// SPDX-License-Identifier: GPL-2.0-only
/*
 * QNX4 file system, Linux implementation.
 *
 * Version : 0.2.1
 *
 * Using parts of the xiafs filesystem.
 *
 * History :
 *
 * 01-06-1998 by Richard Frowijn : first release.
 * 20-06-1998 by Frank Denis : Linux 2.1.99+ support, boot signature, misc.
 * 30-06-1998 by Frank Denis : first step to write inodes.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/fs_context.h>
#include "qnx4.h"

#define QNX4_VERSION  4
#define QNX4_BMNAME   ".bitmap"

static const struct super_operations qnx4_sops;

static struct inode *qnx4_alloc_inode(struct super_block *sb);
static void qnx4_free_inode(struct inode *inode);
static int qnx4_statfs(struct dentry *, struct kstatfs *);
static int qnx4_get_tree(struct fs_context *fc);

static const struct super_operations qnx4_sops =
{
        .alloc_inode    = qnx4_alloc_inode,
        .free_inode     = qnx4_free_inode,
        .statfs         = qnx4_statfs,
};

static int qnx4_reconfigure(struct fs_context *fc)
{
        struct super_block *sb = fc->root->d_sb;
        struct qnx4_sb_info *qs;

        sync_filesystem(sb);
        qs = qnx4_sb(sb);
        qs->Version = QNX4_VERSION;
        fc->sb_flags |= SB_RDONLY;
        return 0;
}

static const struct fs_context_operations qnx4_context_opts = {
        .get_tree       = qnx4_get_tree,
        .reconfigure    = qnx4_reconfigure,
};

static int qnx4_get_block( struct inode *inode, sector_t iblock, struct buffer_head *bh, int create )
{
        unsigned long phys;

        QNX4DEBUG((KERN_INFO "qnx4: qnx4_get_block inode=[%ld] iblock=[%ld]\n",inode->i_ino,iblock));

        phys = qnx4_block_map( inode, iblock );
        if ( phys ) {
                // logical block is before EOF
                map_bh(bh, inode->i_sb, phys);
        }
        return 0;
}

static inline u32 try_extent(qnx4_xtnt_t *extent, u32 *offset)
{
        u32 size = le32_to_cpu(extent->xtnt_size);
        if (*offset < size)
                return le32_to_cpu(extent->xtnt_blk) + *offset - 1;
        *offset -= size;
        return 0;
}

unsigned long qnx4_block_map( struct inode *inode, long iblock )
{
        int ix;
        long i_xblk;
        struct buffer_head *bh = NULL;
        struct qnx4_xblk *xblk = NULL;
        struct qnx4_inode_entry *qnx4_inode = qnx4_raw_inode(inode);
        u16 nxtnt = le16_to_cpu(qnx4_inode->di_num_xtnts);
        u32 offset = iblock;
        u32 block = try_extent(&qnx4_inode->di_first_xtnt, &offset);

        if (block) {
                // iblock is in the first extent. This is easy.
        } else {
                // iblock is beyond first extent. We have to follow the extent chain.
                i_xblk = le32_to_cpu(qnx4_inode->di_xblk);
                ix = 0;
                while ( --nxtnt > 0 ) {
                        if ( ix == 0 ) {
                                // read next xtnt block.
                                bh = sb_bread(inode->i_sb, i_xblk - 1);
                                if ( !bh ) {
                                        QNX4DEBUG((KERN_ERR "qnx4: I/O error reading xtnt block [%ld])\n", i_xblk - 1));
                                        return -EIO;
                                }
                                xblk = (struct qnx4_xblk*)bh->b_data;
                                if ( memcmp( xblk->xblk_signature, "IamXblk", 7 ) ) {
                                        QNX4DEBUG((KERN_ERR "qnx4: block at %ld is not a valid xtnt\n", qnx4_inode->i_xblk));
                                        return -EIO;
                                }
                        }
                        block = try_extent(&xblk->xblk_xtnts[ix], &offset);
                        if (block) {
                                // got it!
                                break;
                        }
                        if ( ++ix >= xblk->xblk_num_xtnts ) {
                                i_xblk = le32_to_cpu(xblk->xblk_next_xblk);
                                ix = 0;
                                brelse( bh );
                                bh = NULL;
                        }
                }
                if ( bh )
                        brelse( bh );
        }

