[patch v2 ] mm/zs_malloc: Fix bit spinlock replacement

[Mike Galbraith]

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 <umgwanakikb...@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);