/*
 *  linux/fs/block_dev.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
 */

#include <linux/config.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/locks.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/major.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/smp_lock.h>
#include <linux/iobuf.h>
#include <linux/highmem.h>
#include <linux/blkdev.h>
#include <linux/module.h>

#include <asm/uaccess.h>

static unsigned long max_block(kdev_t dev)
{
        unsigned int retval = ~0U;
        int major = MAJOR(dev);

        if (blk_size[major]) {
                int minor = MINOR(dev);
                unsigned int blocks = blk_size[major][minor];
                if (blocks) {
                        unsigned int size = block_size(dev);
                        unsigned int sizebits = blksize_bits(size);
                        blocks += (size-1) >> BLOCK_SIZE_BITS;
                        retval = blocks << (BLOCK_SIZE_BITS - sizebits);
                        if (sizebits > BLOCK_SIZE_BITS)
                                retval = blocks >> (sizebits - BLOCK_SIZE_BITS);
                }
        }
        return retval;
}

static loff_t blkdev_size(kdev_t dev)
{
        unsigned int blocks = ~0U;
        int major = MAJOR(dev);

        if (blk_size[major]) {
                int minor = MINOR(dev);
                blocks = blk_size[major][minor];
        }
        return (loff_t) blocks << BLOCK_SIZE_BITS;
}

/* Kill _all_ buffers, dirty or not.. */
static void kill_bdev(struct block_device *bdev)
{
        invalidate_bdev(bdev, 1);
        truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
}       

int set_blocksize(kdev_t dev, int size)
{
        int oldsize;
        struct block_device *bdev;

        /* Size must be a power of two, and between 512 and PAGE_SIZE */
        if (size > PAGE_SIZE || size < 512 || (size & (size-1)))
                return -EINVAL;

        /* Size cannot be smaller than the size supported by the device */
        if (size < get_hardsect_size(dev))
                return -EINVAL;

        /* No blocksize array? Implies hardcoded BLOCK_SIZE */
        if (!blksize_size[MAJOR(dev)]) {
                if (size == BLOCK_SIZE)
                        return 0;
                return -EINVAL;
        }

        oldsize = blksize_size[MAJOR(dev)][MINOR(dev)];
        if (oldsize == size)
                return 0;

        if (!oldsize && size == BLOCK_SIZE) {
                blksize_size[MAJOR(dev)][MINOR(dev)] = size;
                return 0;
        }

        /* Ok, we're actually changing the blocksize.. */
        bdev = bdget(dev);
        sync_buffers(dev, 2);
        blksize_size[MAJOR(dev)][MINOR(dev)] = size;
        bdev->bd_inode->i_blkbits = blksize_bits(size);
        kill_bdev(bdev);
        bdput(bdev);
        return 0;
}

int sb_set_blocksize(struct super_block *sb, int size)
{
        int bits;
        if (set_blocksize(sb->s_dev, size) < 0)
                return 0;
        sb->s_blocksize = size;
        for (bits = 9, size >>= 9; size >>= 1; bits++)
                ;
        sb->s_blocksize_bits = bits;
        return sb->s_blocksize;
}

int sb_min_blocksize(struct super_block *sb, int size)
{
        int minsize = get_hardsect_size(sb->s_dev);
        if (size < minsize)
                size = minsize;
        return sb_set_blocksize(sb, size);
}

static int blkdev_get_block(struct inode * inode, long iblock, struct buffer_head * bh, int create)
{
        if (iblock >= max_block(inode->i_rdev))
                return -EIO;

        bh->b_dev = inode->i_rdev;
        bh->b_blocknr = iblock;
        bh->b_state |= 1UL << BH_Mapped;
        return 0;
}

static int blkdev_direct_IO(int rw, struct inode * inode, struct kiobuf * iobuf, unsigned long blocknr, int blocksize)
{
        return generic_direct_IO(rw, inode, iobuf, blocknr, blocksize, blkdev_get_block);
}

static int blkdev_writepage(struct page * page)
{
        return block_write_full_page(page, blkdev_get_block);
}

static int blkdev_readpage(struct file * file, struct page * page)
{
        return block_read_full_page(page, blkdev_get_block);
}

static int blkdev_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
{
        return block_prepare_write(page, from, to, blkdev_get_block);
}

static int blkdev_commit_write(struct file *file, struct page *page, unsigned from, unsigned to)
{
        return block_commit_write(page, from, to);
}

