/*
 * fs/logfs/super.c
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
 *
 * Generally contains mount/umount code and also serves as a dump area for
 * any functions that don't fit elsewhere and neither justify a file of their
 * own.
 */
#include "logfs.h"
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/mtd/mtd.h>
#include <linux/statfs.h>
#include <linux/buffer_head.h>

static DEFINE_MUTEX(emergency_mutex);
static struct page *emergency_page;

struct page *emergency_read_begin(struct address_space *mapping, pgoff_t index)
{
        filler_t *filler = (filler_t *)mapping->a_ops->readpage;
        struct page *page;
        int err;

        page = read_cache_page(mapping, index, filler, NULL);
        if (page)
                return page;

        /* No more pages available, switch to emergency page */
        printk(KERN_INFO"Logfs: Using emergency page\n");
        mutex_lock(&emergency_mutex);
        err = filler(NULL, emergency_page);
        if (err) {
                mutex_unlock(&emergency_mutex);
                printk(KERN_EMERG"Logfs: Error reading emergency page\n");
                return ERR_PTR(err);
        }
        return emergency_page;
}

void emergency_read_end(struct page *page)
{
        if (page == emergency_page)
                mutex_unlock(&emergency_mutex);
        else
                page_cache_release(page);
}

static void dump_segfile(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);
        struct logfs_segment_entry se;
        u32 segno;

        for (segno = 0; segno < super->s_no_segs; segno++) {
                logfs_get_segment_entry(sb, segno, &se);
                printk("%3x: %6x %8x", segno, be32_to_cpu(se.ec_level),
                                be32_to_cpu(se.valid));
                if (++segno < super->s_no_segs) {
                        logfs_get_segment_entry(sb, segno, &se);
                        printk(" %6x %8x", be32_to_cpu(se.ec_level),
                                        be32_to_cpu(se.valid));
                }
                if (++segno < super->s_no_segs) {
                        logfs_get_segment_entry(sb, segno, &se);
                        printk(" %6x %8x", be32_to_cpu(se.ec_level),
                                        be32_to_cpu(se.valid));
                }
                if (++segno < super->s_no_segs) {
                        logfs_get_segment_entry(sb, segno, &se);
                        printk(" %6x %8x", be32_to_cpu(se.ec_level),
                                        be32_to_cpu(se.valid));
                }
                printk("\n");
        }
}

/*
 * logfs_crash_dump - dump debug information to device
 *
 * The LogFS superblock only occupies part of a segment.  This function will
 * write as much debug information as it can gather into the spare space.
 */
void logfs_crash_dump(struct super_block *sb)
{
        dump_segfile(sb);
}

/*
 * TODO: move to lib/string.c
 */
/**
 * memchr_inv - Find a character in an area of memory.
 * @s: The memory area
 * @c: The byte to search for
 * @n: The size of the area.
 *
 * returns the address of the first character other than @c, or %NULL
 * if the whole buffer contains just @c.
 */
void *memchr_inv(const void *s, int c, size_t n)
{
        const unsigned char *p = s;
        while (n-- != 0)
                if ((unsigned char)c != *p++)
                        return (void *)(p - 1);

        return NULL;
}

/*
 * FIXME: There should be a reserve for root, similar to ext2.
 */
int logfs_statfs(struct dentry *dentry, struct kstatfs *stats)
{
        struct super_block *sb = dentry->d_sb;
        struct logfs_super *super = logfs_super(sb);

        stats->f_type           = LOGFS_MAGIC_U32;
        stats->f_bsize          = sb->s_blocksize;
        stats->f_blocks         = super->s_size >> LOGFS_BLOCK_BITS >> 3;
        stats->f_bfree          = super->s_free_bytes >> sb->s_blocksize_bits;
        stats->f_bavail         = super->s_free_bytes >> sb->s_blocksize_bits;
        stats->f_files          = 0;
        stats->f_ffree          = 0;
        stats->f_namelen        = LOGFS_MAX_NAMELEN;
        return 0;
}

static int logfs_sb_set(struct super_block *sb, void *_super)
{
        struct logfs_super *super = _super;

