// SPDX-License-Identifier: GPL-2.0-only
/*
 *      fs/bfs/inode.c
 *      BFS superblock and inode operations.
 *      Copyright (C) 1999-2018 Tigran Aivazian <aivazian.tigran@gmail.com>
 *      From fs/minix, Copyright (C) 1991, 1992 Linus Torvalds.
 *      Made endianness-clean by Andrew Stribblehill <ads@wompom.org>, 2005.
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/vfs.h>
#include <linux/writeback.h>
#include <linux/uio.h>
#include <linux/uaccess.h>
#include <linux/fs_context.h>
#include "bfs.h"

MODULE_AUTHOR("Tigran Aivazian <aivazian.tigran@gmail.com>");
MODULE_DESCRIPTION("SCO UnixWare BFS filesystem for Linux");
MODULE_LICENSE("GPL");

#undef DEBUG

#ifdef DEBUG
#define dprintf(x...)   printf(x)
#else
#define dprintf(x...)
#endif

struct inode *bfs_iget(struct super_block *sb, unsigned long ino)
{
        struct bfs_inode *di;
        struct inode *inode;
        struct buffer_head *bh;
        int block, off;

        inode = iget_locked(sb, ino);
        if (!inode)
                return ERR_PTR(-ENOMEM);
        if (!(inode_state_read_once(inode) & I_NEW))
                return inode;

        if ((ino < BFS_ROOT_INO) || (ino > BFS_SB(inode->i_sb)->si_lasti)) {
                printf("Bad inode number %s:%08lx\n", inode->i_sb->s_id, ino);
                goto error;
        }

        block = (ino - BFS_ROOT_INO) / BFS_INODES_PER_BLOCK + 1;
        bh = sb_bread(inode->i_sb, block);
        if (!bh) {
                printf("Unable to read inode %s:%08lx\n", inode->i_sb->s_id,
                                                                        ino);
                goto error;
        }

        off = (ino - BFS_ROOT_INO) % BFS_INODES_PER_BLOCK;
        di = (struct bfs_inode *)bh->b_data + off;

        /*
         * https://martin.hinner.info/fs/bfs/bfs-structure.html explains that
         * BFS in SCO UnixWare environment used only lower 9 bits of di->i_mode
         * value. This means that, although bfs_write_inode() saves whole
         * inode->i_mode bits (which include S_IFMT bits and S_IS{UID,GID,VTX}
         * bits), middle 7 bits of di->i_mode value can be garbage when these
         * bits were not saved by bfs_write_inode().
         * Since we can't tell whether middle 7 bits are garbage, use only
         * lower 12 bits (i.e. tolerate S_IS{UID,GID,VTX} bits possibly being
         * garbage) and reconstruct S_IFMT bits for Linux environment from
         * di->i_vtype value.
         */
        inode->i_mode = 0x00000FFF & le32_to_cpu(di->i_mode);
        if (le32_to_cpu(di->i_vtype) == BFS_VDIR) {
                inode->i_mode |= S_IFDIR;
                inode->i_op = &bfs_dir_inops;
                inode->i_fop = &bfs_dir_operations;
        } else if (le32_to_cpu(di->i_vtype) == BFS_VREG) {
                inode->i_mode |= S_IFREG;
                inode->i_op = &bfs_file_inops;
                inode->i_fop = &bfs_file_operations;
                inode->i_mapping->a_ops = &bfs_aops;
        } else {
                brelse(bh);
                printf("Unknown vtype=%u %s:%08lx\n",
                       le32_to_cpu(di->i_vtype), inode->i_sb->s_id, ino);
                goto error;
        }

        BFS_I(inode)->i_sblock =  le32_to_cpu(di->i_sblock);
        BFS_I(inode)->i_eblock =  le32_to_cpu(di->i_eblock);
        BFS_I(inode)->i_dsk_ino = le16_to_cpu(di->i_ino);
        i_uid_write(inode, le32_to_cpu(di->i_uid));
        i_gid_write(inode,  le32_to_cpu(di->i_gid));
        set_nlink(inode, le32_to_cpu(di->i_nlink));
        inode->i_size = BFS_FILESIZE(di);
        inode->i_blocks = BFS_FILEBLOCKS(di);
        inode_set_atime(inode, le32_to_cpu(di->i_atime), 0);
        inode_set_mtime(inode, le32_to_cpu(di->i_mtime), 0);
        inode_set_ctime(inode, le32_to_cpu(di->i_ctime), 0);

        brelse(bh);
        unlock_new_inode(inode);
        return inode;

error:
        iget_failed(inode);
        return ERR_PTR(-EIO);
}

static struct bfs_inode *find_inode(struct super_block *sb, u16 ino, struct buffer_head **p)
{
        if ((ino < BFS_ROOT_INO) || (ino > BFS_SB(sb)->si_lasti)) {
                printf("Bad inode number %s:%08x\n", sb->s_id, ino);
                return ERR_PTR(-EIO);
        }

        ino -= BFS_ROOT_INO;

