
-
-out:
- /* enable page faults to match kunmap_local() return conditions */
- pagefault_enable();
-}
-
-static int zs_cpu_prepare(unsigned int cpu)
-{
- struct mapping_area *area;
-
- area = &per_cpu(zs_map_area, cpu);
- return __zs_cpu_up(area);
-}
-
-static int zs_cpu_dead(unsigned int cpu)
-{
- struct mapping_area *area;
-
- area = &per_cpu(zs_map_area, cpu);
- __zs_cpu_down(area);
- return 0;
-}
-
static bool can_merge(struct size_class *prev, int pages_per_zspage,
int objs_per_zspage)
{
@@ -1245,117 +1146,6 @@ unsigned long zs_get_total_pages(struct
}
EXPORT_SYMBOL_GPL(zs_get_total_pages);
-/**
- * zs_map_object - get address of allocated object from handle.
- * @pool: pool from which the object was allocated
- * @handle: handle returned from zs_malloc
- * @mm: mapping mode to use
- *
- * Before using an object allocated from zs_malloc, it must be mapped using
- * this function. When done with the object, it must be unmapped using
- * zs_unmap_object.
- *
- * Only one object can be mapped per cpu at a time. There is no protection
- * against nested mappings.
- *
- * This function returns with preemption and page faults disabled.
- */
-void *zs_map_object(struct zs_pool *pool, unsigned long handle,
- enum zs_mapmode mm)
-{
- struct zspage *zspage;
- struct zpdesc *zpdesc;
- unsigned long obj, off;
- unsigned int obj_idx;
-
- struct size_class *class;
- struct mapping_area *area;
- struct zpdesc *zpdescs[2];
- void *ret;
-
- /*
- * Because we use per-cpu mapping areas shared among the
- * pools/users, we can't allow mapping in interrupt context
- * because it can corrupt another users mappings.
- */
- BUG_ON(in_interrupt());
-
- /* It guarantees it can get zspage from handle safely */
- read_lock(&pool->lock);
- obj = handle_to_obj(handle);
- obj_to_location(obj, &zpdesc, &obj_idx);
- zspage = get_zspage(zpdesc);
-
- /*
- * migration cannot move any zpages in this zspage. Here, class->lock
- * is too heavy since callers would take some time until they calls
- * zs_unmap_object API so delegate the locking from class to zspage
- * which is smaller granularity.
- */
- zspage_read_lock(zspage);
- read_unlock(&pool->lock);
-
- class = zspage_class(pool, zspage);
- off = offset_in_page(class->size * obj_idx);
-
- local_lock(&zs_map_area.lock);
- area = this_cpu_ptr(&zs_map_area);
- area->vm_mm = mm;
- if (off + class->size <= PAGE_SIZE) {
- /* this object is contained entirely within a page */
- area->vm_addr = kmap_local_zpdesc(zpdesc);
- ret = area->vm_addr + off;
- goto out;
- }
-
- /* this object spans two pages */
- zpdescs[0] = zpdesc;
- zpdescs[1] = get_next_zpdesc(zpdesc);
- BUG_ON(!zpdescs[1]);
-
- ret = __zs_map_object(area, zpdescs, off, class->size);
-out:
- if (likely(!ZsHugePage(zspage)))
- ret += ZS_HANDLE_SIZE;
-
- return ret;
-}
-EXPORT_SYMBOL_GPL(zs_map_object);
-
-void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
-{
- struct zspage *zspage;
- struct zpdesc *zpdesc;
- unsigned long obj, off;
- unsigned int obj_idx;
-
- struct size_class *class;
- struct mapping_area *area;
-
- obj = handle_to_obj(handle);
- obj_to_location(obj, &zpdesc, &obj_idx);
- zspage = get_zspage(zpdesc);
- class = zspage_class(pool, zspage);
- off = offset_in_page(class->size * obj_idx);
-
- area = this_cpu_ptr(&zs_map_area);
- if (off + class->size <= PAGE_SIZE)
- kunmap_local(area->vm_addr);
- else {
- struct zpdesc *zpdescs[2];
-
- zpdescs[0] = zpdesc;
- zpdescs[1] = get_next_zpdesc(zpdesc);
- BUG_ON(!zpdescs[1]);
-
- __zs_unmap_object(area, zpdescs, off, class->size);
- }
- local_unlock(&zs_map_area.lock);
-
- zspage_read_unlock(zspage);
-}
-EXPORT_SYMBOL_GPL(zs_unmap_object);
-
void *zs_obj_read_begin(struct zs_pool *pool, unsigned long handle,
void *local_copy)
{
@@ -1975,7 +1765,7 @@ static int zs_page_migrate(struct page *
* the class lock protects zpage alloc/free in the zspage.
*/
spin_lock(&class->lock);
- /* the zspage write_lock protects zpage access via zs_map_object */
+ /* the zspage write_lock protects zpage access via zs_obj_read/write() */
if (!zspage_write_trylock(zspage)) {
spin_unlock(&class->lock);
write_unlock(&pool->lock);
@@ -2459,23 +2249,11 @@ EXPORT_SYMBOL_GPL(zs_destroy_pool);
static int __init zs_init(void)
{
- int ret;
-
- ret = cpuhp_setup_state(CPUHP_MM_ZS_PREPARE, "mm/zsmalloc:prepare",
- zs_cpu_prepare, zs_cpu_dead);
- if (ret)
- goto out;
-
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
-
zs_stat_init();
-
return 0;
-
-out:
- return ret;
}
static void __exit zs_exit(void)
@@ -2483,8 +2261,6 @@ static void __exit zs_exit(void)
#ifdef CONFIG_ZPOOL
zpool_unregister_driver(&zs_zpool_driver);
#endif
- cpuhp_remove_state(CPUHP_MM_ZS_PREPARE);
-
zs_stat_exit();
}
_
Patches currently in -mm which might be from yosry.ahmed@xxxxxxxxx are
mm-z3fold-remove-z3fold.patch
mm-zbud-remove-zbud.patch
mm-zpool-add-interfaces-for-object-read-write-apis.patch
mm-zswap-use-object-read-write-apis-instead-of-object-mapping-apis.patch
mm-zpool-remove-object-mapping-apis.patch
mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas.patch
mm-zsmalloc-remove-object-mapping-apis-and-per-cpu-map-areas-fix.patch
mm-zpool-remove-zpool_malloc_support_movable.patch
