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/mutex.h> 20 #include <linux/zsmalloc.h> 21 22 /* 23 * Some arbitrary value. This is just to catch 24 * invalid value for num_devices module parameter. 25 */ 26 static const unsigned max_num_devices = 32; 27 28 /*-- Configurable parameters */ 29 30 /* 31 * Pages that compress to size greater than this are stored 32 * uncompressed in memory. 33 */ 34 static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; 35 36 /* 37 * NOTE: max_zpage_size must be less than or equal to: 38 * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would 39 * always return failure. 40 */ 41 42 /*-- End of configurable params */ 43 44 #define SECTOR_SHIFT 9 45 #define SECTOR_SIZE (1 << SECTOR_SHIFT) 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 /* Flags for zram pages (table[page_no].flags) */ 54 enum zram_pageflags { 55 /* Page consists entirely of zeros */ 56 ZRAM_ZERO, 57 58 __NR_ZRAM_PAGEFLAGS, 59 }; 60 61 /*-- Data structures */ 62 63 /* Allocated for each disk page */ 64 struct table { 65 unsigned long handle; 66 u16 size; /* object size (excluding header) */ 67 u8 count; /* object ref count (not yet used) */ 68 u8 flags; 69 } __aligned(4); 70 71 struct zram_stats { 72 atomic64_t compr_size; /* compressed size of pages stored */ 73 atomic64_t num_reads; /* failed + successful */ 74 atomic64_t num_writes; /* --do-- */ 75 atomic64_t failed_reads; /* should NEVER! happen */ 76 atomic64_t failed_writes; /* can happen when memory is too low */ 77 atomic64_t invalid_io; /* non-page-aligned I/O requests */ 78 atomic64_t notify_free; /* no. of swap slot free notifications */ 79 atomic_t pages_zero; /* no. of zero filled pages */ 80 atomic_t pages_stored; /* no. of pages currently stored */ 81 atomic_t good_compress; /* % of pages with compression ratio<=50% */ 82 atomic_t bad_compress; /* % of pages with compression ratio>=75% */ 83 }; 84 85 struct zram_meta { 86 rwlock_t tb_lock; /* protect table */ 87 void *compress_workmem; 88 void *compress_buffer; 89 struct table *table; 90 struct zs_pool *mem_pool; 91 struct mutex buffer_lock; /* protect compress buffers */ 92 }; 93 94 struct zram { 95 struct zram_meta *meta; 96 struct request_queue *queue; 97 struct gendisk *disk; 98 int init_done; 99 /* Prevent concurrent execution of device init, reset and R/W request */ 100 struct rw_semaphore init_lock; 101 /* 102 * This is the limit on amount of *uncompressed* worth of data 103 * we can store in a disk. 104 */ 105 u64 disksize; /* bytes */ 106 107 struct zram_stats stats; 108 }; 109 #endif 110