Re: [PATCH] mm/zsmalloc.c: Fix zsmalloc 32-bit PAE support

[kbuild test robot <lkp@intel.com>]

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Hi Rafael,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v4.20-rc6 next-20181212]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Rafael-David-Tinoco/mm-zsmalloc-c-Fix-zsmalloc-32-bit-PAE-support/20181211-020704
config: mips-allmodconfig (attached as .config)
compiler: mips-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        GCC_VERSION=7.2.0 make.cross ARCH=mips 

All error/warnings (new ones prefixed by >>):

>> mm/zsmalloc.c:116:5: error: #error "MAX_POSSIBLE_PHYSMEM_BITS is wrong for this arch";
       #error "MAX_POSSIBLE_PHYSMEM_BITS is wrong for this arch";
        ^~~~~
   In file included from include/linux/cache.h:5:0,
                    from arch/mips/include/asm/cpu-info.h:15,
                    from arch/mips/include/asm/cpu-features.h:13,
                    from arch/mips/include/asm/bitops.h:21,
                    from include/linux/bitops.h:19,
                    from include/linux/kernel.h:11,
                    from include/linux/list.h:9,
                    from include/linux/module.h:9,
                    from mm/zsmalloc.c:33:
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/uapi/linux/kernel.h:13:40: note: in definition of macro '__KERNEL_DIV_ROUND_UP'
    #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
>> mm/zsmalloc.c:151:59: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
    #define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
                                                              ^~~~~~~~~~~~~~~~~
>> mm/zsmalloc.c:256:32: note: in expansion of macro 'ZS_SIZE_CLASSES'
     struct size_class *size_class[ZS_SIZE_CLASSES];
                                   ^~~~~~~~~~~~~~~
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/uapi/linux/kernel.h:13:40: note: in definition of macro '__KERNEL_DIV_ROUND_UP'
    #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
>> mm/zsmalloc.c:151:59: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
    #define ZS_SIZE_CLASSES (DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
                                                              ^~~~~~~~~~~~~~~~~
>> mm/zsmalloc.c:256:32: note: in expansion of macro 'ZS_SIZE_CLASSES'
     struct size_class *size_class[ZS_SIZE_CLASSES];
                                   ^~~~~~~~~~~~~~~
>> mm/zsmalloc.c:256:21: error: variably modified 'size_class' at file scope
     struct size_class *size_class[ZS_SIZE_CLASSES];
                        ^~~~~~~~~~
   In file included from include/linux/kernel.h:10:0,
                    from include/linux/list.h:9,
                    from include/linux/module.h:9,
                    from mm/zsmalloc.c:33:
   mm/zsmalloc.c: In function 'get_size_class_index':
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/linux/compiler.h:76:40: note: in definition of macro 'likely'
    # define likely(x) __builtin_expect(!!(x), 1)
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
   mm/zsmalloc.c:543:20: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
     if (likely(size > ZS_MIN_ALLOC_SIZE))
                       ^~~~~~~~~~~~~~~~~
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/linux/compiler.h:76:40: note: in definition of macro 'likely'
    # define likely(x) __builtin_expect(!!(x), 1)
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
   mm/zsmalloc.c:543:20: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
     if (likely(size > ZS_MIN_ALLOC_SIZE))
                       ^~~~~~~~~~~~~~~~~
   In file included from include/linux/cache.h:5:0,
                    from arch/mips/include/asm/cpu-info.h:15,
                    from arch/mips/include/asm/cpu-features.h:13,
                    from arch/mips/include/asm/bitops.h:21,
                    from include/linux/bitops.h:19,
                    from include/linux/kernel.h:11,
                    from include/linux/list.h:9,
                    from include/linux/module.h:9,
                    from mm/zsmalloc.c:33:
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/uapi/linux/kernel.h:13:40: note: in definition of macro '__KERNEL_DIV_ROUND_UP'
    #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
   mm/zsmalloc.c:544:29: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
      idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
                                ^~~~~~~~~~~~~~~~~
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/uapi/linux/kernel.h:13:40: note: in definition of macro '__KERNEL_DIV_ROUND_UP'
    #define __KERNEL_DIV_ROUND_UP(n, d) (((n) + (d) - 1) / (d))
                                           ^
>> mm/zsmalloc.c:133:2: note: in expansion of macro 'MAX'
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
     ^~~
   mm/zsmalloc.c:544:29: note: in expansion of macro 'ZS_MIN_ALLOC_SIZE'
      idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
                                ^~~~~~~~~~~~~~~~~
   In file included from include/linux/list.h:9:0,
                    from include/linux/module.h:9,
                    from mm/zsmalloc.c:33:
>> mm/zsmalloc.c:133:49: warning: right shift count is negative [-Wshift-count-negative]
     MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
                                                    ^
   include/linux/kernel.h:861:27: note: in definition of macro '__cmp'
    #define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
                              ^
   include/linux/kernel.h:937:27: note: in expansion of macro '__careful_cmp'
    #define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <)
                              ^~~~~~~~~~~~~
>> mm/zsmalloc.c:547:9: note: in expansion of macro 'min_t'
     return min_t(int, ZS_SIZE_CLASSES - 1, idx);
            ^~~~~

