1 /* This file is derived from source code for the Nachos
2 instructional operating system. The Nachos copyright notice
3 is reproduced in full below. */
5 /* Copyright (c) 1992-1996 The Regents of the University of California.
8 Permission to use, copy, modify, and distribute this software
9 and its documentation for any purpose, without fee, and
10 without written agreement is hereby granted, provided that the
11 above copyright notice and the following two paragraphs appear
12 in all copies of this software.
14 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO
15 ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
16 CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE
17 AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA
18 HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
20 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
21 WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
22 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
23 PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
24 BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
25 PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
29 #include "filesys/filesys.h"
34 #include "filesys/file.h"
35 #include "filesys/inode.h"
36 #include "filesys/directory.h"
37 #include "devices/disk.h"
41 For the purposes of the "user processes" assignment (project
42 2), please treat all the code in the filesys directory as a
43 black box. No changes should be needed. For that project, a
44 single lock external to the filesystem code suffices.
46 The filesystem consists of a set of files. Each file has a
47 header called an `index node' or `inode', represented by
48 struct inode, that is stored by itself in a single sector (see
49 inode.h). The header contains the file's length in bytes and
50 an array that lists the sector numbers for the file's
53 Two files are special. The first special file is the free
54 map, whose inode is always stored in sector 0
55 (FREE_MAP_SECTOR). The free map stores a bitmap (see
56 lib/bitmap.h) that contains one bit for each sector on the
57 disk. Each bit that corresponds to a sector within a file is
58 set to true, and the other bits, which are not part of any
59 file, are set to false.
61 The second special file is the root directory, whose inode is
62 always stored in sector 1 (ROOT_DIR_SECTOR). The root
63 directory file stores an array of `struct dir_entry' (see
64 directory.h), each of which, if it is in use, associates a
65 filename with the sector of the file's inode.
67 The filesystem implemented here has the following limitations:
69 - No synchronization. Concurrent accesses will interfere
70 with one another, so external synchronization is needed.
72 - File size is fixed at creation time. Because the root
73 directory is represented as a file, the number of files
74 that may be created is also limited.
76 - No indirect blocks. This limits maximum file size to the
77 number of sector pointers that fit in a single inode
78 times the size of a sector, or 126 * 512 == 63 kB given
79 32-bit sizes and 512-byte sectors.
83 - Filenames limited to 14 characters.
85 - A system crash mid-operation may corrupt the disk in a way
86 that cannot be repaired automatically. No `fsck' tool is
89 However one important feature is included:
91 - Unix-like semantics for filesys_remove() are implemented.
92 That is, if a file is open when it is removed, its blocks
93 are not deallocated and it may still be accessed by the
94 threads that have it open until the last one closes it. */
96 /* Sectors of system file inodes. */
97 #define FREE_MAP_SECTOR 0 /* Free map file inode sector. */
98 #define ROOT_DIR_SECTOR 1 /* Root directory file inode sector. */
100 /* Root directory. */
101 #define NUM_DIR_ENTRIES 10 /* Maximum number of directory entries. */
103 /* The disk that contains the filesystem. */
104 struct disk *filesys_disk;
106 /* The free map and root directory files.
107 These files are opened by filesys_init() and never closed. */
108 struct file *free_map_file, *root_dir_file;
110 static void do_format (void);
112 /* Initializes the filesystem module.
113 If FORMAT is true, reformats the filesystem. */
115 filesys_init (bool format)
119 filesys_disk = disk_get (0, 1);
120 if (filesys_disk == NULL)
121 PANIC ("hd0:1 (hdb) not present, filesystem initialization failed");
126 free_map_file = file_open (FREE_MAP_SECTOR);
127 if (free_map_file == NULL)
128 PANIC ("can't open free map file");
129 root_dir_file = file_open (ROOT_DIR_SECTOR);
130 if (root_dir_file == NULL)
131 PANIC ("can't open root dir file");
134 /* Shuts down the filesystem module, writing any unwritten data
136 Currently there's nothing to do. You'll need to add code here
137 when you implement write-behind caching. */
143 /* Creates a file named NAME with the given INITIAL_SIZE.
