/*
 * Compressed RAM block device
 *
 * Copyright (C) 2008, 2009, 2010  Nitin Gupta
 *               2012, 2013 Minchan Kim
 *
 * This code is released using a dual license strategy: BSD/GPL
 * You can choose the licence that better fits your requirements.
 *
 * Released under the terms of 3-clause BSD License
 * Released under the terms of GNU General Public License Version 2.0
 *
 */

#ifndef _ZRAM_DRV_H_
#define _ZRAM_DRV_H_

#include <linux/rwsem.h>
#include <linux/zsmalloc.h>

#include "zcomp.h"

#define SECTORS_PER_PAGE_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)
#define SECTORS_PER_PAGE        (1 << SECTORS_PER_PAGE_SHIFT)
#define ZRAM_LOGICAL_BLOCK_SHIFT 12
#define ZRAM_LOGICAL_BLOCK_SIZE (1 << ZRAM_LOGICAL_BLOCK_SHIFT)
#define ZRAM_SECTOR_PER_LOGICAL_BLOCK   \
        (1 << (ZRAM_LOGICAL_BLOCK_SHIFT - SECTOR_SHIFT))

/*
 * ZRAM is mainly used for memory efficiency so we want to keep memory
 * footprint small and thus squeeze size and zram pageflags into a flags
 * member. The lower ZRAM_FLAG_SHIFT bits is for object size (excluding
 * header), which cannot be larger than PAGE_SIZE (requiring PAGE_SHIFT
 * bits), the higher bits are for zram_pageflags.
 *
 * We use BUILD_BUG_ON() to make sure that zram pageflags don't overflow.
 */
#define ZRAM_FLAG_SHIFT (PAGE_SHIFT + 1)

/* Only 2 bits are allowed for comp priority index */
#define ZRAM_COMP_PRIORITY_MASK 0x3

/* Flags for zram pages (table[page_no].flags) */
enum zram_pageflags {
        ZRAM_SAME = ZRAM_FLAG_SHIFT,    /* Page consists the same element */
        ZRAM_ENTRY_LOCK, /* entry access lock bit */
        ZRAM_WB,        /* page is stored on backing_device */
        ZRAM_PP_SLOT,   /* Selected for post-processing */
        ZRAM_HUGE,      /* Incompressible page */
        ZRAM_IDLE,      /* not accessed page since last idle marking */
        ZRAM_INCOMPRESSIBLE, /* none of the algorithms could compress it */

        ZRAM_COMP_PRIORITY_BIT1, /* First bit of comp priority index */
        ZRAM_COMP_PRIORITY_BIT2, /* Second bit of comp priority index */

        __NR_ZRAM_PAGEFLAGS,
};

/*
 * Allocated for each disk page.  We use bit-lock (ZRAM_ENTRY_LOCK bit
 * of flags) to save memory.  There can be plenty of entries and standard
 * locking primitives (e.g. mutex) will significantly increase sizeof()
 * of each entry and hence of the meta table.
 */
struct zram_table_entry {
        unsigned long handle;
        union {
                unsigned long __lock;
                struct attr {
                        u32 flags;
#ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
                        u32 ac_time;
#endif
                } attr;
        };
        struct lockdep_map dep_map;
};

struct zram_stats {
        atomic64_t compr_data_size;     /* compressed size of pages stored */
        atomic64_t failed_reads;        /* can happen when memory is too low */
        atomic64_t failed_writes;       /* can happen when memory is too low */
        atomic64_t notify_free; /* no. of swap slot free notifications */
        atomic64_t same_pages;          /* no. of same element filled pages */
        atomic64_t huge_pages;          /* no. of huge pages */
        atomic64_t huge_pages_since;    /* no. of huge pages since zram set up */
        atomic64_t pages_stored;        /* no. of pages currently stored */
        atomic_long_t max_used_pages;   /* no. of maximum pages stored */
        atomic64_t miss_free;           /* no. of missed free */
#ifdef  CONFIG_ZRAM_WRITEBACK
        atomic64_t bd_count;            /* no. of pages in backing device */
        atomic64_t bd_reads;            /* no. of reads from backing device */
        atomic64_t bd_writes;           /* no. of writes from backing device */
#endif
};

#ifdef CONFIG_ZRAM_MULTI_COMP
#define ZRAM_PRIMARY_COMP       0U
#define ZRAM_SECONDARY_COMP     1U
#define ZRAM_MAX_COMPS  4U
#else
#define ZRAM_PRIMARY_COMP       0U
#define ZRAM_SECONDARY_COMP     0U
#define ZRAM_MAX_COMPS  1U
#endif

struct zram {
        struct zram_table_entry *table;
        struct zs_pool *mem_pool;
        struct zcomp *comps[ZRAM_MAX_COMPS];
        struct zcomp_params params[ZRAM_MAX_COMPS];
        struct gendisk *disk;
        /* Locks the device either in exclusive or in shared mode */
        struct rw_semaphore dev_lock;
        /*
         * the number of pages zram can consume for storing compressed data
         */
        unsigned long limit_pages;

        struct zram_stats stats;
        /*
         * This is the limit on amount of *uncompressed* worth of data
         * we can store in a disk.
         */
        u64 disksize;   /* bytes */
        const char *comp_algs[ZRAM_MAX_COMPS];
        s8 num_active_comps;
        /*
         * zram is claimed so open request will be failed
         */
        bool claim; /* Protected by disk->open_mutex */
#ifdef CONFIG_ZRAM_WRITEBACK
        struct file *backing_dev;
        bool wb_limit_enable;
        bool compressed_wb;
        u32 wb_batch_size;
        u64 bd_wb_limit;
        struct block_device *bdev;
        unsigned long *bitmap;
        unsigned long nr_pages;
#endif
#ifdef CONFIG_ZRAM_MEMORY_TRACKING
        struct dentry *debugfs_dir;
#endif
};
#endif