/*
 * private llseek:
 * for a block special file file->f_dentry->d_inode->i_size is zero
 * so we compute the size by hand (just as in block_read/write above)
 */
static loff_t block_llseek(struct file *file, loff_t offset, int origin)
{
        /* ewww */
        loff_t size = file->f_dentry->d_inode->i_bdev->bd_inode->i_size;
        loff_t retval;

        switch (origin) {
                case 2:
                        offset += size;
                        break;
                case 1:
                        offset += file->f_pos;
        }
        retval = -EINVAL;
        if (offset >= 0 && offset <= size) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_reada = 0;
                        file->f_version = ++event;
                }
                retval = offset;
        }
        return retval;
}
        

static int __block_fsync(struct inode * inode)
{
        int ret, err;

        ret = filemap_fdatasync(inode->i_mapping);
        err = sync_buffers(inode->i_rdev, 1);
        if (err && !ret)
                ret = err;
        err = filemap_fdatawait(inode->i_mapping);
        if (err && !ret)
                ret = err;

        return ret;
}

/*
 *      Filp may be NULL when we are called by an msync of a vma
 *      since the vma has no handle.
 */
 
static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
{
        struct inode * inode = dentry->d_inode;

        return __block_fsync(inode);
}

/*
 * pseudo-fs
 */

static struct super_block *bd_read_super(struct super_block *sb, void *data, int silent)
{
        static struct super_operations sops = {};
        struct inode *root = new_inode(sb);
        if (!root)
                return NULL;
        root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR;
        root->i_uid = root->i_gid = 0;
        root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME;
        sb->s_maxbytes = ~0ULL;
        sb->s_blocksize = 1024;
        sb->s_blocksize_bits = 10;
        sb->s_magic = 0x62646576;
        sb->s_op = &sops;
        sb->s_root = d_alloc(NULL, &(const struct qstr) { "bdev:", 5, 0 });
        if (!sb->s_root) {
                iput(root);
                return NULL;
        }
        sb->s_root->d_sb = sb;
        sb->s_root->d_parent = sb->s_root;
        d_instantiate(sb->s_root, root);
        return sb;
}

static DECLARE_FSTYPE(bd_type, "bdev", bd_read_super, FS_NOMOUNT);

static struct vfsmount *bd_mnt;

/*
 * bdev cache handling - shamelessly stolen from inode.c
 * We use smaller hashtable, though.
 */

#define HASH_BITS       6
#define HASH_SIZE       (1UL << HASH_BITS)
#define HASH_MASK       (HASH_SIZE-1)
static struct list_head bdev_hashtable[HASH_SIZE];
static spinlock_t bdev_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
static kmem_cache_t * bdev_cachep;

#define alloc_bdev() \
         ((struct block_device *) kmem_cache_alloc(bdev_cachep, SLAB_KERNEL))
#define destroy_bdev(bdev) kmem_cache_free(bdev_cachep, (bdev))

static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
{
        struct block_device * bdev = (struct block_device *) foo;

        if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
            SLAB_CTOR_CONSTRUCTOR)
        {
                memset(bdev, 0, sizeof(*bdev));
                sema_init(&bdev->bd_sem, 1);
                INIT_LIST_HEAD(&bdev->bd_inodes);
        }
}

void __init bdev_cache_init(void)
{
        int i, err;
        struct list_head *head = bdev_hashtable;

        i = HASH_SIZE;
        do {
                INIT_LIST_HEAD(head);
                head++;
                i--;
        } while (i);

        bdev_cachep = kmem_cache_create("bdev_cache",
                                         sizeof(struct block_device),
                                         0, SLAB_HWCACHE_ALIGN, init_once,
                                         NULL);
        if (!bdev_cachep)
                panic("Cannot create bdev_cache SLAB cache");
        err = register_filesystem(&bd_type);
        if (err)
                panic("Cannot register bdev pseudo-fs");
        bd_mnt = kern_mount(&bd_type);
        err = PTR_ERR(bd_mnt);
        if (IS_ERR(bd_mnt))
                panic("Cannot create bdev pseudo-fs");
}