144 Returns true if successful, false otherwise.
145 Fails if a file named NAME already exists,
146 or if internal memory allocation fails. */
148 filesys_create (const char *name, off_t initial_size)
150 struct dir *dir = NULL;
151 struct bitmap *free_map = NULL;
152 struct inode *inode = NULL;
153 disk_sector_t inode_sector;
154 bool success = false;
156 /* Read the root directory. */
157 dir = dir_create (NUM_DIR_ENTRIES);
160 dir_read (dir, root_dir_file);
161 if (dir_lookup (dir, name, NULL))
164 /* Allocate a block for the inode. */
165 free_map = bitmap_create (disk_size (filesys_disk));
166 if (free_map == NULL)
168 bitmap_read (free_map, free_map_file);
169 inode_sector = bitmap_scan_and_flip (free_map, 0, 1, false);
170 if (inode_sector == BITMAP_ERROR)
173 /* Add the file to the directory. */
174 if (!dir_add (dir, name, inode_sector))
177 /* Allocate space for the file. */
178 inode = inode_create (free_map, inode_sector, initial_size);
182 /* Write everything back. */
183 inode_commit (inode);
184 dir_write (dir, root_dir_file);
185 bitmap_write (free_map, free_map_file);
192 bitmap_destroy (free_map);
198 /* Opens a file named NAME and initializes FILE for usage with
199 the file_*() functions declared in file.h.
200 Returns the new file if successful or a null pointer
202 Fails if no file named NAME exists,
203 or if an internal memory allocation fails. */
205 filesys_open (const char *name)
207 struct dir *dir = NULL;
208 struct file *file = NULL;
209 disk_sector_t inode_sector;
211 dir = dir_create (NUM_DIR_ENTRIES);
215 dir_read (dir, root_dir_file);
216 if (dir_lookup (dir, name, &inode_sector))
217 file = file_open (inode_sector);
225 /* Deletes the file named NAME.
226 Returns true if successful, false on failure.
227 Fails if no file named NAME exists,
228 or if an internal memory allocation fails. */
230 filesys_remove (const char *name)
232 struct dir *dir = NULL;
234 disk_sector_t inode_sector;
235 bool success = false;
237 /* Read the root directory. */
238 dir = dir_create (NUM_DIR_ENTRIES);
241 dir_read (dir, root_dir_file);
242 if (!dir_lookup (dir, name, &inode_sector))
245 /* Open the inode and delete it it. */
246 inode = inode_open (inode_sector);
249 inode_remove (inode);
252 /* Remove file from root directory and write directory back to
254 dir_remove (dir, name);
255 dir_write (dir, root_dir_file);
266 /* Prints a list of files in the filesystem to the system
268 Returns true if successful, false on failure,
269 which occurs only if an internal memory allocation fails. */
273 struct dir *dir = dir_create (NUM_DIR_ENTRIES);
276 dir_read (dir, root_dir_file);
283 /* Dumps the filesystem state to the system console,
284 including the free map, the list of files, and file contents.
285 Returns true if successful, false on failure,
286 which occurs only if an internal memory allocation fails. */
290 struct bitmap *free_map;
293 printf ("Free map:\n");
294 free_map = bitmap_create (disk_size (filesys_disk));
295 if (free_map == NULL)
297 bitmap_read (free_map, free_map_file);
298 bitmap_dump (free_map);
299 bitmap_destroy (free_map);
302 dir = dir_create (NUM_DIR_ENTRIES);
305 dir_read (dir, root_dir_file);
312 static void must_succeed_function (int, bool) NO_INLINE;
313 #define MUST_SUCCEED(EXPR) must_succeed_function (__LINE__, EXPR)
315 /* Performs basic sanity checks on the filesystem.
