1 /* 2 * Compressed RAM block device 3 * 4 * Copyright (C) 2008, 2009, 2010 Nitin Gupta 5 * 2012, 2013 Minchan Kim 6 * 7 * This code is released using a dual license strategy: BSD/GPL 8 * You can choose the licence that better fits your requirements. 9 * 10 * Released under the terms of 3-clause BSD License 11 * Released under the terms of GNU General Public License Version 2.0 12 * 13 */ 14 15 #ifndef _ZRAM_DRV_H_ 16 #define _ZRAM_DRV_H_ 17 18 #include <linux/spinlock.h> 19 #include <linux/zsmalloc.h> 20 21 #include "zcomp.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 /*-- Configurable parameters */ 30 31 /* 32 * Pages that compress to size greater than this are stored 33 * uncompressed in memory. 34 */ 35 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; 36 37 /* 38 * NOTE: max_zpage_size must be less than or equal to: 39 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would 40 * always return failure. 41 */ 42 43 /*-- End of configurable params */ 44 45 #define SECTOR_SHIFT 9 46 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) 47 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) 48 #define ZRAM_LOGICAL_BLOCK_SHIFT 12 49 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT) 50 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \ 51 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT)) 52 53 54 /* 55 * The lower ZRAM_FLAG_SHIFT bits of table.value is for 56 * object size (excluding header), the higher bits is for 57 * zram_pageflags. 58 * 59 * zram is mainly used for memory efficiency so we want to keep memory 60 * footprint small so we can squeeze size and flags into a field. 61 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), 62 * the higher bits is for zram_pageflags. 63 */ 64 #define ZRAM_FLAG_SHIFT 24 65 66 /* Flags for zram pages (table[page_no].value) */ 67 enum zram_pageflags { 68 /* Page consists entirely of zeros */ 69 ZRAM_ZERO = ZRAM_FLAG_SHIFT, 70 ZRAM_ACCESS, /* page is now accessed */ 71 72 __NR_ZRAM_PAGEFLAGS, 73 }; 74 75 /*-- Data structures */ 76 77 /* Allocated for each disk page */ 78 struct zram_table_entry { 79 unsigned long handle; 80 unsigned long value; 81 }; 82 83 struct zram_stats { 84 atomic64_t compr_data_size; /* compressed size of pages stored */ 85 atomic64_t num_reads; /* failed + successful */ 86 atomic64_t num_writes; /* --do-- */ 87 atomic64_t failed_reads; /* can happen when memory is too low */ 88 atomic64_t failed_writes; /* can happen when memory is too low */ 89 atomic64_t invalid_io; /* non-page-aligned I/O requests */ 90 atomic64_t notify_free; /* no. of swap slot free notifications */ 91 atomic64_t zero_pages; /* no. of zero filled pages */ 92 atomic64_t pages_stored; /* no. of pages currently stored */ 93 atomic_long_t max_used_pages; /* no. of maximum pages stored */ 94 }; 95 96 struct zram_meta { 97 struct zram_table_entry *table; 98 struct zs_pool *mem_pool; 99 }; 100 101 struct zram { 102 struct zram_meta *meta; 103 struct zcomp *comp; 104 struct gendisk *disk; 105 /* Prevent concurrent execution of device init */ 106 struct rw_semaphore init_lock; 107 /* 108 * the number of pages zram can consume for storing compressed data 109 */ 110 unsigned long limit_pages; 111 int max_comp_streams; 112 113 struct zram_stats stats; 114 atomic_t refcount; /* refcount for zram_meta */ 115 /* wait all IO under all of cpu are done */ 116 wait_queue_head_t io_done; 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 char compressor[10]; 123 }; 124 #endif 125