vim +116 mm/zsmalloc.c

    32	
  > 33	#include <linux/module.h>
    34	#include <linux/kernel.h>
    35	#include <linux/sched.h>
    36	#include <linux/magic.h>
    37	#include <linux/bitops.h>
    38	#include <linux/errno.h>
    39	#include <linux/highmem.h>
    40	#include <linux/string.h>
    41	#include <linux/slab.h>
    42	#include <asm/tlbflush.h>
    43	#include <asm/pgtable.h>
    44	#include <linux/cpumask.h>
    45	#include <linux/cpu.h>
    46	#include <linux/vmalloc.h>
    47	#include <linux/preempt.h>
    48	#include <linux/spinlock.h>
    49	#include <linux/shrinker.h>
    50	#include <linux/types.h>
    51	#include <linux/debugfs.h>
    52	#include <linux/zsmalloc.h>
    53	#include <linux/zpool.h>
    54	#include <linux/mount.h>
    55	#include <linux/migrate.h>
    56	#include <linux/pagemap.h>
    57	#include <linux/fs.h>
    58	
    59	#define ZSPAGE_MAGIC	0x58
    60	
    61	/*
    62	 * This must be power of 2 and greater than of equal to sizeof(link_free).
    63	 * These two conditions ensure that any 'struct link_free' itself doesn't
    64	 * span more than 1 page which avoids complex case of mapping 2 pages simply
    65	 * to restore link_free pointer values.
    66	 */
    67	#define ZS_ALIGN		8
    68	
    69	/*
    70	 * A single 'zspage' is composed of up to 2^N discontiguous 0-order (single)
    71	 * pages. ZS_MAX_ZSPAGE_ORDER defines upper limit on N.
    72	 */
    73	#define ZS_MAX_ZSPAGE_ORDER 2
    74	#define ZS_MAX_PAGES_PER_ZSPAGE (_AC(1, UL) << ZS_MAX_ZSPAGE_ORDER)
    75	
    76	#define ZS_HANDLE_SIZE (sizeof(unsigned long))
    77	
    78	/*
    79	 * Object location (<PFN>, <obj_idx>) is encoded as
    80	 * as single (unsigned long) handle value.
    81	 *
    82	 * Note that object index <obj_idx> starts from 0.
    83	 */
    84	
    85	/*
    86	 * Memory for allocating for handle keeps object position by
    87	 * encoding <page, obj_idx> and the encoded value has a room
    88	 * in least bit(ie, look at obj_to_location).
    89	 * We use the bit to synchronize between object access by
    90	 * user and migration.
    91	 */
    92	#define HANDLE_PIN_BIT	0
    93	
    94	/*
    95	 * Head in allocated object should have OBJ_ALLOCATED_TAG
    96	 * to identify the object was allocated or not.
    97	 * It's okay to add the status bit in the least bit because
    98	 * header keeps handle which is 4byte-aligned address so we
    99	 * have room for two bit at least.
   100	 */
   101	#define OBJ_ALLOCATED_TAG 1
   102	#define OBJ_TAG_BITS 1
   103	
   104	/*
   105	 * MAX_POSSIBLE_PHYSMEM_BITS should be defined by all archs using zsmalloc:
   106	 * Trying to guess it from MAX_PHYSMEM_BITS, or considering it BITS_PER_LONG,
   107	 * proved to be wrong by not considering PAE capabilities, or using SPARSEMEM
   108	 * only headers, leading to bad object encoding due to object index overflow.
   109	 */
   110	#ifndef MAX_POSSIBLE_PHYSMEM_BITS
   111	 #define MAX_POSSIBLE_PHYSMEM_BITS BITS_PER_LONG
   112	 #error "MAX_POSSIBLE_PHYSMEM_BITS HAS to be defined by arch using zsmalloc";
   113	#else
   114	 #ifndef CONFIG_64BIT
   115	  #if (MAX_POSSIBLE_PHYSMEM_BITS >= (BITS_PER_LONG + PAGE_SHIFT - OBJ_TAG_BITS))
 > 116	   #error "MAX_POSSIBLE_PHYSMEM_BITS is wrong for this arch";
   117	  #endif
   118	 #endif
   119	#endif
   120	
   121	#define _PFN_BITS (MAX_POSSIBLE_PHYSMEM_BITS - PAGE_SHIFT)
   122	#define OBJ_INDEX_BITS	(BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
 > 123	#define OBJ_INDEX_MASK	((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
   124	
   125	#define FULLNESS_BITS	2
   126	#define CLASS_BITS	8
   127	#define ISOLATED_BITS	3
   128	#define MAGIC_VAL_BITS	8
   129	
   130	#define MAX(a, b) ((a) >= (b) ? (a) : (b))
   131	/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
   132	#define ZS_MIN_ALLOC_SIZE \
 > 133		MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
   134	/* each chunk includes extra space to keep handle */
