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/rwsem.h> 19 #include <linux/zsmalloc.h> 20 #include <linux/crypto.h> 21 22 #include "zcomp.h" 23 24 /*-- Configurable parameters */ 25 26 /* 27 * Pages that compress to size greater than this are stored 28 * uncompressed in memory. 29 */ 30 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; 31 32 /* 33 * NOTE: max_zpage_size must be less than or equal to: 34 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would 35 * always return failure. 36 */ 37 38 /*-- End of configurable params */ 39 40 #define SECTOR_SHIFT 9 41 #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) 42 #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) 43 #define ZRAM_LOGICAL_BLOCK_SHIFT 12 44 #define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT) 45 #define ZRAM_SECTOR_PER_LOGICAL_BLOCK \ 46 (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT)) 47 48 49 /* 50 * The lower ZRAM_FLAG_SHIFT bits of table.value is for 51 * object size (excluding header), the higher bits is for 52 * zram_pageflags. 53 * 54 * zram is mainly used for memory efficiency so we want to keep memory 55 * footprint small so we can squeeze size and flags into a field. 56 * The lower ZRAM_FLAG_SHIFT bits is for object size (excluding header), 57 * the higher bits is for zram_pageflags. 58 */ 59 #define ZRAM_FLAG_SHIFT 24 60 61 /* Flags for zram pages (table[page_no].value) */ 62 enum zram_pageflags { 63 /* Page consists the same element */ 64 ZRAM_SAME = ZRAM_FLAG_SHIFT, 65 ZRAM_ACCESS, /* page is now accessed */ 66 ZRAM_WB, /* page is stored on backing_device */ 67 68 __NR_ZRAM_PAGEFLAGS, 69 }; 70 71 /*-- Data structures */ 72 73 /* Allocated for each disk page */ 74 struct zram_table_entry { 75 union { 76 unsigned long handle; 77 unsigned long element; 78 }; 79 unsigned long value; 80 }; 81 82 struct zram_stats { 83 atomic64_t compr_data_size; /* compressed size of pages stored */ 84 atomic64_t num_reads; /* failed + successful */ 85 atomic64_t num_writes; /* --do-- */ 86 atomic64_t failed_reads; /* can happen when memory is too low */ 87 atomic64_t failed_writes; /* can happen when memory is too low */ 88 atomic64_t invalid_io; /* non-page-aligned I/O requests */ 89 atomic64_t notify_free; /* no. of swap slot free notifications */ 90 atomic64_t same_pages; /* no. of same element filled pages */ 91 atomic64_t pages_stored; /* no. of pages currently stored */ 92 atomic_long_t max_used_pages; /* no. of maximum pages stored */ 93 atomic64_t writestall; /* no. of write slow paths */ 94 }; 95 96 struct zram { 97 struct zram_table_entry *table; 98 struct zs_pool *mem_pool; 99 struct zcomp *comp; 100 struct gendisk *disk; 101 /* Prevent concurrent execution of device init */ 102 struct rw_semaphore init_lock; 103 /* 104 * the number of pages zram can consume for storing compressed data 105 */ 106 unsigned long limit_pages; 107 108 struct zram_stats stats; 109 /* 110 * This is the limit on amount of *uncompressed* worth of data 111 * we can store in a disk. 112 */ 113 u64 disksize; /* bytes */ 114 char compressor[CRYPTO_MAX_ALG_NAME]; 115 /* 116 * zram is claimed so open request will be failed 117 */ 118 bool claim; /* Protected by bdev->bd_mutex */ 119 #ifdef CONFIG_ZRAM_WRITEBACK 120 struct file *backing_dev; 121 struct block_device *bdev; 122 unsigned int old_block_size; 123 unsigned long *bitmap; 124 unsigned long nr_pages; 125 spinlock_t bitmap_lock; 126 #endif 127 }; 128 #endif 129