/*
 * Most likely _very_ bad one - but then it's hardly critical for small
 * /dev and can be fixed when somebody will need really large one.
 */
static inline unsigned long hash(dev_t dev)
{
        unsigned long tmp = dev;
        tmp = tmp + (tmp >> HASH_BITS) + (tmp >> HASH_BITS*2);
        return tmp & HASH_MASK;
}

static struct block_device *bdfind(dev_t dev, struct list_head *head)
{
        struct list_head *p;
        struct block_device *bdev;
        for (p=head->next; p!=head; p=p->next) {
                bdev = list_entry(p, struct block_device, bd_hash);
                if (bdev->bd_dev != dev)
                        continue;
                atomic_inc(&bdev->bd_count);
                return bdev;
        }
        return NULL;
}

struct block_device *bdget(dev_t dev)
{
        struct list_head * head = bdev_hashtable + hash(dev);
        struct block_device *bdev, *new_bdev;
        spin_lock(&bdev_lock);
        bdev = bdfind(dev, head);
        spin_unlock(&bdev_lock);
        if (bdev)
                return bdev;
        new_bdev = alloc_bdev();
        if (new_bdev) {
                struct inode *inode = new_inode(bd_mnt->mnt_sb);
                if (inode) {
                        kdev_t kdev = to_kdev_t(dev);
                        atomic_set(&new_bdev->bd_count,1);
                        new_bdev->bd_dev = dev;
                        new_bdev->bd_op = NULL;
                        new_bdev->bd_inode = inode;
                        inode->i_rdev = kdev;
                        inode->i_dev = kdev;
                        inode->i_bdev = new_bdev;
                        inode->i_data.a_ops = &def_blk_aops;
                        inode->i_data.gfp_mask = GFP_USER;
                        inode->i_mode = S_IFBLK;
                        spin_lock(&bdev_lock);
                        bdev = bdfind(dev, head);
                        if (!bdev) {
                                list_add(&new_bdev->bd_hash, head);
                                spin_unlock(&bdev_lock);
                                return new_bdev;
                        }
                        spin_unlock(&bdev_lock);
                        iput(new_bdev->bd_inode);
                }
                destroy_bdev(new_bdev);
        }
        return bdev;
}

static inline void __bd_forget(struct inode *inode)
{
        list_del_init(&inode->i_devices);
        inode->i_bdev = NULL;
        inode->i_mapping = &inode->i_data;
}

void bdput(struct block_device *bdev)
{
        if (atomic_dec_and_lock(&bdev->bd_count, &bdev_lock)) {
                struct list_head *p;
                if (bdev->bd_openers)
                        BUG();
                list_del(&bdev->bd_hash);
                while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
                        __bd_forget(list_entry(p, struct inode, i_devices));
                }
                spin_unlock(&bdev_lock);
                iput(bdev->bd_inode);
                destroy_bdev(bdev);
        }
}
 
int bd_acquire(struct inode *inode)
{
        struct block_device *bdev;
        spin_lock(&bdev_lock);
        if (inode->i_bdev) {
                atomic_inc(&inode->i_bdev->bd_count);
                spin_unlock(&bdev_lock);
                return 0;
        }
        spin_unlock(&bdev_lock);
        bdev = bdget(kdev_t_to_nr(inode->i_rdev));
        if (!bdev)
                return -ENOMEM;
        spin_lock(&bdev_lock);
        if (!inode->i_bdev) {
                inode->i_bdev = bdev;
                inode->i_mapping = bdev->bd_inode->i_mapping;
                list_add(&inode->i_devices, &bdev->bd_inodes);
        } else if (inode->i_bdev != bdev)
                BUG();
        spin_unlock(&bdev_lock);
        return 0;
}

