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 SECTOR_SHIFT 9 40 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) 41 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) 42 #define ZRAM_LOGICAL_BLOCK_SHIFT 12 43 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT) 44 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \ 45 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT)) 46 47 48 /* 49 * The lower ZRAM_FLAG_SHIFT bits of table.value is for 50 * object size (excluding header), the higher bits is for 51 * zram_pageflags. 52 * 53 * zram is mainly used for memory efficiency so we want to keep memory 54 * footprint small so we can squeeze size and flags into a field. 55 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), 56 * the higher bits is for zram_pageflags. 57 */ 58 #define ZRAM_FLAG_SHIFT 24 59 60 /* Flags for zram pages (table[page_no].value) */ 61 enum zram_pageflags { 62 /* Page consists entirely of zeros */ 63 ZRAM_ZERO = ZRAM_FLAG_SHIFT, 64 ZRAM_ACCESS, /* page is now accessed */ 65 66 __NR_ZRAM_PAGEFLAGS, 67 }; 68 69 /*-- Data structures */ 70 71 /* Allocated for each disk page */ 72 struct zram_table_entry { 73 unsigned long handle; 74 unsigned long value; 75 }; 76 77 struct zram_stats { 78 atomic64_t compr_data_size; /* compressed size of pages stored */ 79 atomic64_t num_reads; /* failed + successful */ 80 atomic64_t num_writes; /* --do-- */ 81 atomic64_t failed_reads; /* can happen when memory is too low */ 82 atomic64_t failed_writes; /* can happen when memory is too low */ 83 atomic64_t invalid_io; /* non-page-aligned I/O requests */ 84 atomic64_t notify_free; /* no. of swap slot free notifications */ 85 atomic64_t zero_pages; /* no. of zero filled pages */ 86 atomic64_t pages_stored; /* no. of pages currently stored */ 87 atomic_long_t max_used_pages; /* no. of maximum pages stored */ 88 atomic64_t writestall; /* no. of write slow paths */ 89 }; 90 91 struct zram_meta { 92 struct zram_table_entry *table; 93 struct zs_pool *mem_pool; 94 }; 95 96 struct zram { 97 struct zram_meta *meta; 98 struct zcomp *comp; 99 struct gendisk *disk; 100 /* Prevent concurrent execution of device init */ 101 struct rw_semaphore init_lock; 102 /* 103 * the number of pages zram can consume for storing compressed data 104 */ 105 unsigned long limit_pages; 106 107 struct zram_stats stats; 108 atomic_t refcount; /* refcount for zram_meta */ 109 /* wait all IO under all of cpu are done */ 110 wait_queue_head_t io_done; 111 /* 112 * This is the limit on amount of *uncompressed* worth of data 113 * we can store in a disk. 114 */ 115 u64 disksize; /* bytes */ 116 char compressor[10]; 117 /* 118 * zram is claimed so open request will be failed 119 */ 120 bool claim; /* Protected by bdev->bd_mutex */ 121 }; 122 #endif 123