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Subject[patch v2 ] mm/zs_malloc: Fix bit spinlock replacement
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Do not alter HANDLE_SIZE, memory corruption ensues. The handle is
a pointer, allocate space for the struct it points to and align it
ZS_ALIGN. Also, when accessing the struct, mask HANDLE_PIN_BIT.

v2: mutex is only needed for PREEMPT_RT_FULL, with PREEMPT_RT_RTB,
preemption is disabled when we take it...

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
---
mm/zsmalloc.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)

--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -71,18 +71,20 @@
#define ZS_MAX_ZSPAGE_ORDER 2
#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)

-#ifdef CONFIG_PREEMPT_RT_BASE
+#define ZS_HANDLE_SIZE (sizeof(unsigned long))
+
+#ifdef CONFIG_PREEMPT_RT_FULL

struct zsmalloc_handle {
unsigned long addr;
struct mutex lock;
};

-#define ZS_HANDLE_SIZE (sizeof(struct zsmalloc_handle))
+#define ZS_HANDLE_ALLOC_SIZE (sizeof(struct zsmalloc_handle))

#else

-#define ZS_HANDLE_SIZE (sizeof(unsigned long))
+#define ZS_HANDLE_ALLOC_SIZE ZS_HANDLE_SIZE
#endif

/*
@@ -339,8 +341,9 @@ static void SetZsPageMovable(struct zs_p

static int create_cache(struct zs_pool *pool)
{
- pool->handle_cachep = kmem_cache_create("zs_handle", ZS_HANDLE_SIZE,
- 0, 0, NULL);
+ pool->handle_cachep = kmem_cache_create("zs_handle",
+ ZS_HANDLE_ALLOC_SIZE,
+ ZS_ALIGN, 0, NULL);
if (!pool->handle_cachep)
return 1;

@@ -367,7 +370,7 @@ static unsigned long cache_alloc_handle(

p = kmem_cache_alloc(pool->handle_cachep,
gfp & ~(__GFP_HIGHMEM|__GFP_MOVABLE));
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
if (p) {
struct zsmalloc_handle *zh = p;

@@ -377,10 +380,10 @@ static unsigned long cache_alloc_handle(
return (unsigned long)p;
}

-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
static struct zsmalloc_handle *zs_get_pure_handle(unsigned long handle)
{
- return (void *)(handle &~((1 << OBJ_TAG_BITS) - 1));
+ return (void *)(handle & ~BIT(HANDLE_PIN_BIT));
}
#endif

@@ -402,7 +405,7 @@ static void cache_free_zspage(struct zs_

static void record_obj(unsigned long handle, unsigned long obj)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

WRITE_ONCE(zh->addr, obj);
@@ -937,7 +940,7 @@ static unsigned long location_to_obj(str

static unsigned long handle_to_obj(unsigned long handle)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

return zh->addr;
@@ -957,7 +960,7 @@ static unsigned long obj_to_head(struct

static inline int testpin_tag(unsigned long handle)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

return mutex_is_locked(&zh->lock);
@@ -968,7 +971,7 @@ static inline int testpin_tag(unsigned l

static inline int trypin_tag(unsigned long handle)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

return mutex_trylock(&zh->lock);
@@ -979,7 +982,7 @@ static inline int trypin_tag(unsigned lo

static void pin_tag(unsigned long handle)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

return mutex_lock(&zh->lock);
@@ -990,7 +993,7 @@ static void pin_tag(unsigned long handle

static void unpin_tag(unsigned long handle)
{
-#ifdef CONFIG_PREEMPT_RT_BASE
+#ifdef CONFIG_PREEMPT_RT_FULL
struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

return mutex_unlock(&zh->lock);
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