1 /* 2 * Compressed RAM block device 3 * 4 * Copyright (C) 2008, 2009, 2010 Nitin Gupta 5 * 6 * This code is released using a dual license strategy: BSD/GPL 7 * You can choose the licence that better fits your requirements. 8 * 9 * Released under the terms of 3-clause BSD License 10 * Released under the terms of GNU General Public License Version 2.0 11 * 12 * Project home: http://compcache.googlecode.com 13 */ 14 15 #ifndef _ZRAM_DRV_H_ 16 #define _ZRAM_DRV_H_ 17 18 #include <linux/spinlock.h> 19 #include <linux/mutex.h> 20 21 #include "../zsmalloc/zsmalloc.h" 22 23 /* 24 * Some arbitrary value. This is just to catch 25 * invalid value for num_devices module parameter. 26 */ 27 static const unsigned max_num_devices = 32; 28 29 /* 30 * Stored at beginning of each compressed object. 31 * 32 * It stores back-reference to table entry which points to this 33 * object. This is required to support memory defragmentation. 34 */ 35 struct zobj_header { 36 #if 0 37 u32 table_idx; 38 #endif 39 }; 40 41 /*-- Configurable parameters */ 42 43 /* Default zram disk size: 25% of total RAM */ 44 static const unsigned default_disksize_perc_ram = 25; 45 46 /* 47 * Pages that compress to size greater than this are stored 48 * uncompressed in memory. 49 */ 50 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; 51 52 /* 53 * NOTE: max_zpage_size must be less than or equal to: 54 * ZS_MAX_ALLOC_SIZE - sizeof(struct zobj_header) 55 * otherwise, xv_malloc() would always return failure. 56 */ 57 58 /*-- End of configurable params */ 59 60 #define SECTOR_SHIFT 9 61 #define SECTOR_SIZE (1 << SECTOR_SHIFT) 62 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) 63 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) 64 #define ZRAM_LOGICAL_BLOCK_SHIFT 12 65 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT) 66 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \ 67 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT)) 68 69 /* Flags for zram pages (table[page_no].flags) */ 70 enum zram_pageflags { 71 /* Page is stored uncompressed */ 72 ZRAM_UNCOMPRESSED, 73 74 /* Page consists entirely of zeros */ 75 ZRAM_ZERO, 76 77 __NR_ZRAM_PAGEFLAGS, 78 }; 79 80 /*-- Data structures */ 81 82 /* Allocated for each disk page */ 83 struct table { 84 void *handle; 85 u16 size; /* object size (excluding header) */ 86 u8 count; /* object ref count (not yet used) */ 87 u8 flags; 88 } __attribute__((aligned(4))); 89 90 struct zram_stats { 91 u64 compr_size; /* compressed size of pages stored */ 92 u64 num_reads; /* failed + successful */ 93 u64 num_writes; /* --do-- */ 94 u64 failed_reads; /* should NEVER! happen */ 95 u64 failed_writes; /* can happen when memory is too low */ 96 u64 invalid_io; /* non-page-aligned I/O requests */ 97 u64 notify_free; /* no. of swap slot free notifications */ 98 u32 pages_zero; /* no. of zero filled pages */ 99 u32 pages_stored; /* no. of pages currently stored */ 100 u32 good_compress; /* % of pages with compression ratio<=50% */ 101 u32 pages_expand; /* % of incompressible pages */ 102 }; 103 104 struct zram { 105 struct zs_pool *mem_pool; 106 void *compress_workmem; 107 void *compress_buffer; 108 struct table *table; 109 spinlock_t stat64_lock; /* protect 64-bit stats */ 110 struct rw_semaphore lock; /* protect compression buffers and table 111 * against concurrent read and writes */ 112 struct request_queue *queue; 113 struct gendisk *disk; 114 int init_done; 115 /* Prevent concurrent execution of device init, reset and R/W request */ 116 struct rw_semaphore init_lock; 117 /* 118 * This is the limit on amount of *uncompressed* worth of data 119 * we can store in a disk. 120 */ 121 u64 disksize; /* bytes */ 122 123 struct zram_stats stats; 124 }; 125 126 extern struct zram *zram_devices; 127 unsigned int zram_get_num_devices(void); 128 #ifdef CONFIG_SYSFS 129 extern struct attribute_group zram_disk_attr_group; 130 #endif 131 132 extern int zram_init_device(struct zram *zram); 133 extern void __zram_reset_device(struct zram *zram); 134 135 #endif 136