        sb->s_fs_info = super;
        sb->s_mtd = super->s_mtd;
        sb->s_bdev = super->s_bdev;
#ifdef CONFIG_BLOCK
        if (sb->s_bdev)
                sb->s_bdi = &bdev_get_queue(sb->s_bdev)->backing_dev_info;
#endif
#ifdef CONFIG_MTD
        if (sb->s_mtd)
                sb->s_bdi = sb->s_mtd->backing_dev_info;
#endif
        return 0;
}

static int logfs_sb_test(struct super_block *sb, void *_super)
{
        struct logfs_super *super = _super;
        struct mtd_info *mtd = super->s_mtd;

        if (mtd && sb->s_mtd == mtd)
                return 1;
        if (super->s_bdev && sb->s_bdev == super->s_bdev)
                return 1;
        return 0;
}

static void set_segment_header(struct logfs_segment_header *sh, u8 type,
                u8 level, u32 segno, u32 ec)
{
        sh->pad = 0;
        sh->type = type;
        sh->level = level;
        sh->segno = cpu_to_be32(segno);
        sh->ec = cpu_to_be32(ec);
        sh->gec = cpu_to_be64(segno);
        sh->crc = logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4);
}

static void logfs_write_ds(struct super_block *sb, struct logfs_disk_super *ds,
                u32 segno, u32 ec)
{
        struct logfs_super *super = logfs_super(sb);
        struct logfs_segment_header *sh = &ds->ds_sh;
        int i;

        memset(ds, 0, sizeof(*ds));
        set_segment_header(sh, SEG_SUPER, 0, segno, ec);

        ds->ds_ifile_levels     = super->s_ifile_levels;
        ds->ds_iblock_levels    = super->s_iblock_levels;
        ds->ds_data_levels      = super->s_data_levels; /* XXX: Remove */
        ds->ds_segment_shift    = super->s_segshift;
        ds->ds_block_shift      = sb->s_blocksize_bits;
        ds->ds_write_shift      = super->s_writeshift;
        ds->ds_filesystem_size  = cpu_to_be64(super->s_size);
        ds->ds_segment_size     = cpu_to_be32(super->s_segsize);
        ds->ds_bad_seg_reserve  = cpu_to_be32(super->s_bad_seg_reserve);
        ds->ds_feature_incompat = cpu_to_be64(super->s_feature_incompat);
        ds->ds_feature_ro_compat= cpu_to_be64(super->s_feature_ro_compat);
        ds->ds_feature_compat   = cpu_to_be64(super->s_feature_compat);
        ds->ds_feature_flags    = cpu_to_be64(super->s_feature_flags);
        ds->ds_root_reserve     = cpu_to_be64(super->s_root_reserve);
        ds->ds_speed_reserve    = cpu_to_be64(super->s_speed_reserve);
        journal_for_each(i)
                ds->ds_journal_seg[i] = cpu_to_be32(super->s_journal_seg[i]);
        ds->ds_magic            = cpu_to_be64(LOGFS_MAGIC);
        ds->ds_crc = logfs_crc32(ds, sizeof(*ds),
                        LOGFS_SEGMENT_HEADERSIZE + 12);
}

static int write_one_sb(struct super_block *sb,
                struct page *(*find_sb)(struct super_block *sb, u64 *ofs))
{
        struct logfs_super *super = logfs_super(sb);
        struct logfs_disk_super *ds;
        struct logfs_segment_entry se;
        struct page *page;
        u64 ofs;
        u32 ec, segno;
        int err;

        page = find_sb(sb, &ofs);
        if (!page)
                return -EIO;
        ds = page_address(page);
        segno = seg_no(sb, ofs);
        logfs_get_segment_entry(sb, segno, &se);
        ec = be32_to_cpu(se.ec_level) >> 4;
        ec++;
        logfs_set_segment_erased(sb, segno, ec, 0);
        logfs_write_ds(sb, ds, segno, ec);
        err = super->s_devops->write_sb(sb, page);
        page_cache_release(page);
        return err;
}

int logfs_write_sb(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);
        int err;

        /* First superblock */
        err = write_one_sb(sb, super->s_devops->find_first_sb);
        if (err)
                return err;

        /* Last superblock */
        err = write_one_sb(sb, super->s_devops->find_last_sb);
        if (err)
                return err;
        return 0;
}

static int ds_cmp(const void *ds0, const void *ds1)
{
        size_t len = sizeof(struct logfs_disk_super);