/* Call when you free inode */

void bd_forget(struct inode *inode)
{
        spin_lock(&bdev_lock);
        if (inode->i_bdev)
                __bd_forget(inode);
        spin_unlock(&bdev_lock);
}

static struct {
        const char *name;
        struct block_device_operations *bdops;
} blkdevs[MAX_BLKDEV];

int get_blkdev_list(char * p)
{
        int i;
        int len;

        len = sprintf(p, "\nBlock devices:\n");
        for (i = 0; i < MAX_BLKDEV ; i++) {
                if (blkdevs[i].bdops) {
                        len += sprintf(p+len, "%3d %s\n", i, blkdevs[i].name);
                }
        }
        return len;
}

/*
        Return the function table of a device.
        Load the driver if needed.
*/
const struct block_device_operations * get_blkfops(unsigned int major)
{
        const struct block_device_operations *ret = NULL;

        /* major 0 is used for non-device mounts */
        if (major && major < MAX_BLKDEV) {
#ifdef CONFIG_KMOD
                if (!blkdevs[major].bdops) {
                        char name[20];
                        sprintf(name, "block-major-%d", major);
                        request_module(name);
                }
#endif
                ret = blkdevs[major].bdops;
        }
        return ret;
}

int register_blkdev(unsigned int major, const char * name, struct block_device_operations *bdops)
{
        if (major == 0) {
                for (major = MAX_BLKDEV-1; major > 0; major--) {
                        if (blkdevs[major].bdops == NULL) {
                                blkdevs[major].name = name;
                                blkdevs[major].bdops = bdops;
                                return major;
                        }
                }
                return -EBUSY;
        }
        if (major >= MAX_BLKDEV)
                return -EINVAL;
        if (blkdevs[major].bdops && blkdevs[major].bdops != bdops)
                return -EBUSY;
        blkdevs[major].name = name;
        blkdevs[major].bdops = bdops;
        return 0;
}

int unregister_blkdev(unsigned int major, const char * name)
{
        if (major >= MAX_BLKDEV)
                return -EINVAL;
        if (!blkdevs[major].bdops)
                return -EINVAL;
        if (strcmp(blkdevs[major].name, name))
                return -EINVAL;
        blkdevs[major].name = NULL;
        blkdevs[major].bdops = NULL;
        return 0;
}

/*
 * This routine checks whether a removable media has been changed,
 * and invalidates all buffer-cache-entries in that case. This
 * is a relatively slow routine, so we have to try to minimize using
 * it. Thus it is called only upon a 'mount' or 'open'. This
 * is the best way of combining speed and utility, I think.
 * People changing diskettes in the middle of an operation deserve
 * to lose :-)
 */
int check_disk_change(kdev_t dev)
{
        int i;
        const struct block_device_operations * bdops = NULL;

        i = MAJOR(dev);
        if (i < MAX_BLKDEV)
                bdops = blkdevs[i].bdops;
        if (bdops == NULL) {
                devfs_handle_t de;

                de = devfs_find_handle (NULL, NULL, i, MINOR (dev),
                                        DEVFS_SPECIAL_BLK, 0);
                if (de) {
                        bdops = devfs_get_ops (de);
                        devfs_put_ops (de); /* We're running in owner module */
                }
        }
        if (bdops == NULL)
                return 0;
        if (bdops->check_media_change == NULL)
                return 0;
        if (!bdops->check_media_change(dev))
                return 0;

        if (invalidate_device(dev, 0))
                printk("VFS: busy inodes on changed media.\n");

        if (bdops->revalidate)
                bdops->revalidate(dev);
        return 1;
}

int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
{
        int res;
        mm_segment_t old_fs = get_fs();

        if (!bdev->bd_op->ioctl)
                return -EINVAL;
        set_fs(KERNEL_DS);
        res = bdev->bd_op->ioctl(bdev->bd_inode, NULL, cmd, arg);
        set_fs(old_fs);
        return res;
}

static int do_open(struct block_device *bdev, struct inode *inode, struct file *file)
{
        int ret = -ENXIO;
        kdev_t dev = to_kdev_t(bdev->bd_dev);

