xref: /openbmc/linux/fs/bfs/file.c (revision e9dde5a9)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *	fs/bfs/file.c
4  *	BFS file operations.
5  *	Copyright (C) 1999-2018 Tigran Aivazian <aivazian.tigran@gmail.com>
6  *
7  *	Make the file block allocation algorithm understand the size
8  *	of the underlying block device.
9  *	Copyright (C) 2007 Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
10  *
11  */
12 
13 #include <linux/fs.h>
14 #include <linux/buffer_head.h>
15 #include "bfs.h"
16 
17 #undef DEBUG
18 
19 #ifdef DEBUG
20 #define dprintf(x...)	printf(x)
21 #else
22 #define dprintf(x...)
23 #endif
24 
25 const struct file_operations bfs_file_operations = {
26 	.llseek 	= generic_file_llseek,
27 	.read_iter	= generic_file_read_iter,
28 	.write_iter	= generic_file_write_iter,
29 	.mmap		= generic_file_mmap,
30 	.splice_read	= filemap_splice_read,
31 };
32 
33 static int bfs_move_block(unsigned long from, unsigned long to,
34 					struct super_block *sb)
35 {
36 	struct buffer_head *bh, *new;
37 
38 	bh = sb_bread(sb, from);
39 	if (!bh)
40 		return -EIO;
41 	new = sb_getblk(sb, to);
42 	memcpy(new->b_data, bh->b_data, bh->b_size);
43 	mark_buffer_dirty(new);
44 	bforget(bh);
45 	brelse(new);
46 	return 0;
47 }
48 
49 static int bfs_move_blocks(struct super_block *sb, unsigned long start,
50 				unsigned long end, unsigned long where)
51 {
52 	unsigned long i;
53 
54 	dprintf("%08lx-%08lx->%08lx\n", start, end, where);
55 	for (i = start; i <= end; i++)
56 		if(bfs_move_block(i, where + i, sb)) {
57 			dprintf("failed to move block %08lx -> %08lx\n", i,
58 								where + i);
59 			return -EIO;
60 		}
61 	return 0;
62 }
63 
64 static int bfs_get_block(struct inode *inode, sector_t block,
65 			struct buffer_head *bh_result, int create)
66 {
67 	unsigned long phys;
68 	int err;
69 	struct super_block *sb = inode->i_sb;
70 	struct bfs_sb_info *info = BFS_SB(sb);
71 	struct bfs_inode_info *bi = BFS_I(inode);
72 
73 	phys = bi->i_sblock + block;
74 	if (!create) {
75 		if (phys <= bi->i_eblock) {
76 			dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
77                                 create, (unsigned long)block, phys);
78 			map_bh(bh_result, sb, phys);
79 		}
80 		return 0;
81 	}
82 
83 	/*
84 	 * If the file is not empty and the requested block is within the
85 	 * range of blocks allocated for this file, we can grant it.
86 	 */
87 	if (bi->i_sblock && (phys <= bi->i_eblock)) {
88 		dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n",
89 				create, (unsigned long)block, phys);
90 		map_bh(bh_result, sb, phys);
91 		return 0;
92 	}
93 
94 	/* The file will be extended, so let's see if there is enough space. */
95 	if (phys >= info->si_blocks)
96 		return -ENOSPC;
97 
98 	/* The rest has to be protected against itself. */
99 	mutex_lock(&info->bfs_lock);
100 
101 	/*
102 	 * If the last data block for this file is the last allocated
103 	 * block, we can extend the file trivially, without moving it
104 	 * anywhere.
105 	 */
106 	if (bi->i_eblock == info->si_lf_eblk) {
107 		dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n",
108 				create, (unsigned long)block, phys);
109 		map_bh(bh_result, sb, phys);
110 		info->si_freeb -= phys - bi->i_eblock;
111 		info->si_lf_eblk = bi->i_eblock = phys;
112 		mark_inode_dirty(inode);
113 		err = 0;
114 		goto out;
115 	}
116 
117 	/* Ok, we have to move this entire file to the next free block. */
118 	phys = info->si_lf_eblk + 1;
119 	if (phys + block >= info->si_blocks) {
120 		err = -ENOSPC;
121 		goto out;
122 	}
123 
124 	if (bi->i_sblock) {
125 		err = bfs_move_blocks(inode->i_sb, bi->i_sblock,
126 						bi->i_eblock, phys);
127 		if (err) {
128 			dprintf("failed to move ino=%08lx -> fs corruption\n",
129 								inode->i_ino);
130 			goto out;
131 		}
132 	} else
133 		err = 0;
134 
135 	dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
136                 create, (unsigned long)block, phys);
137 	bi->i_sblock = phys;
138 	phys += block;
139 	info->si_lf_eblk = bi->i_eblock = phys;
140 
141 	/*
142 	 * This assumes nothing can write the inode back while we are here
143 	 * and thus update inode->i_blocks! (XXX)
144 	 */
145 	info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
146 	mark_inode_dirty(inode);
147 	map_bh(bh_result, sb, phys);
148 out:
149 	mutex_unlock(&info->bfs_lock);
150 	return err;
151 }
152 
153 static int bfs_writepage(struct page *page, struct writeback_control *wbc)
154 {
155 	return block_write_full_page(page, bfs_get_block, wbc);
156 }
157 
158 static int bfs_read_folio(struct file *file, struct folio *folio)
159 {
160 	return block_read_full_folio(folio, bfs_get_block);
161 }
162 
163 static void bfs_write_failed(struct address_space *mapping, loff_t to)
164 {
165 	struct inode *inode = mapping->host;
166 
167 	if (to > inode->i_size)
168 		truncate_pagecache(inode, inode->i_size);
169 }
170 
171 static int bfs_write_begin(struct file *file, struct address_space *mapping,
172 			loff_t pos, unsigned len,
173 			struct page **pagep, void **fsdata)
174 {
175 	int ret;
176 
177 	ret = block_write_begin(mapping, pos, len, pagep, bfs_get_block);
178 	if (unlikely(ret))
179 		bfs_write_failed(mapping, pos + len);
180 
181 	return ret;
182 }
183 
184 static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
185 {
186 	return generic_block_bmap(mapping, block, bfs_get_block);
187 }
188 
189 const struct address_space_operations bfs_aops = {
190 	.dirty_folio	= block_dirty_folio,
191 	.invalidate_folio = block_invalidate_folio,
192 	.read_folio	= bfs_read_folio,
193 	.writepage	= bfs_writepage,
194 	.write_begin	= bfs_write_begin,
195 	.write_end	= generic_write_end,
196 	.bmap		= bfs_bmap,
197 };
198 
199 const struct inode_operations bfs_file_inops;
200