WSL2-Linux-Kernel/fs/bfs/file.c

/*
 *	fs/bfs/file.c
 *	BFS file operations.
 *	Copyright (C) 1999,2000 Tigran Aivazian <tigran@veritas.com>
 */

#include <linux/fs.h>
#include <linux/buffer_head.h>
#include <linux/smp_lock.h>
#include "bfs.h"

#undef DEBUG

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

const struct file_operations bfs_file_operations = {
	.llseek 	= generic_file_llseek,
	.read		= do_sync_read,
	.aio_read	= generic_file_aio_read,
	.write		= do_sync_write,
	.aio_write	= generic_file_aio_write,
	.mmap		= generic_file_mmap,
	.splice_read	= generic_file_splice_read,
};

static int bfs_move_block(unsigned long from, unsigned long to, struct super_block *sb)
{
	struct buffer_head *bh, *new;

	bh = sb_bread(sb, from);
	if (!bh)
		return -EIO;
	new = sb_getblk(sb, to);
	memcpy(new->b_data, bh->b_data, bh->b_size);
	mark_buffer_dirty(new);
	bforget(bh);
	brelse(new);
	return 0;
}

static int bfs_move_blocks(struct super_block *sb, unsigned long start,
                           unsigned long end, unsigned long where)
{
	unsigned long i;

	dprintf("%08lx-%08lx->%08lx\n", start, end, where);
	for (i = start; i <= end; i++)
		if(bfs_move_block(i, where + i, sb)) {
			dprintf("failed to move block %08lx -> %08lx\n", i, where + i);
			return -EIO;
		}
	return 0;
}

static int bfs_get_block(struct inode * inode, sector_t block, 
	struct buffer_head * bh_result, int create)
{
	unsigned long phys;
	int err;
	struct super_block *sb = inode->i_sb;
	struct bfs_sb_info *info = BFS_SB(sb);
	struct bfs_inode_info *bi = BFS_I(inode);
	struct buffer_head *sbh = info->si_sbh;

	if (block > info->si_blocks)
		return -EIO;

	phys = bi->i_sblock + block;
	if (!create) {
		if (phys <= bi->i_eblock) {
			dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
                                create, (unsigned long)block, phys);
			map_bh(bh_result, sb, phys);
		}
		return 0;
	}

	/* if the file is not empty and the requested block is within the range
	   of blocks allocated for this file, we can grant it */
	if (inode->i_size && phys <= bi->i_eblock) {
		dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
				create, (unsigned long)block, phys);
		map_bh(bh_result, sb, phys);
		return 0;
	}

	/* the rest has to be protected against itself */
	lock_kernel();

	/* if the last data block for this file is the last allocated
	   block, we can extend the file trivially, without moving it
	   anywhere */
	if (bi->i_eblock == info->si_lf_eblk) {
		dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
				create, (unsigned long)block, phys);
		map_bh(bh_result, sb, phys);
		info->si_freeb -= phys - bi->i_eblock;
		info->si_lf_eblk = bi->i_eblock = phys;
		mark_inode_dirty(inode);
		mark_buffer_dirty(sbh);
		err = 0;
		goto out;
	}

	/* Ok, we have to move this entire file to the next free block */
	phys = info->si_lf_eblk + 1;
	if (bi->i_sblock) { /* if data starts on block 0 then there is no data */
		err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
				bi->i_eblock, phys);
		if (err) {
			dprintf("failed to move ino=%08lx -> fs corruption\n", inode->i_ino);
			goto out;
		}
	} else
		err = 0;

	dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
                create, (unsigned long)block, phys);
	bi->i_sblock = phys;
	phys += block;
	info->si_lf_eblk = bi->i_eblock = phys;

	/* this assumes nothing can write the inode back while we are here
	 * and thus update inode->i_blocks! (XXX)*/
	info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
	mark_inode_dirty(inode);
	mark_buffer_dirty(sbh);
	map_bh(bh_result, sb, phys);
out:
	unlock_kernel();
	return err;
}

static int bfs_writepage(struct page *page, struct writeback_control *wbc)
{
	return block_write_full_page(page, bfs_get_block, wbc);
}

static int bfs_readpage(struct file *file, struct page *page)
{
	return block_read_full_page(page, bfs_get_block);
}

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

static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
{
	return generic_block_bmap(mapping, block, bfs_get_block);
}

const struct address_space_operations bfs_aops = {
	.readpage	= bfs_readpage,
	.writepage	= bfs_writepage,
	.sync_page	= block_sync_page,
	.prepare_write	= bfs_prepare_write,
	.commit_write	= generic_commit_write,
	.bmap		= bfs_bmap,
};

const struct inode_operations bfs_file_inops;