        *p = sb_bread(sb, 1 + ino / BFS_INODES_PER_BLOCK);
        if (!*p) {
                printf("Unable to read inode %s:%08x\n", sb->s_id, ino);
                return ERR_PTR(-EIO);
        }

        return (struct bfs_inode *)(*p)->b_data +  ino % BFS_INODES_PER_BLOCK;
}

static int bfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        struct bfs_sb_info *info = BFS_SB(inode->i_sb);
        unsigned int ino = (u16)inode->i_ino;
        unsigned long i_sblock;
        struct bfs_inode *di;
        struct buffer_head *bh;
        int err = 0;

        dprintf("ino=%08x\n", ino);

        di = find_inode(inode->i_sb, ino, &bh);
        if (IS_ERR(di))
                return PTR_ERR(di);

        mutex_lock(&info->bfs_lock);

        if (ino == BFS_ROOT_INO)
                di->i_vtype = cpu_to_le32(BFS_VDIR);
        else
                di->i_vtype = cpu_to_le32(BFS_VREG);

        di->i_ino = cpu_to_le16(ino);
        di->i_mode = cpu_to_le32(inode->i_mode);
        di->i_uid = cpu_to_le32(i_uid_read(inode));
        di->i_gid = cpu_to_le32(i_gid_read(inode));
        di->i_nlink = cpu_to_le32(inode->i_nlink);
        di->i_atime = cpu_to_le32(inode_get_atime_sec(inode));
        di->i_mtime = cpu_to_le32(inode_get_mtime_sec(inode));
        di->i_ctime = cpu_to_le32(inode_get_ctime_sec(inode));
        i_sblock = BFS_I(inode)->i_sblock;
        di->i_sblock = cpu_to_le32(i_sblock);
        di->i_eblock = cpu_to_le32(BFS_I(inode)->i_eblock);
        di->i_eoffset = cpu_to_le32(i_sblock * BFS_BSIZE + inode->i_size - 1);

        mark_buffer_dirty(bh);
        if (wbc->sync_mode == WB_SYNC_ALL) {
                sync_dirty_buffer(bh);
                if (buffer_req(bh) && !buffer_uptodate(bh))
                        err = -EIO;
        }
        brelse(bh);
        mutex_unlock(&info->bfs_lock);
        return err;
}

static void bfs_evict_inode(struct inode *inode)
{
        unsigned long ino = inode->i_ino;
        struct bfs_inode *di;
        struct buffer_head *bh;
        struct super_block *s = inode->i_sb;
        struct bfs_sb_info *info = BFS_SB(s);
        struct bfs_inode_info *bi = BFS_I(inode);

        dprintf("ino=%08lx\n", ino);

        truncate_inode_pages_final(&inode->i_data);
        invalidate_inode_buffers(inode);
        clear_inode(inode);

        if (inode->i_nlink)
                return;

        di = find_inode(s, inode->i_ino, &bh);
        if (IS_ERR(di))
                return;

        mutex_lock(&info->bfs_lock);
        /* clear on-disk inode */
        memset(di, 0, sizeof(struct bfs_inode));
        mark_buffer_dirty(bh);
        brelse(bh);

        if (bi->i_dsk_ino) {
                if (bi->i_sblock)
                        info->si_freeb += bi->i_eblock + 1 - bi->i_sblock;
                info->si_freei++;
                clear_bit(ino, info->si_imap);
                bfs_dump_imap("evict_inode", s);
        }

        /*
         * If this was the last file, make the previous block
         * "last block of the last file" even if there is no
         * real file there, saves us 1 gap.
         */
        if (info->si_lf_eblk == bi->i_eblock)
                info->si_lf_eblk = bi->i_sblock - 1;
        mutex_unlock(&info->bfs_lock);
}

static void bfs_put_super(struct super_block *s)
{
        struct bfs_sb_info *info = BFS_SB(s);

        if (!info)
                return;

        mutex_destroy(&info->bfs_lock);
        kfree(info);
        s->s_fs_info = NULL;
}