316 The filesystem should not contain a file named `foo' when
319 filesys_self_test (void)
321 static const char s[] = "This is a test string.";
322 static const char zeros[sizeof s] = {0};
327 filesys_remove ("foo");
328 for (i = 0; i < 2; i++)
330 /* Create file and check that it contains zeros
331 throughout the created length. */
332 MUST_SUCCEED (filesys_create ("foo", sizeof s));
333 MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
334 MUST_SUCCEED (file_read (file, s2, sizeof s2) == sizeof s2);
335 MUST_SUCCEED (memcmp (s2, zeros, sizeof s) == 0);
336 MUST_SUCCEED (file_tell (file) == sizeof s);
337 MUST_SUCCEED (file_length (file) == sizeof s);
340 /* Reopen file and write to it. */
341 MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
342 MUST_SUCCEED (file_write (file, s, sizeof s) == sizeof s);
343 MUST_SUCCEED (file_tell (file) == sizeof s);
344 MUST_SUCCEED (file_length (file) == sizeof s);
347 /* Reopen file and verify that it reads back correctly.
348 Delete file while open to check proper semantics. */
349 MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
350 MUST_SUCCEED (filesys_remove ("foo"));
351 MUST_SUCCEED (file_read (file, s2, sizeof s) == sizeof s);
352 MUST_SUCCEED (memcmp (s, s2, sizeof s) == 0);
353 MUST_SUCCEED (file_tell (file) == sizeof s);
354 MUST_SUCCEED (file_length (file) == sizeof s);
357 /* Make sure file is deleted. */
358 MUST_SUCCEED ((file = filesys_open ("foo")) == NULL);
361 printf ("filesys: self test ok\n");
364 /* Formats the filesystem. */
368 struct bitmap *free_map;
369 struct inode *map_inode, *dir_inode;
372 printf ("Formatting filesystem...");
374 /* Create the initial bitmap and reserve sectors for the
375 free map and root directory inodes. */
376 free_map = bitmap_create (disk_size (filesys_disk));
377 if (free_map == NULL)
378 PANIC ("bitmap creation failed--disk is too large");
379 bitmap_mark (free_map, FREE_MAP_SECTOR);
380 bitmap_mark (free_map, ROOT_DIR_SECTOR);
382 /* Allocate data sector(s) for the free map file
383 and write its inode to disk. */
384 map_inode = inode_create (free_map, FREE_MAP_SECTOR,
385 bitmap_file_size (free_map));
386 if (map_inode == NULL)
387 PANIC ("free map creation failed--disk is too large");
388 inode_commit (map_inode);
389 inode_close (map_inode);
391 /* Allocate data sector(s) for the root directory file
392 and write its inodes to disk. */
393 dir_inode = inode_create (free_map, ROOT_DIR_SECTOR,
394 dir_size (NUM_DIR_ENTRIES));
395 if (dir_inode == NULL)
396 PANIC ("root directory creation failed");
397 inode_commit (dir_inode);
398 inode_close (dir_inode);
400 /* Write out the free map now that we have space reserved
402 free_map_file = file_open (FREE_MAP_SECTOR);
403 if (free_map_file == NULL)
404 PANIC ("can't open free map file");
405 bitmap_write (free_map, free_map_file);
406 bitmap_destroy (free_map);
407 file_close (free_map_file);
409 /* Write out the root directory in the same way. */
410 root_dir_file = file_open (ROOT_DIR_SECTOR);
411 if (root_dir_file == NULL)
412 PANIC ("can't open root directory");
413 dir = dir_create (NUM_DIR_ENTRIES);
415 PANIC ("can't initialize root directory");
416 dir_write (dir, root_dir_file);
418 file_close (root_dir_file);
423 /* If SUCCESS is false, panics with an error complaining about
426 must_succeed_function (int line_no, bool success)
429 PANIC ("filesys_self_test: operation failed on line %d", line_no);