        /* We know the segment headers differ, so ignore them */
        len -= LOGFS_SEGMENT_HEADERSIZE;
        ds0 += LOGFS_SEGMENT_HEADERSIZE;
        ds1 += LOGFS_SEGMENT_HEADERSIZE;
        return memcmp(ds0, ds1, len);
}

static int logfs_recover_sb(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);
        struct logfs_disk_super _ds0, *ds0 = &_ds0;
        struct logfs_disk_super _ds1, *ds1 = &_ds1;
        int err, valid0, valid1;

        /* read first superblock */
        err = wbuf_read(sb, super->s_sb_ofs[0], sizeof(*ds0), ds0);
        if (err)
                return err;
        /* read last superblock */
        err = wbuf_read(sb, super->s_sb_ofs[1], sizeof(*ds1), ds1);
        if (err)
                return err;
        valid0 = logfs_check_ds(ds0) == 0;
        valid1 = logfs_check_ds(ds1) == 0;

        if (!valid0 && valid1) {
                printk(KERN_INFO"First superblock is invalid - fixing.\n");
                return write_one_sb(sb, super->s_devops->find_first_sb);
        }
        if (valid0 && !valid1) {
                printk(KERN_INFO"Last superblock is invalid - fixing.\n");
                return write_one_sb(sb, super->s_devops->find_last_sb);
        }
        if (valid0 && valid1 && ds_cmp(ds0, ds1)) {
                printk(KERN_INFO"Superblocks don't match - fixing.\n");
                return logfs_write_sb(sb);
        }
        /* If neither is valid now, something's wrong.  Didn't we properly
         * check them before?!? */
        BUG_ON(!valid0 && !valid1);
        return 0;
}

static int logfs_make_writeable(struct super_block *sb)
{
        int err;

        err = logfs_open_segfile(sb);
        if (err)
                return err;

        /* Repair any broken superblock copies */
        err = logfs_recover_sb(sb);
        if (err)
                return err;

        /* Check areas for trailing unaccounted data */
        err = logfs_check_areas(sb);
        if (err)
                return err;

        /* Do one GC pass before any data gets dirtied */
        logfs_gc_pass(sb);

        /* after all initializations are done, replay the journal
         * for rw-mounts, if necessary */
        err = logfs_replay_journal(sb);
        if (err)
                return err;

        return 0;
}

static int logfs_get_sb_final(struct super_block *sb, struct vfsmount *mnt)
{
        struct logfs_super *super = logfs_super(sb);
        struct inode *rootdir;
        int err;

        /* root dir */
        rootdir = logfs_iget(sb, LOGFS_INO_ROOT);
        if (IS_ERR(rootdir))
                goto fail;

        sb->s_root = d_alloc_root(rootdir);
        if (!sb->s_root) {
                iput(rootdir);
                goto fail;
        }

        super->s_erase_page = alloc_pages(GFP_KERNEL, 0);
        if (!super->s_erase_page)
                goto fail;
        memset(page_address(super->s_erase_page), 0xFF, PAGE_SIZE);

        /* FIXME: check for read-only mounts */
        err = logfs_make_writeable(sb);
        if (err)
                goto fail1;

        log_super("LogFS: Finished mounting\n");
        simple_set_mnt(mnt, sb);
        return 0;

fail1:
        __free_page(super->s_erase_page);
fail:
        iput(logfs_super(sb)->s_master_inode);
        return -EIO;
}

int logfs_check_ds(struct logfs_disk_super *ds)
{
        struct logfs_segment_header *sh = &ds->ds_sh;

        if (ds->ds_magic != cpu_to_be64(LOGFS_MAGIC))
                return -EINVAL;
        if (sh->crc != logfs_crc32(sh, LOGFS_SEGMENT_HEADERSIZE, 4))
                return -EINVAL;
        if (ds->ds_crc != logfs_crc32(ds, sizeof(*ds),
                                LOGFS_SEGMENT_HEADERSIZE + 12))
                return -EINVAL;
        return 0;
}

static struct page *find_super_block(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);
        struct page *first, *last;

        first = super->s_devops->find_first_sb(sb, &super->s_sb_ofs[0]);
        if (!first || IS_ERR(first))
                return NULL;
        last = super->s_devops->find_last_sb(sb, &super->s_sb_ofs[1]);
        if (!last || IS_ERR(last)) {
                page_cache_release(first);
                return NULL;
        }

        if (!logfs_check_ds(page_address(first))) {
                page_cache_release(last);
                return first;
        }