static int bfs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *s = dentry->d_sb;
        struct bfs_sb_info *info = BFS_SB(s);
        u64 id = huge_encode_dev(s->s_bdev->bd_dev);
        buf->f_type = BFS_MAGIC;
        buf->f_bsize = s->s_blocksize;
        buf->f_blocks = info->si_blocks;
        buf->f_bfree = buf->f_bavail = info->si_freeb;
        buf->f_files = info->si_lasti + 1 - BFS_ROOT_INO;
        buf->f_ffree = info->si_freei;
        buf->f_fsid = u64_to_fsid(id);
        buf->f_namelen = BFS_NAMELEN;
        return 0;
}

static struct kmem_cache *bfs_inode_cachep;

static struct inode *bfs_alloc_inode(struct super_block *sb)
{
        struct bfs_inode_info *bi;
        bi = alloc_inode_sb(sb, bfs_inode_cachep, GFP_KERNEL);
        if (!bi)
                return NULL;
        return &bi->vfs_inode;
}

static void bfs_free_inode(struct inode *inode)
{
        kmem_cache_free(bfs_inode_cachep, BFS_I(inode));
}

static void init_once(void *foo)
{
        struct bfs_inode_info *bi = foo;

        inode_init_once(&bi->vfs_inode);
}

static int __init init_inodecache(void)
{
        bfs_inode_cachep = kmem_cache_create("bfs_inode_cache",
                                             sizeof(struct bfs_inode_info),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_ACCOUNT),
                                             init_once);
        if (bfs_inode_cachep == NULL)
                return -ENOMEM;
        return 0;
}

static void destroy_inodecache(void)
{
        /*
         * Make sure all delayed rcu free inodes are flushed before we
         * destroy cache.
         */
        rcu_barrier();
        kmem_cache_destroy(bfs_inode_cachep);
}

static const struct super_operations bfs_sops = {
        .alloc_inode    = bfs_alloc_inode,
        .free_inode     = bfs_free_inode,
        .write_inode    = bfs_write_inode,
        .evict_inode    = bfs_evict_inode,
        .put_super      = bfs_put_super,
        .statfs         = bfs_statfs,
};

void bfs_dump_imap(const char *prefix, struct super_block *s)
{
#ifdef DEBUG
        int i;
        char *tmpbuf = (char *)get_zeroed_page(GFP_KERNEL);

        if (!tmpbuf)
                return;
        for (i = BFS_SB(s)->si_lasti; i >= 0; i--) {
                if (i > PAGE_SIZE - 100) break;
                if (test_bit(i, BFS_SB(s)->si_imap))
                        strcat(tmpbuf, "1");
                else
                        strcat(tmpbuf, "0");
        }
        printf("%s: lasti=%08lx <%s>\n", prefix, BFS_SB(s)->si_lasti, tmpbuf);
        free_page((unsigned long)tmpbuf);
#endif
}

static int bfs_fill_super(struct super_block *s, struct fs_context *fc)
{
        struct buffer_head *bh, *sbh;
        struct bfs_super_block *bfs_sb;
        struct inode *inode;
        unsigned i;
        struct bfs_sb_info *info;
        int ret = -EINVAL;
        unsigned long i_sblock, i_eblock, i_eoff, s_size;
        int silent = fc->sb_flags & SB_SILENT;

        info = kzalloc_obj(*info);
        if (!info)
                return -ENOMEM;
        mutex_init(&info->bfs_lock);
        s->s_fs_info = info;
        s->s_time_min = 0;
        s->s_time_max = U32_MAX;

        sb_set_blocksize(s, BFS_BSIZE);

        sbh = sb_bread(s, 0);
        if (!sbh)
                goto out;
        bfs_sb = (struct bfs_super_block *)sbh->b_data;
        if (le32_to_cpu(bfs_sb->s_magic) != BFS_MAGIC) {
                if (!silent)
                        printf("No BFS filesystem on %s (magic=%08x)\n", s->s_id,  le32_to_cpu(bfs_sb->s_magic));
                goto out1;
        }
        if (BFS_UNCLEAN(bfs_sb, s) && !silent)
                printf("%s is unclean, continuing\n", s->s_id);

        s->s_magic = BFS_MAGIC;

        if (le32_to_cpu(bfs_sb->s_start) > le32_to_cpu(bfs_sb->s_end) ||
            le32_to_cpu(bfs_sb->s_start) < sizeof(struct bfs_super_block) + sizeof(struct bfs_dirent)) {
                printf("Superblock is corrupted on %s\n", s->s_id);
                goto out1;
        }

