/*
 *  linux/fs/block_dev.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/mm.h>
#include <linux/locks.h>
#include <linux/fcntl.h>

#include <asm/uaccess.h>

extern int *blk_size[];
extern int *blksize_size[];

#define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
#define NBUF 64

ssize_t block_write(struct file * filp, const char * buf,
		    size_t count, loff_t *ppos)
{
	struct inode * inode = filp->f_dentry->d_inode;
	ssize_t blocksize, blocksize_bits, i, buffercount, write_error;
	ssize_t block, blocks;
	loff_t offset;
	ssize_t chars;
	ssize_t written = 0;
	struct buffer_head * bhlist[NBUF];
	size_t size;
	kdev_t dev;
	struct buffer_head * bh, *bufferlist[NBUF];
	register char * p;

	write_error = buffercount = 0;
	dev = inode->i_rdev;
	if ( is_read_only( inode->i_rdev ))
		return -EPERM;
	blocksize = BLOCK_SIZE;
	if (blksize_size[MAJOR(dev)] && blksize_size[MAJOR(dev)][MINOR(dev)])
		blocksize = blksize_size[MAJOR(dev)][MINOR(dev)];

	i = blocksize;
	blocksize_bits = 0;
	while(i != 1) {
		blocksize_bits++;
		i >>= 1;
	}

	block = *ppos >> blocksize_bits;
	offset = *ppos & (blocksize-1);

	if (blk_size[MAJOR(dev)])
		size = ((loff_t) blk_size[MAJOR(dev)][MINOR(dev)] << BLOCK_SIZE_BITS) >> blocksize_bits;
	else
		size = INT_MAX;
	while (count>0) {
		if (block >= size)
			return written ? written : -ENOSPC;
		chars = blocksize - offset;
		if (chars > count)
			chars=count;

#if 0
		/* get the buffer head */
		{
			struct buffer_head * (*fn)(kdev_t, int, int) = getblk;
			if (chars != blocksize)
				fn = bread;
			bh = fn(dev, block, blocksize);
		}
#else
		bh = getblk(dev, block, blocksize);

		if (chars != blocksize && !buffer_uptodate(bh)) {
		  if(!filp->f_reada ||
		     !read_ahead[MAJOR(dev)]) {
		    /* We do this to force the read of a single buffer */
		    brelse(bh);
		    bh = bread(dev,block,blocksize);
		  } else {
		    /* Read-ahead before write */
		    blocks = read_ahead[MAJOR(dev)] / (blocksize >> 9) / 2;
		    if (block + blocks > size) blocks = size - block;
		    if (blocks > NBUF) blocks=NBUF;
		    bhlist[0] = bh;
		    for(i=1; i<blocks; i++){
		      bhlist[i] = getblk (dev, block+i, blocksize);
		      if(!bhlist[i]){
			while(i >= 0) brelse(bhlist[i--]);
			return written ? written : -EIO;
		      };
		    };
		    ll_rw_block(READ, blocks, bhlist);
		    for(i=1; i<blocks; i++) brelse(bhlist[i]);
		    wait_on_buffer(bh);
		      
		  };
		};
#endif
		block++;
		if (!bh)
			return written ? written : -EIO;
		p = offset + bh->b_data;
		offset = 0;
		*ppos += chars;
		written += chars;
		count -= chars;
		copy_from_user(p,buf,chars);
		p += chars;
		buf += chars;
		mark_buffer_uptodate(bh, 1);
		mark_buffer_dirty(bh, 0);
		if (filp->f_flags & O_SYNC)
			bufferlist[buffercount++] = bh;
		else
			brelse(bh);
		if (buffercount == NBUF){
			ll_rw_block(WRITE, buffercount, bufferlist);
			for(i=0; i<buffercount; i++){
				wait_on_buffer(bufferlist[i]);
				if (!buffer_uptodate(bufferlist[i]))
					write_error=1;
				brelse(bufferlist[i]);
			}
			buffercount=0;
		}
		balance_dirty(dev);
		if (write_error)
			break;
	}
	if ( buffercount ){
		ll_rw_block(WRITE, buffercount, bufferlist);
		for(i=0; i<buffercount; i++){
			wait_on_buffer(bufferlist[i]);
			if (!buffer_uptodate(bufferlist[i]))
				write_error=1;
			brelse(bufferlist[i]);
		}
	}		
	filp->f_reada = 1;
	if(write_error)
		return -EIO;
	return written;
}

