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 /*-- Configurable parameters */ 24 25 /* 26 * Pages that compress to size greater than this are stored 27 * uncompressed in memory. 28 */ 29 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; 30 31 /* 32 * NOTE: max_zpage_size must be less than or equal to: 33 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would 34 * always return failure. 35 */ 36 37 /*-- End of configurable params */ 38 39 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) 40 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) 41 #define ZRAM_LOGICAL_BLOCK_SHIFT 12 42 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT) 43 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \ 44 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT)) 45 46 47 /* 48 * The lower ZRAM_FLAG_SHIFT bits of table.value is for 49 * object size (excluding header), the higher bits is for 50 * zram_pageflags. 51 * 52 * zram is mainly used for memory efficiency so we want to keep memory 53 * footprint small so we can squeeze size and flags into a field. 54 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), 55 * the higher bits is for zram_pageflags. 56 */ 57 #define ZRAM_FLAG_SHIFT 24 58 59 /* Flags for zram pages (table[page_no].value) */ 60 enum zram_pageflags { 61 /* Page consists entirely of zeros */ 62 ZRAM_ZERO = ZRAM_FLAG_SHIFT, 63 ZRAM_ACCESS, /* page is now accessed */ 64 65 __NR_ZRAM_PAGEFLAGS, 66 }; 67 68 /*-- Data structures */ 69 70 /* Allocated for each disk page */ 71 struct zram_table_entry { 72 unsigned long handle; 73 unsigned long value; 74 }; 75 76 struct zram_stats { 77 atomic64_t compr_data_size; /* compressed size of pages stored */ 78 atomic64_t num_reads; /* failed + successful */ 79 atomic64_t num_writes; /* --do-- */ 80 atomic64_t failed_reads; /* can happen when memory is too low */ 81 atomic64_t failed_writes; /* can happen when memory is too low */ 82 atomic64_t invalid_io; /* non-page-aligned I/O requests */ 83 atomic64_t notify_free; /* no. of swap slot free notifications */ 84 atomic64_t zero_pages; /* no. of zero filled pages */ 85 atomic64_t pages_stored; /* no. of pages currently stored */ 86 atomic_long_t max_used_pages; /* no. of maximum pages stored */ 87 }; 88 89 struct zram_meta { 90 struct zram_table_entry *table; 91 struct zs_pool *mem_pool; 92 }; 93 94 struct zram { 95 struct zram_meta *meta; 96 struct zcomp *comp; 97 struct gendisk *disk; 98 /* Prevent concurrent execution of device init */ 99 struct rw_semaphore init_lock; 100 /* 101 * the number of pages zram can consume for storing compressed data 102 */ 103 unsigned long limit_pages; 104 int max_comp_streams; 105 106 struct zram_stats stats; 107 atomic_t refcount; /* refcount for zram_meta */ 108 /* wait all IO under all of cpu are done */ 109 wait_queue_head_t io_done; 110 /* 111 * This is the limit on amount of *uncompressed* worth of data 112 * we can store in a disk. 113 */ 114 u64 disksize; /* bytes */ 115 char compressor[10]; 116 /* 117 * zram is claimed so open request will be failed 118 */ 119 bool claim; /* Protected by bdev->bd_mutex */ 120 }; 121 #endif 122