        down(&bdev->bd_sem);
        lock_kernel();
        if (!bdev->bd_op)
                bdev->bd_op = get_blkfops(MAJOR(dev));
        if (bdev->bd_op) {
                ret = 0;
                if (bdev->bd_op->owner)
                        __MOD_INC_USE_COUNT(bdev->bd_op->owner);
                if (bdev->bd_op->open)
                        ret = bdev->bd_op->open(inode, file);
                if (!ret) {
                        bdev->bd_openers++;
                        bdev->bd_inode->i_size = blkdev_size(dev);
                        bdev->bd_inode->i_blkbits = blksize_bits(block_size(dev));
                } else {
                        if (bdev->bd_op->owner)
                                __MOD_DEC_USE_COUNT(bdev->bd_op->owner);
                        if (!bdev->bd_openers)
                                bdev->bd_op = NULL;
                }
        }
        unlock_kernel();
        up(&bdev->bd_sem);
        if (ret)
                bdput(bdev);
        return ret;
}

int blkdev_get(struct block_device *bdev, mode_t mode, unsigned flags, int kind)
{
        /*
         * This crockload is due to bad choice of ->open() type.
         * It will go away.
         * For now, block device ->open() routine must _not_
         * examine anything in 'inode' argument except ->i_rdev.
         */
        struct file fake_file = {};
        struct dentry fake_dentry = {};
        fake_file.f_mode = mode;
        fake_file.f_flags = flags;
        fake_file.f_dentry = &fake_dentry;
        fake_dentry.d_inode = bdev->bd_inode;

        return do_open(bdev, bdev->bd_inode, &fake_file);
}

int blkdev_open(struct inode * inode, struct file * filp)
{
        struct block_device *bdev;

        /*
         * Preserve backwards compatibility and allow large file access
         * even if userspace doesn't ask for it explicitly. Some mkfs
         * binary needs it. We might want to drop this workaround
         * during an unstable branch.
         */
        filp->f_flags |= O_LARGEFILE;

        bd_acquire(inode);
        bdev = inode->i_bdev;

        return do_open(bdev, inode, filp);
}       

int blkdev_put(struct block_device *bdev, int kind)
{
        int ret = 0;
        kdev_t rdev = to_kdev_t(bdev->bd_dev); /* this should become bdev */
        struct inode *bd_inode = bdev->bd_inode;

        down(&bdev->bd_sem);
        lock_kernel();
        if (kind == BDEV_FILE)
                __block_fsync(bd_inode);
        else if (kind == BDEV_FS)
                fsync_no_super(rdev);
        if (!--bdev->bd_openers)
                kill_bdev(bdev);
        if (bdev->bd_op->release)
                ret = bdev->bd_op->release(bd_inode, NULL);
        if (bdev->bd_op->owner)
                __MOD_DEC_USE_COUNT(bdev->bd_op->owner);
        if (!bdev->bd_openers)
                bdev->bd_op = NULL;
        unlock_kernel();
        up(&bdev->bd_sem);
        bdput(bdev);
        return ret;
}

int blkdev_close(struct inode * inode, struct file * filp)
{
        return blkdev_put(inode->i_bdev, BDEV_FILE);
}

static int blkdev_ioctl(struct inode *inode, struct file *file, unsigned cmd,
                        unsigned long arg)
{
        if (inode->i_bdev->bd_op->ioctl)
                return inode->i_bdev->bd_op->ioctl(inode, file, cmd, arg);
        return -EINVAL;
}

struct address_space_operations def_blk_aops = {
        readpage: blkdev_readpage,
        writepage: blkdev_writepage,
        sync_page: block_sync_page,
        prepare_write: blkdev_prepare_write,
        commit_write: blkdev_commit_write,
        direct_IO: blkdev_direct_IO,
};

struct file_operations def_blk_fops = {
        open:           blkdev_open,
        release:        blkdev_close,
        llseek:         block_llseek,
        read:           generic_file_read,
        write:          generic_file_write,
        mmap:           generic_file_mmap,
        fsync:          block_fsync,
        ioctl:          blkdev_ioctl,
};

const char * bdevname(kdev_t dev)
{
        static char buffer[32];
        const char * name = blkdevs[MAJOR(dev)].name;

        if (!name)
                name = "unknown-block";

        sprintf(buffer, "%s(%d,%d)", name, MAJOR(dev), MINOR(dev));
        return buffer;
}