        QNX4DEBUG((KERN_INFO "qnx4: mapping block %ld of inode %ld = %ld\n",iblock,inode->i_ino,block));
        return block;
}

static int qnx4_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        u64 id = huge_encode_dev(sb->s_bdev->bd_dev);

        buf->f_type    = sb->s_magic;
        buf->f_bsize   = sb->s_blocksize;
        buf->f_blocks  = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size) * 8;
        buf->f_bfree   = qnx4_count_free_blocks(sb);
        buf->f_bavail  = buf->f_bfree;
        buf->f_namelen = QNX4_NAME_MAX;
        buf->f_fsid    = u64_to_fsid(id);

        return 0;
}

/*
 * Check the root directory of the filesystem to make sure
 * it really _is_ a qnx4 filesystem, and to check the size
 * of the directory entry.
 */
static const char *qnx4_checkroot(struct super_block *sb,
                                  struct qnx4_super_block *s)
{
        struct buffer_head *bh;
        struct qnx4_inode_entry *rootdir;
        int rd, rl;
        int i, j;

        if (s->RootDir.di_fname[0] != '/' || s->RootDir.di_fname[1] != '\0')
                return "no qnx4 filesystem (no root dir).";
        QNX4DEBUG((KERN_NOTICE "QNX4 filesystem found on dev %s.\n", sb->s_id));
        rd = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_blk) - 1;
        rl = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_size);
        for (j = 0; j < rl; j++) {
                bh = sb_bread(sb, rd + j);      /* root dir, first block */
                if (bh == NULL)
                        return "unable to read root entry.";
                rootdir = (struct qnx4_inode_entry *) bh->b_data;
                for (i = 0; i < QNX4_INODES_PER_BLOCK; i++, rootdir++) {
                        QNX4DEBUG((KERN_INFO "rootdir entry found : [%s]\n", rootdir->di_fname));
                        if (strcmp(rootdir->di_fname, QNX4_BMNAME) != 0)
                                continue;
                        qnx4_sb(sb)->BitMap = kmemdup(rootdir,
                                                      sizeof(struct qnx4_inode_entry),
                                                      GFP_KERNEL);
                        brelse(bh);
                        if (!qnx4_sb(sb)->BitMap)
                                return "not enough memory for bitmap inode";
                        /* keep bitmap inode known */
                        return NULL;
                }
                brelse(bh);
        }
        return "bitmap file not found.";
}

static int qnx4_fill_super(struct super_block *s, struct fs_context *fc)
{
        struct buffer_head *bh;
        struct inode *root;
        const char *errmsg;
        struct qnx4_sb_info *qs;
        int silent = fc->sb_flags & SB_SILENT;

        qs = kzalloc_obj(struct qnx4_sb_info);
        if (!qs)
                return -ENOMEM;
        s->s_fs_info = qs;

        sb_set_blocksize(s, QNX4_BLOCK_SIZE);

        s->s_op = &qnx4_sops;
        s->s_magic = QNX4_SUPER_MAGIC;
        s->s_flags |= SB_RDONLY;        /* Yup, read-only yet */
        s->s_time_min = 0;
        s->s_time_max = U32_MAX;

        /* Check the superblock signature. Since the qnx4 code is
           dangerous, we should leave as quickly as possible
           if we don't belong here... */
        bh = sb_bread(s, 1);
        if (!bh) {
                printk(KERN_ERR "qnx4: unable to read the superblock\n");
                return -EINVAL;
        }

        /* check before allocating dentries, inodes, .. */
        errmsg = qnx4_checkroot(s, (struct qnx4_super_block *) bh->b_data);
        brelse(bh);
        if (errmsg != NULL) {
                if (!silent)
                        printk(KERN_ERR "qnx4: %s\n", errmsg);
                return -EINVAL;
        }

        /* does root not have inode number QNX4_ROOT_INO ?? */
        root = qnx4_iget(s, QNX4_ROOT_INO * QNX4_INODES_PER_BLOCK);
        if (IS_ERR(root)) {
                printk(KERN_ERR "qnx4: get inode failed\n");
                return PTR_ERR(root);
        }

        s->s_root = d_make_root(root);
        if (s->s_root == NULL)
                return -ENOMEM;

        return 0;
}

static int qnx4_get_tree(struct fs_context *fc)
{
        return get_tree_bdev(fc, qnx4_fill_super);
}

static int qnx4_init_fs_context(struct fs_context *fc)
{
        fc->ops = &qnx4_context_opts;

        return 0;
}

static void qnx4_kill_sb(struct super_block *sb)
{
        struct qnx4_sb_info *qs = qnx4_sb(sb);
        kill_block_super(sb);
        if (qs) {
                kfree(qs->BitMap);
                kfree(qs);
        }
}

static int qnx4_read_folio(struct file *file, struct folio *folio)
{
        return block_read_full_folio(folio, qnx4_get_block);
}

static sector_t qnx4_bmap(struct address_space *mapping, sector_t block)
{
        return generic_block_bmap(mapping,block,qnx4_get_block);
}

static const struct address_space_operations qnx4_aops = {
        .read_folio     = qnx4_read_folio,
        .bmap           = qnx4_bmap
};

struct inode *qnx4_iget(struct super_block *sb, unsigned long ino)
{
        struct buffer_head *bh;
        struct qnx4_inode_entry *raw_inode;
        int block;
        struct qnx4_inode_entry *qnx4_inode;
        struct inode *inode;