        /* First one didn't work, try the second superblock */
        if (!logfs_check_ds(page_address(last))) {
                page_cache_release(first);
                return last;
        }

        /* Neither worked, sorry folks */
        page_cache_release(first);
        page_cache_release(last);
        return NULL;
}

static int __logfs_read_sb(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);
        struct page *page;
        struct logfs_disk_super *ds;
        int i;

        page = find_super_block(sb);
        if (!page)
                return -EINVAL;

        ds = page_address(page);
        super->s_size = be64_to_cpu(ds->ds_filesystem_size);
        super->s_root_reserve = be64_to_cpu(ds->ds_root_reserve);
        super->s_speed_reserve = be64_to_cpu(ds->ds_speed_reserve);
        super->s_bad_seg_reserve = be32_to_cpu(ds->ds_bad_seg_reserve);
        super->s_segsize = 1 << ds->ds_segment_shift;
        super->s_segmask = (1 << ds->ds_segment_shift) - 1;
        super->s_segshift = ds->ds_segment_shift;
        sb->s_blocksize = 1 << ds->ds_block_shift;
        sb->s_blocksize_bits = ds->ds_block_shift;
        super->s_writesize = 1 << ds->ds_write_shift;
        super->s_writeshift = ds->ds_write_shift;
        super->s_no_segs = super->s_size >> super->s_segshift;
        super->s_no_blocks = super->s_segsize >> sb->s_blocksize_bits;
        super->s_feature_incompat = be64_to_cpu(ds->ds_feature_incompat);
        super->s_feature_ro_compat = be64_to_cpu(ds->ds_feature_ro_compat);
        super->s_feature_compat = be64_to_cpu(ds->ds_feature_compat);
        super->s_feature_flags = be64_to_cpu(ds->ds_feature_flags);

        journal_for_each(i)
                super->s_journal_seg[i] = be32_to_cpu(ds->ds_journal_seg[i]);

        super->s_ifile_levels = ds->ds_ifile_levels;
        super->s_iblock_levels = ds->ds_iblock_levels;
        super->s_data_levels = ds->ds_data_levels;
        super->s_total_levels = super->s_ifile_levels + super->s_iblock_levels
                + super->s_data_levels;
        page_cache_release(page);
        return 0;
}

static int logfs_read_sb(struct super_block *sb, int read_only)
{
        struct logfs_super *super = logfs_super(sb);
        int ret;

        super->s_btree_pool = mempool_create(32, btree_alloc, btree_free, NULL);
        if (!super->s_btree_pool)
                return -ENOMEM;

        btree_init_mempool64(&super->s_shadow_tree.new, super->s_btree_pool);
        btree_init_mempool64(&super->s_shadow_tree.old, super->s_btree_pool);
        btree_init_mempool32(&super->s_shadow_tree.segment_map,
                        super->s_btree_pool);

        ret = logfs_init_mapping(sb);
        if (ret)
                return ret;

        ret = __logfs_read_sb(sb);
        if (ret)
                return ret;

        if (super->s_feature_incompat & ~LOGFS_FEATURES_INCOMPAT)
                return -EIO;
        if ((super->s_feature_ro_compat & ~LOGFS_FEATURES_RO_COMPAT) &&
                        !read_only)
                return -EIO;

        mutex_init(&super->s_dirop_mutex);
        mutex_init(&super->s_object_alias_mutex);
        INIT_LIST_HEAD(&super->s_freeing_list);

        ret = logfs_init_rw(sb);
        if (ret)
                return ret;

        ret = logfs_init_areas(sb);
        if (ret)
                return ret;

        ret = logfs_init_gc(sb);
        if (ret)
                return ret;

        ret = logfs_init_journal(sb);
        if (ret)
                return ret;

        return 0;
}

static void logfs_kill_sb(struct super_block *sb)
{
        struct logfs_super *super = logfs_super(sb);

        log_super("LogFS: Start unmounting\n");
        /* Alias entries slow down mount, so evict as many as possible */
        sync_filesystem(sb);
        logfs_write_anchor(sb);