   135	#define ZS_MAX_ALLOC_SIZE	PAGE_SIZE
   136	
   137	/*
   138	 * On systems with 4K page size, this gives 255 size classes! There is a
   139	 * trader-off here:
   140	 *  - Large number of size classes is potentially wasteful as free page are
   141	 *    spread across these classes
   142	 *  - Small number of size classes causes large internal fragmentation
   143	 *  - Probably its better to use specific size classes (empirically
   144	 *    determined). NOTE: all those class sizes must be set as multiple of
   145	 *    ZS_ALIGN to make sure link_free itself never has to span 2 pages.
   146	 *
   147	 *  ZS_MIN_ALLOC_SIZE and ZS_SIZE_CLASS_DELTA must be multiple of ZS_ALIGN
   148	 *  (reason above)
   149	 */
   150	#define ZS_SIZE_CLASS_DELTA	(PAGE_SIZE >> CLASS_BITS)
 > 151	#define ZS_SIZE_CLASSES	(DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
   152					      ZS_SIZE_CLASS_DELTA) + 1)
   153	
   154	enum fullness_group {
   155		ZS_EMPTY,
   156		ZS_ALMOST_EMPTY,
   157		ZS_ALMOST_FULL,
   158		ZS_FULL,
   159		NR_ZS_FULLNESS,
   160	};
   161	
   162	enum zs_stat_type {
   163		CLASS_EMPTY,
   164		CLASS_ALMOST_EMPTY,
   165		CLASS_ALMOST_FULL,
   166		CLASS_FULL,
   167		OBJ_ALLOCATED,
   168		OBJ_USED,
   169		NR_ZS_STAT_TYPE,
   170	};
   171	
   172	struct zs_size_stat {
   173		unsigned long objs[NR_ZS_STAT_TYPE];
   174	};
   175	
   176	#ifdef CONFIG_ZSMALLOC_STAT
   177	static struct dentry *zs_stat_root;
   178	#endif
   179	
   180	#ifdef CONFIG_COMPACTION
   181	static struct vfsmount *zsmalloc_mnt;
   182	#endif
   183	
   184	/*
   185	 * We assign a page to ZS_ALMOST_EMPTY fullness group when:
   186	 *	n <= N / f, where
   187	 * n = number of allocated objects
   188	 * N = total number of objects zspage can store
   189	 * f = fullness_threshold_frac
   190	 *
   191	 * Similarly, we assign zspage to:
   192	 *	ZS_ALMOST_FULL	when n > N / f
   193	 *	ZS_EMPTY	when n == 0
   194	 *	ZS_FULL		when n == N
   195	 *
   196	 * (see: fix_fullness_group())
   197	 */
   198	static const int fullness_threshold_frac = 4;
   199	static size_t huge_class_size;
   200	
   201	struct size_class {
   202		spinlock_t lock;
   203		struct list_head fullness_list[NR_ZS_FULLNESS];
   204		/*
   205		 * Size of objects stored in this class. Must be multiple
   206		 * of ZS_ALIGN.
   207		 */
   208		int size;
   209		int objs_per_zspage;
   210		/* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
   211		int pages_per_zspage;
   212	
   213		unsigned int index;
   214		struct zs_size_stat stats;
   215	};
   216	
   217	/* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
   218	static void SetPageHugeObject(struct page *page)
   219	{
   220		SetPageOwnerPriv1(page);
   221	}
   222	
   223	static void ClearPageHugeObject(struct page *page)
   224	{
   225		ClearPageOwnerPriv1(page);
   226	}
   227	
   228	static int PageHugeObject(struct page *page)
   229	{
   230		return PageOwnerPriv1(page);
   231	}
   232	
   233	/*
   234	 * Placed within free objects to form a singly linked list.
   235	 * For every zspage, zspage->freeobj gives head of this list.
   236	 *
   237	 * This must be power of 2 and less than or equal to ZS_ALIGN
   238	 */
   239	struct link_free {
   240		union {
   241			/*
   242			 * Free object index;
   243			 * It's valid for non-allocated object
   244			 */
   245			unsigned long next;
   246			/*
   247			 * Handle of allocated object.
   248			 */
   249			unsigned long handle;
   250		};
   251	};
   252	
   253	struct zs_pool {
   254		const char *name;
   255	
 > 256		struct size_class *size_class[ZS_SIZE_CLASSES];
   257		struct kmem_cache *handle_cachep;
   258		struct kmem_cache *zspage_cachep;
   259	
   260		atomic_long_t pages_allocated;
   261	
   262		struct zs_pool_stats stats;
   263	
   264		/* Compact classes */
   265		struct shrinker shrinker;
   266	

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