ssize_t block_read(struct file * filp, char * buf, size_t count, loff_t *ppos)
{
	struct inode * inode = filp->f_dentry->d_inode;
	size_t block;
	loff_t offset;
	ssize_t blocksize;
	ssize_t blocksize_bits, i;
	size_t blocks, rblocks, left;
	int bhrequest, uptodate;
	struct buffer_head ** bhb, ** bhe;
	struct buffer_head * buflist[NBUF];
	struct buffer_head * bhreq[NBUF];
	unsigned int chars;
	loff_t size;
	kdev_t dev;
	ssize_t read;

	dev = inode->i_rdev;
	blocksize = BLOCK_SIZE;
	if (blksize_size[MAJOR(dev)] && blksize_size[MAJOR(dev)][MINOR(dev)])
		blocksize = blksize_size[MAJOR(dev)][MINOR(dev)];
	i = blocksize;
	blocksize_bits = 0;
	while (i != 1) {
		blocksize_bits++;
		i >>= 1;
	}

	offset = *ppos;
	if (blk_size[MAJOR(dev)])
		size = (loff_t) blk_size[MAJOR(dev)][MINOR(dev)] << BLOCK_SIZE_BITS;
	else
		size = INT_MAX;

	if (offset > size)
		left = 0;
	/* size - offset might not fit into left, so check explicitly. */
	else if (size - offset > INT_MAX)
		left = INT_MAX;
	else
		left = size - offset;
	if (left > count)
		left = count;
	if (left <= 0)
		return 0;
	read = 0;
	block = offset >> blocksize_bits;
	offset &= blocksize-1;
	size >>= blocksize_bits;
	rblocks = blocks = (left + offset + blocksize - 1) >> blocksize_bits;
	bhb = bhe = buflist;
	if (filp->f_reada) {
	        if (blocks < read_ahead[MAJOR(dev)] / (blocksize >> 9))
			blocks = read_ahead[MAJOR(dev)] / (blocksize >> 9);
		if (rblocks > blocks)
			blocks = rblocks;
		
	}
	if (block + blocks > size) {
		blocks = size - block;
		if (blocks == 0)
			return 0;
	}

	/* We do this in a two stage process.  We first try to request
	   as many blocks as we can, then we wait for the first one to
	   complete, and then we try to wrap up as many as are actually
	   done.  This routine is rather generic, in that it can be used
	   in a filesystem by substituting the appropriate function in
	   for getblk.

	   This routine is optimized to make maximum use of the various
	   buffers and caches. */

	do {
		bhrequest = 0;
		uptodate = 1;
		while (blocks) {
			--blocks;
			*bhb = getblk(dev, block++, blocksize);
			if (*bhb && !buffer_uptodate(*bhb)) {
				uptodate = 0;
				bhreq[bhrequest++] = *bhb;
			}

			if (++bhb == &buflist[NBUF])
				bhb = buflist;

			/* If the block we have on hand is uptodate, go ahead
			   and complete processing. */
			if (uptodate)
				break;
			if (bhb == bhe)
				break;
		}

		/* Now request them all */
		if (bhrequest) {
			ll_rw_block(READ, bhrequest, bhreq);
		}

		do { /* Finish off all I/O that has actually completed */
			if (*bhe) {
				wait_on_buffer(*bhe);
				if (!buffer_uptodate(*bhe)) {	/* read error? */
				        brelse(*bhe);
					if (++bhe == &buflist[NBUF])
					  bhe = buflist;
					left = 0;
					break;
				}
			}			
			if (left < blocksize - offset)
				chars = left;
			else
				chars = blocksize - offset;
			*ppos += chars;
			left -= chars;
			read += chars;
			if (*bhe) {
				copy_to_user(buf,offset+(*bhe)->b_data,chars);
				brelse(*bhe);
				buf += chars;
			} else {
				while (chars-- > 0)
					put_user(0,buf++);
			}
			offset = 0;
			if (++bhe == &buflist[NBUF])
				bhe = buflist;
		} while (left > 0 && bhe != bhb && (!*bhe || !buffer_locked(*bhe)));
		if (bhe == bhb && !blocks)
			break;
	} while (left > 0);

/* Release the read-ahead blocks */
	while (bhe != bhb) {
		brelse(*bhe);
		if (++bhe == &buflist[NBUF])
			bhe = buflist;
	};
	if (!read)
		return -EIO;
	filp->f_reada = 1;
	return read;
}

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