        /*
         * From this point on alias entries are simply dropped - and any
         * writes to the object store are considered bugs.
         */
        super->s_flags |= LOGFS_SB_FLAG_SHUTDOWN;
        log_super("LogFS: Now in shutdown\n");
        generic_shutdown_super(sb);

        BUG_ON(super->s_dirty_used_bytes || super->s_dirty_free_bytes);

        logfs_cleanup_gc(sb);
        logfs_cleanup_journal(sb);
        logfs_cleanup_areas(sb);
        logfs_cleanup_rw(sb);
        if (super->s_erase_page)
                __free_page(super->s_erase_page);
        super->s_devops->put_device(sb);
        logfs_mempool_destroy(super->s_btree_pool);
        logfs_mempool_destroy(super->s_alias_pool);
        kfree(super);
        log_super("LogFS: Finished unmounting\n");
}

int logfs_get_sb_device(struct file_system_type *type, int flags,
                struct mtd_info *mtd, struct block_device *bdev,
                const struct logfs_device_ops *devops, struct vfsmount *mnt)
{
        struct logfs_super *super;
        struct super_block *sb;
        int err = -ENOMEM;
        static int mount_count;

        log_super("LogFS: Start mount %x\n", mount_count++);
        super = kzalloc(sizeof(*super), GFP_KERNEL);
        if (!super)
                goto err0;

        super->s_mtd    = mtd;
        super->s_bdev   = bdev;
        err = -EINVAL;
        sb = sget(type, logfs_sb_test, logfs_sb_set, super);
        if (IS_ERR(sb))
                goto err0;

        if (sb->s_root) {
                /* Device is already in use */
                err = 0;
                simple_set_mnt(mnt, sb);
                goto err0;
        }

        super->s_devops = devops;

        /*
         * sb->s_maxbytes is limited to 8TB.  On 32bit systems, the page cache
         * only covers 16TB and the upper 8TB are used for indirect blocks.
         * On 64bit system we could bump up the limit, but that would make
         * the filesystem incompatible with 32bit systems.
         */
        sb->s_maxbytes  = (1ull << 43) - 1;
        sb->s_op        = &logfs_super_operations;
        sb->s_flags     = flags | MS_NOATIME;

        err = logfs_read_sb(sb, sb->s_flags & MS_RDONLY);
        if (err)
                goto err1;

        sb->s_flags |= MS_ACTIVE;
        err = logfs_get_sb_final(sb, mnt);
        if (err)
                goto err1;
        return 0;

err1:
        deactivate_locked_super(sb);
        return err;
err0:
        kfree(super);
        //devops->put_device(sb);
        return err;
}

static int logfs_get_sb(struct file_system_type *type, int flags,
                const char *devname, void *data, struct vfsmount *mnt)
{
        ulong mtdnr;

        if (!devname)
                return logfs_get_sb_bdev(type, flags, devname, mnt);
        if (strncmp(devname, "mtd", 3))
                return logfs_get_sb_bdev(type, flags, devname, mnt);

        {
                char *garbage;
                mtdnr = simple_strtoul(devname+3, &garbage, 0);
                if (*garbage)
                        return -EINVAL;
        }

        return logfs_get_sb_mtd(type, flags, mtdnr, mnt);
}

static struct file_system_type logfs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "logfs",
        .get_sb         = logfs_get_sb,
        .kill_sb        = logfs_kill_sb,
        .fs_flags       = FS_REQUIRES_DEV,

};

static int __init logfs_init(void)
{
        int ret;

        emergency_page = alloc_pages(GFP_KERNEL, 0);
        if (!emergency_page)
                return -ENOMEM;

        ret = logfs_compr_init();
        if (ret)
                goto out1;

        ret = logfs_init_inode_cache();
        if (ret)
                goto out2;

        return register_filesystem(&logfs_fs_type);
out2:
        logfs_compr_exit();
out1:
        __free_pages(emergency_page, 0);
        return ret;
}

static void __exit logfs_exit(void)
{
        unregister_filesystem(&logfs_fs_type);
        logfs_destroy_inode_cache();
        logfs_compr_exit();
        __free_pages(emergency_page, 0);
}

module_init(logfs_init);
module_exit(logfs_exit);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Joern Engel <joern@logfs.org>");
MODULE_DESCRIPTION("scalable flash filesystem");