/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (C) 2018 HUAWEI, Inc.
 *             https://www.huawei.com/
 */
#ifndef __EROFS_FS_ZDATA_H
#define __EROFS_FS_ZDATA_H

#include "internal.h"
#include "zpvec.h"

#define Z_EROFS_PCLUSTER_MAX_PAGES      (Z_EROFS_PCLUSTER_MAX_SIZE / PAGE_SIZE)
#define Z_EROFS_NR_INLINE_PAGEVECS      3

#define Z_EROFS_PCLUSTER_FULL_LENGTH    0x00000001
#define Z_EROFS_PCLUSTER_LENGTH_BIT     1

/*
 * let's leave a type here in case of introducing
 * another tagged pointer later.
 */
typedef void *z_erofs_next_pcluster_t;

/*
 * Structure fields follow one of the following exclusion rules.
 *
 * I: Modifiable by initialization/destruction paths and read-only
 *    for everyone else;
 *
 * L: Field should be protected by the pcluster lock;
 *
 * A: Field should be accessed / updated in atomic for parallelized code.
 */
struct z_erofs_pcluster {
        struct erofs_workgroup obj;
        struct mutex lock;

        /* A: point to next chained pcluster or TAILs */
        z_erofs_next_pcluster_t next;

        /* A: lower limit of decompressed length and if full length or not */
        unsigned int length;

        /* I: page offset of start position of decompression */
        unsigned short pageofs_out;

        /* I: page offset of inline compressed data */
        unsigned short pageofs_in;

        /* L: maximum relative page index in pagevec[] */
        unsigned short nr_pages;

        /* L: total number of pages in pagevec[] */
        unsigned int vcnt;

        union {
                /* L: inline a certain number of pagevecs for bootstrap */
                erofs_vtptr_t pagevec[Z_EROFS_NR_INLINE_PAGEVECS];

                /* I: can be used to free the pcluster by RCU. */
                struct rcu_head rcu;
        };

        union {
                /* I: physical cluster size in pages */
                unsigned short pclusterpages;

                /* I: tailpacking inline compressed size */
                unsigned short tailpacking_size;
        };

        /* I: compression algorithm format */
        unsigned char algorithmformat;

        /* A: compressed pages (can be cached or inplaced pages) */
        struct page *compressed_pages[];
};

/* let's avoid the valid 32-bit kernel addresses */

/* the chained workgroup has't submitted io (still open) */
#define Z_EROFS_PCLUSTER_TAIL           ((void *)0x5F0ECAFE)
/* the chained workgroup has already submitted io */
#define Z_EROFS_PCLUSTER_TAIL_CLOSED    ((void *)0x5F0EDEAD)

#define Z_EROFS_PCLUSTER_NIL            (NULL)

struct z_erofs_decompressqueue {
        struct super_block *sb;
        atomic_t pending_bios;
        z_erofs_next_pcluster_t head;

        union {
                struct completion done;
                struct work_struct work;
        } u;
};

static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
{
        return !pcl->obj.index;
}

static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
{
        if (z_erofs_is_inline_pcluster(pcl))
                return 1;
        return pcl->pclusterpages;
}

#define Z_EROFS_ONLINEPAGE_COUNT_BITS   2
#define Z_EROFS_ONLINEPAGE_COUNT_MASK   ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) - 1)
#define Z_EROFS_ONLINEPAGE_INDEX_SHIFT  (Z_EROFS_ONLINEPAGE_COUNT_BITS)

/*
 * waiters (aka. ongoing_packs): # to unlock the page
 * sub-index: 0 - for partial page, >= 1 full page sub-index
 */
typedef atomic_t z_erofs_onlinepage_t;

/* type punning */
union z_erofs_onlinepage_converter {
        z_erofs_onlinepage_t *o;
        unsigned long *v;
};

static inline unsigned int z_erofs_onlinepage_index(struct page *page)
{
        union z_erofs_onlinepage_converter u;

        DBG_BUGON(!PagePrivate(page));
        u.v = &page_private(page);

        return atomic_read(u.o) >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
}

static inline void z_erofs_onlinepage_init(struct page *page)
{
        union {
                z_erofs_onlinepage_t o;
                unsigned long v;
        /* keep from being unlocked in advance */
        } u = { .o = ATOMIC_INIT(1) };

        set_page_private(page, u.v);
        smp_wmb();
        SetPagePrivate(page);
}

static inline void z_erofs_onlinepage_fixup(struct page *page,
        uintptr_t index, bool down)
{
        union z_erofs_onlinepage_converter u = { .v = &page_private(page) };
        int orig, orig_index, val;

repeat:
        orig = atomic_read(u.o);
        orig_index = orig >> Z_EROFS_ONLINEPAGE_INDEX_SHIFT;
        if (orig_index) {
                if (!index)
                        return;

                DBG_BUGON(orig_index != index);
        }

        val = (index << Z_EROFS_ONLINEPAGE_INDEX_SHIFT) |
                ((orig & Z_EROFS_ONLINEPAGE_COUNT_MASK) + (unsigned int)down);
        if (atomic_cmpxchg(u.o, orig, val) != orig)
                goto repeat;
}

static inline void z_erofs_onlinepage_endio(struct page *page)
{
        union z_erofs_onlinepage_converter u;
        unsigned int v;

        DBG_BUGON(!PagePrivate(page));
        u.v = &page_private(page);

        v = atomic_dec_return(u.o);
        if (!(v & Z_EROFS_ONLINEPAGE_COUNT_MASK)) {
                set_page_private(page, 0);
                ClearPagePrivate(page);
                if (!PageError(page))
                        SetPageUptodate(page);
                unlock_page(page);
        }
        erofs_dbg("%s, page %p value %x", __func__, page, atomic_read(u.o));
}

#define Z_EROFS_VMAP_ONSTACK_PAGES      \
        min_t(unsigned int, THREAD_SIZE / 8 / sizeof(struct page *), 96U)
#define Z_EROFS_VMAP_GLOBAL_PAGES       2048

#endif