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

        qnx4_inode = qnx4_raw_inode(inode);
        inode->i_mode = 0;

        QNX4DEBUG((KERN_INFO "reading inode : [%d]\n", ino));
        if (!ino) {
                printk(KERN_ERR "qnx4: bad inode number on dev %s: %lu is "
                                "out of range\n",
                       sb->s_id, ino);
                iget_failed(inode);
                return ERR_PTR(-EIO);
        }
        block = ino / QNX4_INODES_PER_BLOCK;

        if (!(bh = sb_bread(sb, block))) {
                printk(KERN_ERR "qnx4: major problem: unable to read inode from dev "
                       "%s\n", sb->s_id);
                iget_failed(inode);
                return ERR_PTR(-EIO);
        }
        raw_inode = ((struct qnx4_inode_entry *) bh->b_data) +
            (ino % QNX4_INODES_PER_BLOCK);

        inode->i_mode    = le16_to_cpu(raw_inode->di_mode);
        i_uid_write(inode, (uid_t)le16_to_cpu(raw_inode->di_uid));
        i_gid_write(inode, (gid_t)le16_to_cpu(raw_inode->di_gid));
        set_nlink(inode, le16_to_cpu(raw_inode->di_nlink));
        inode->i_size    = le32_to_cpu(raw_inode->di_size);
        inode_set_mtime(inode, le32_to_cpu(raw_inode->di_mtime), 0);
        inode_set_atime(inode, le32_to_cpu(raw_inode->di_atime), 0);
        inode_set_ctime(inode, le32_to_cpu(raw_inode->di_ctime), 0);
        inode->i_blocks  = le32_to_cpu(raw_inode->di_first_xtnt.xtnt_size);

        memcpy(qnx4_inode, raw_inode, QNX4_DIR_ENTRY_SIZE);
        if (S_ISREG(inode->i_mode)) {
                inode->i_fop = &generic_ro_fops;
                inode->i_mapping->a_ops = &qnx4_aops;
                qnx4_i(inode)->mmu_private = inode->i_size;
        } else if (S_ISDIR(inode->i_mode)) {
                inode->i_op = &qnx4_dir_inode_operations;
                inode->i_fop = &qnx4_dir_operations;
        } else if (S_ISLNK(inode->i_mode)) {
                inode->i_op = &page_symlink_inode_operations;
                inode_nohighmem(inode);
                inode->i_mapping->a_ops = &qnx4_aops;
                qnx4_i(inode)->mmu_private = inode->i_size;
        } else {
                printk(KERN_ERR "qnx4: bad inode %lu on dev %s\n",
                        ino, sb->s_id);
                iget_failed(inode);
                brelse(bh);
                return ERR_PTR(-EIO);
        }
        brelse(bh);
        unlock_new_inode(inode);
        return inode;
}

static struct kmem_cache *qnx4_inode_cachep;

static struct inode *qnx4_alloc_inode(struct super_block *sb)
{
        struct qnx4_inode_info *ei;
        ei = alloc_inode_sb(sb, qnx4_inode_cachep, GFP_KERNEL);
        if (!ei)
                return NULL;
        return &ei->vfs_inode;
}

static void qnx4_free_inode(struct inode *inode)
{
        kmem_cache_free(qnx4_inode_cachep, qnx4_i(inode));
}

static void init_once(void *foo)
{
        struct qnx4_inode_info *ei = (struct qnx4_inode_info *) foo;

        inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
        qnx4_inode_cachep = kmem_cache_create("qnx4_inode_cache",
                                             sizeof(struct qnx4_inode_info),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_ACCOUNT),
                                             init_once);
        if (qnx4_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(qnx4_inode_cachep);
}

static struct file_system_type qnx4_fs_type = {
        .owner                  = THIS_MODULE,
        .name                   = "qnx4",
        .kill_sb                = qnx4_kill_sb,
        .fs_flags               = FS_REQUIRES_DEV,
        .init_fs_context        = qnx4_init_fs_context,
};
MODULE_ALIAS_FS("qnx4");

static int __init init_qnx4_fs(void)
{
        int err;

        err = init_inodecache();
        if (err)
                return err;

        err = register_filesystem(&qnx4_fs_type);
        if (err) {
                destroy_inodecache();
                return err;
        }

        printk(KERN_INFO "QNX4 filesystem 0.2.3 registered.\n");
        return 0;
}

static void __exit exit_qnx4_fs(void)
{
        unregister_filesystem(&qnx4_fs_type);
        destroy_inodecache();
}

module_init(init_qnx4_fs)
module_exit(exit_qnx4_fs)
MODULE_DESCRIPTION("QNX4 file system");
MODULE_LICENSE("GPL");