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TOMOYO Linux Cross Reference
Linux/fs/bfs/file.c

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  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 
 24 const 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 
 34 static 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 
 50 static 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 
 65 static 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);
149 out:
150         mutex_unlock(&info->bfs_lock);
151         return err;
152 }
153 
154 static int bfs_writepage(struct page *page, struct writeback_control *wbc)
155 {
156         return block_write_full_page(page, bfs_get_block, wbc);
157 }
158 
159 static int bfs_readpage(struct file *file, struct page *page)
160 {
161         return block_read_full_page(page, bfs_get_block);
162 }
163 
164 static 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 
181 static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
182 {
183         return generic_block_bmap(mapping, block, bfs_get_block);
184 }
185 
186 const 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 
194 const struct inode_operations bfs_file_inops;
195 

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