        info->si_lasti = (le32_to_cpu(bfs_sb->s_start) - BFS_BSIZE) / sizeof(struct bfs_inode) + BFS_ROOT_INO - 1;
        if (info->si_lasti == BFS_MAX_LASTI)
                printf("NOTE: filesystem %s was created with 512 inodes, the real maximum is 511, mounting anyway\n", s->s_id);
        else if (info->si_lasti > BFS_MAX_LASTI) {
                printf("Impossible last inode number %lu > %d on %s\n", info->si_lasti, BFS_MAX_LASTI, s->s_id);
                goto out1;
        }
        for (i = 0; i < BFS_ROOT_INO; i++)
                set_bit(i, info->si_imap);

        s->s_op = &bfs_sops;
        inode = bfs_iget(s, BFS_ROOT_INO);
        if (IS_ERR(inode)) {
                ret = PTR_ERR(inode);
                goto out1;
        }
        s->s_root = d_make_root(inode);
        if (!s->s_root) {
                ret = -ENOMEM;
                goto out1;
        }

        info->si_blocks = (le32_to_cpu(bfs_sb->s_end) + 1) >> BFS_BSIZE_BITS;
        info->si_freeb = (le32_to_cpu(bfs_sb->s_end) + 1 - le32_to_cpu(bfs_sb->s_start)) >> BFS_BSIZE_BITS;
        info->si_freei = 0;
        info->si_lf_eblk = 0;

        /* can we read the last block? */
        bh = sb_bread(s, info->si_blocks - 1);
        if (!bh) {
                printf("Last block not available on %s: %lu\n", s->s_id, info->si_blocks - 1);
                ret = -EIO;
                goto out2;
        }
        brelse(bh);

        bh = NULL;
        for (i = BFS_ROOT_INO; i <= info->si_lasti; i++) {
                struct bfs_inode *di;
                int block = (i - BFS_ROOT_INO) / BFS_INODES_PER_BLOCK + 1;
                int off = (i - BFS_ROOT_INO) % BFS_INODES_PER_BLOCK;
                unsigned long eblock;

                if (!off) {
                        brelse(bh);
                        bh = sb_bread(s, block);
                }

                if (!bh)
                        continue;

                di = (struct bfs_inode *)bh->b_data + off;

                /* test if filesystem is not corrupted */

                i_eoff = le32_to_cpu(di->i_eoffset);
                i_sblock = le32_to_cpu(di->i_sblock);
                i_eblock = le32_to_cpu(di->i_eblock);
                s_size = le32_to_cpu(bfs_sb->s_end);

                if (i_sblock > info->si_blocks ||
                        i_eblock > info->si_blocks ||
                        i_sblock > i_eblock ||
                        (i_eoff != le32_to_cpu(-1) && i_eoff > s_size) ||
                        i_sblock * BFS_BSIZE > i_eoff) {

                        printf("Inode 0x%08x corrupted on %s\n", i, s->s_id);

                        brelse(bh);
                        ret = -EIO;
                        goto out2;
                }

                if (!di->i_ino) {
                        info->si_freei++;
                        continue;
                }
                set_bit(i, info->si_imap);
                info->si_freeb -= BFS_FILEBLOCKS(di);

                eblock =  le32_to_cpu(di->i_eblock);
                if (eblock > info->si_lf_eblk)
                        info->si_lf_eblk = eblock;
        }
        brelse(bh);
        brelse(sbh);
        bfs_dump_imap("fill_super", s);
        return 0;

out2:
        dput(s->s_root);
        s->s_root = NULL;
out1:
        brelse(sbh);
out:
        mutex_destroy(&info->bfs_lock);
        kfree(info);
        s->s_fs_info = NULL;
        return ret;
}

static int bfs_get_tree(struct fs_context *fc)
{
        return get_tree_bdev(fc, bfs_fill_super);
}

static const struct fs_context_operations bfs_context_ops = {
        .get_tree = bfs_get_tree,
};

static int bfs_init_fs_context(struct fs_context *fc)
{
        fc->ops = &bfs_context_ops;

        return 0;
}

static struct file_system_type bfs_fs_type = {
        .owner                  = THIS_MODULE,
        .name                   = "bfs",
        .init_fs_context        = bfs_init_fs_context,
        .kill_sb                = kill_block_super,
        .fs_flags               = FS_REQUIRES_DEV,
};
MODULE_ALIAS_FS("bfs");

static int __init init_bfs_fs(void)
{
        int err = init_inodecache();
        if (err)
                goto out1;
        err = register_filesystem(&bfs_fs_type);
        if (err)
                goto out;
        return 0;
out:
        destroy_inodecache();
out1:
        return err;
}

static void __exit exit_bfs_fs(void)
{
        unregister_filesystem(&bfs_fs_type);
        destroy_inodecache();
}

module_init(init_bfs_fs)
module_exit(exit_bfs_fs)