1/*
  2 *	fs/bfs/file.c
  3 *	BFS file operations.
  4 *	Copyright (C) 1999,2000 Tigran Aivazian <tigran@veritas.com>
  5 *
  6 *	Make the file block allocation algorithm understand the size
  7 *	of the underlying block device.
  8 *	Copyright (C) 2007 Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
  9 *
 10 */
 11
 12#include <linux/fs.h>
 13#include <linux/buffer_head.h>
 14#include "bfs.h"
 15
 16#undef DEBUG
 17
 18#ifdef DEBUG
 19#define dprintf(x...)	printf(x)
 20#else
 21#define dprintf(x...)
 22#endif
 23
 24const struct file_operations bfs_file_operations = {
 25	.llseek 	= generic_file_llseek,
 26	.read		= do_sync_read,
 27	.aio_read	= generic_file_aio_read,
 28	.write		= do_sync_write,
 29	.aio_write	= generic_file_aio_write,
 30	.mmap		= generic_file_mmap,
 31	.splice_read	= generic_file_splice_read,
 32};
 33
 34static int bfs_move_block(unsigned long from, unsigned long to,
 35					struct super_block *sb)
 36{
 37	struct buffer_head *bh, *new;
 38
 39	bh = sb_bread(sb, from);
 40	if (!bh)
 41		return -EIO;
 42	new = sb_getblk(sb, to);
 43	memcpy(new->b_data, bh->b_data, bh->b_size);
 44	mark_buffer_dirty(new);
 45	bforget(bh);
 46	brelse(new);
 47	return 0;
 48}
 49
 50static int bfs_move_blocks(struct super_block *sb, unsigned long start,
 51				unsigned long end, unsigned long where)
 52{
 53	unsigned long i;
 54
 55	dprintf("%08lx-%08lx->%08lx\n", start, end, where);
 56	for (i = start; i <= end; i++)
 57		if(bfs_move_block(i, where + i, sb)) {
 58			dprintf("failed to move block %08lx -> %08lx\n", i,
 59								where + i);
 60			return -EIO;
 61		}
 62	return 0;
 63}
 64
 65static int bfs_get_block(struct inode *inode, sector_t block,
 66			struct buffer_head *bh_result, int create)
 67{
 68	unsigned long phys;
 69	int err;
 70	struct super_block *sb = inode->i_sb;
 71	struct bfs_sb_info *info = BFS_SB(sb);
 72	struct bfs_inode_info *bi = BFS_I(inode);
 73
 74	phys = bi->i_sblock + block;
 75	if (!create) {
 76		if (phys <= bi->i_eblock) {
 77			dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
 78                                create, (unsigned long)block, phys);
 79			map_bh(bh_result, sb, phys);
 80		}
 81		return 0;
 82	}
 83
 84	/*
 85	 * If the file is not empty and the requested block is within the
 86	 * range of blocks allocated for this file, we can grant it.
 87	 */
 88	if (bi->i_sblock && (phys <= bi->i_eblock)) {
 89		dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
 90				create, (unsigned long)block, phys);
 91		map_bh(bh_result, sb, phys);
 92		return 0;
 93	}
 94
 95	/* The file will be extended, so let's see if there is enough space. */
 96	if (phys >= info->si_blocks)
 97		return -ENOSPC;
 98
 99	/* The rest has to be protected against itself. */
100	mutex_lock(&info->bfs_lock);
101
102	/*
103	 * If the last data block for this file is the last allocated
104	 * block, we can extend the file trivially, without moving it
105	 * anywhere.
106	 */
107	if (bi->i_eblock == info->si_lf_eblk) {
108		dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
109				create, (unsigned long)block, phys);
110		map_bh(bh_result, sb, phys);
111		info->si_freeb -= phys - bi->i_eblock;
112		info->si_lf_eblk = bi->i_eblock = phys;
113		mark_inode_dirty(inode);
114		err = 0;
115		goto out;
116	}
117
118	/* Ok, we have to move this entire file to the next free block. */
119	phys = info->si_lf_eblk + 1;
120	if (phys + block >= info->si_blocks) {
121		err = -ENOSPC;
122		goto out;
123	}
124
125	if (bi->i_sblock) {
126		err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
127						bi->i_eblock, phys);
128		if (err) {
129			dprintf("failed to move ino=%08lx -> fs corruption\n",
130								inode->i_ino);
131			goto out;
132		}
133	} else
134		err = 0;
135
136	dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
137                create, (unsigned long)block, phys);
138	bi->i_sblock = phys;
139	phys += block;
140	info->si_lf_eblk = bi->i_eblock = phys;
141
142	/*
143	 * This assumes nothing can write the inode back while we are here
144	 * and thus update inode->i_blocks! (XXX)
145	 */
146	info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
147	mark_inode_dirty(inode);
148	map_bh(bh_result, sb, phys);
149out:
150	mutex_unlock(&info->bfs_lock);
151	return err;
152}
153
154static int bfs_writepage(struct page *page, struct writeback_control *wbc)
155{
156	return block_write_full_page(page, bfs_get_block, wbc);
157}
158
159static int bfs_readpage(struct file *file, struct page *page)
160{
161	return block_read_full_page(page, bfs_get_block);
162}
163
164static int bfs_write_begin(struct file *file, struct address_space *mapping,
165			loff_t pos, unsigned len, unsigned flags,
166			struct page **pagep, void **fsdata)
167{
168	int ret;
169
170	ret = block_write_begin(mapping, pos, len, flags, pagep,
171				bfs_get_block);
172	if (unlikely(ret)) {
173		loff_t isize = mapping->host->i_size;
174		if (pos + len > isize)
175			vmtruncate(mapping->host, isize);
176	}
177
178	return ret;
179}
180
181static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
182{
183	return generic_block_bmap(mapping, block, bfs_get_block);
184}
185
186const struct address_space_operations bfs_aops = {
187	.readpage	= bfs_readpage,
188	.writepage	= bfs_writepage,
189	.write_begin	= bfs_write_begin,
190	.write_end	= generic_write_end,
191	.bmap		= bfs_bmap,
192};
193
194const struct inode_operations bfs_file_inops;