136 lines
3.5 KiB
C
136 lines
3.5 KiB
C
/*
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* Compressed RAM block device
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*
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* Copyright (C) 2008, 2009, 2010 Nitin Gupta
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*
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* This code is released using a dual license strategy: BSD/GPL
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* You can choose the licence that better fits your requirements.
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*
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* Released under the terms of 3-clause BSD License
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* Released under the terms of GNU General Public License Version 2.0
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*
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* Project home: http://compcache.googlecode.com
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*/
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#ifndef _ZRAM_DRV_H_
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#define _ZRAM_DRV_H_
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#include <linux/spinlock.h>
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#include <linux/mutex.h>
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#include "xvmalloc.h"
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/*
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* Some arbitrary value. This is just to catch
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* invalid value for num_devices module parameter.
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*/
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static const unsigned max_num_devices = 32;
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/*
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* Stored at beginning of each compressed object.
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*
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* It stores back-reference to table entry which points to this
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* object. This is required to support memory defragmentation.
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*/
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struct zobj_header {
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#if 0
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u32 table_idx;
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#endif
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};
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/*-- Configurable parameters */
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/* Default zram disk size: 25% of total RAM */
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static const unsigned default_disksize_perc_ram = 25;
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/*
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* Pages that compress to size greater than this are stored
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* uncompressed in memory.
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*/
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static const unsigned max_zpage_size = PAGE_SIZE / 4 * 3;
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/*
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* NOTE: max_zpage_size must be less than or equal to:
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* XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
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* otherwise, xv_malloc() would always return failure.
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*/
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/*-- End of configurable params */
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#define SECTOR_SHIFT 9
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#define SECTOR_SIZE (1 << SECTOR_SHIFT)
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#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
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#define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
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#define ZRAM_LOGICAL_BLOCK_SHIFT 12
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#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
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#define ZRAM_SECTOR_PER_LOGICAL_BLOCK \
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(1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))
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/* Flags for zram pages (table[page_no].flags) */
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enum zram_pageflags {
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/* Page is stored uncompressed */
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ZRAM_UNCOMPRESSED,
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/* Page consists entirely of zeros */
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ZRAM_ZERO,
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__NR_ZRAM_PAGEFLAGS,
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};
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/*-- Data structures */
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/* Allocated for each disk page */
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struct table {
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struct page *page;
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u16 offset;
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u8 count; /* object ref count (not yet used) */
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u8 flags;
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} __attribute__((aligned(4)));
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struct zram_stats {
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u64 compr_size; /* compressed size of pages stored */
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u64 num_reads; /* failed + successful */
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u64 num_writes; /* --do-- */
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u64 failed_reads; /* should NEVER! happen */
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u64 failed_writes; /* can happen when memory is too low */
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u64 invalid_io; /* non-page-aligned I/O requests */
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u64 notify_free; /* no. of swap slot free notifications */
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u32 pages_zero; /* no. of zero filled pages */
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u32 pages_stored; /* no. of pages currently stored */
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u32 good_compress; /* % of pages with compression ratio<=50% */
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u32 pages_expand; /* % of incompressible pages */
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};
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struct zram {
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struct xv_pool *mem_pool;
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void *compress_workmem;
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void *compress_buffer;
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struct table *table;
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spinlock_t stat64_lock; /* protect 64-bit stats */
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struct mutex lock; /* protect compression buffers against
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* concurrent writes */
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struct request_queue *queue;
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struct gendisk *disk;
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int init_done;
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/* Prevent concurrent execution of device init and reset */
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struct mutex init_lock;
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/*
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* This is the limit on amount of *uncompressed* worth of data
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* we can store in a disk.
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*/
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u64 disksize; /* bytes */
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struct zram_stats stats;
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};
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extern struct zram *devices;
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extern unsigned int num_devices;
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#ifdef CONFIG_SYSFS
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extern struct attribute_group zram_disk_attr_group;
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#endif
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extern int zram_init_device(struct zram *zram);
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extern void zram_reset_device(struct zram *zram);
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#endif
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