+/* This file is derived from source code for the Nachos
+ instructional operating system. The Nachos copyright notice
+ is reproduced in full below. */
+
+/* Copyright (c) 1992-1996 The Regents of the University of California.
+ All rights reserved.
+
+ Permission to use, copy, modify, and distribute this software
+ and its documentation for any purpose, without fee, and
+ without written agreement is hereby granted, provided that the
+ above copyright notice and the following two paragraphs appear
+ in all copies of this software.
+
+ IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO
+ ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
+ CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE
+ AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA
+ HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+ THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY
+ WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS"
+ BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
+ PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR
+ MODIFICATIONS.
+*/
+
#include "filesys.h"
#include "bitmap.h"
#include "debug.h"
#include "filehdr.h"
#include "lib.h"
-#define FREE_MAP_SECTOR 0
-#define ROOT_DIR_SECTOR 1
+/* Filesystem.
-#define NUM_DIR_ENTRIES 10
-#define ROOT_DIR_FILE_SIZE (sizeof (struct dir_entry) * NUM_DIR_ENTRIES)
+ The filesystem consists of a set of files. Each file has a
+ header, represented by struct filehdr, that is stored by
+ itself in a single sector (see filehdr.h). The header
+ contains the file's length in bytes and an array that lists
+ the sector numbers for the file's contents.
-struct disk *filesys_disk;
+ Two files are special. The first special file is the free
+ map, whose header is always stored in sector 0
+ (FREE_MAP_SECTOR). The free map stores a bitmap (see
+ lib/bitmap.h) that contains one bit for each sector on the
+ disk. Each bit that corresponds to a sector within a file is
+ set to true, and the other bits, which are not part of any
+ file, are set to false.
-static struct file free_map_file, root_dir_file;
+ The second special file is the root directory, whose header is
+ always stored in sector 1 (ROOT_DIR_SECTOR). The root
+ directory file stores an array of `struct dir_entry' (see
+ directory.h), each of which, if it is in use, associates a
+ filename with the sector of the file's header.
-static void
-do_format (void)
-{
- struct bitmap free_map;
- struct filehdr *map_hdr, *dir_hdr;
- struct dir dir;
+ The filesystem implemented here has the following limitations:
- printk ("Formatting filesystem...");
+ - No synchronization. Concurrent accesses will interfere
+ with one another.
- /* Create the initial bitmap and reserve sectors for the
- free map and root directory file headers. */
- if (!bitmap_init (&free_map, disk_size (filesys_disk)))
- PANIC ("bitmap creation failed--disk is too large");
- bitmap_mark (&free_map, FREE_MAP_SECTOR);
- bitmap_mark (&free_map, ROOT_DIR_SECTOR);
+ - File size is fixed at creation time. Because the root
+ directory is represented as a file, the number of files
+ that may be created is also limited.
- /* Allocate data sector(s) for the free map file
- and write its file header to disk. */
- map_hdr = filehdr_allocate (&free_map, bitmap_file_size (&free_map));
- if (map_hdr == NULL)
- PANIC ("free map creation failed--disk is too large");
- filehdr_write (map_hdr, FREE_MAP_SECTOR);
- filehdr_destroy (map_hdr);
+ - No indirect blocks. This limits maximum file size to the
+ number of sector pointers that fit in a single sector
+ times the size of a sector, or 126 * 512 == 63 kB given
+ 32-bit sizes and 512-byte sectors.
- /* Allocate data sector(s) for the root directory file
- and write its file header to disk. */
- dir_hdr = filehdr_allocate (&free_map, ROOT_DIR_FILE_SIZE);
- if (dir_hdr == NULL)
- PANIC ("root directory creation failed");
- filehdr_write (dir_hdr, ROOT_DIR_SECTOR);
- filehdr_destroy (dir_hdr);
+ - No nested subdirectories.
- /* Write out the free map now that we have space reserved
- for it. */
- if (!file_open (&free_map_file, FREE_MAP_SECTOR))
- PANIC ("can't open free map file");
- bitmap_write (&free_map, &free_map_file);
- bitmap_destroy (&free_map);
- file_close (&free_map_file);
+ - Filenames limited to 14 characters.
- /* Write out the root directory in the same way. */
- if (!file_open (&root_dir_file, ROOT_DIR_SECTOR))
- PANIC ("can't open root directory");
- if (!dir_init (&dir, NUM_DIR_ENTRIES))
- PANIC ("can't initialize root directory");
- dir_write (&dir, &root_dir_file);
- dir_destroy (&dir);
- file_close (&free_map_file);
+ - A system crash mid-operation may corrupt the disk in a way
+ that cannot be repaired automatically. No `fsck' tool is
+ provided in any case.
- printk ("done.\n");
-}
+ Note: for the purposes of the "user processes" assignment
+ (project 2), please treat all the code in the filesys
+ directory as a black box. No changes should be needed. For
+ that project, a single lock external to the filesystem code
+ suffices. */
+
+/* File header sectors for system files. */
+#define FREE_MAP_SECTOR 0 /* Free map file header sector. */
+#define ROOT_DIR_SECTOR 1 /* Root directory file header sector. */
+
+/* Root directory. */
+#define NUM_DIR_ENTRIES 10 /* Maximum number of directory entries. */
+#define ROOT_DIR_FILE_SIZE /* Root directory file size in bytes. */ \
+ (sizeof (struct dir_entry) * NUM_DIR_ENTRIES)
+
+/* The disk that contains the filesystem. */
+struct disk *filesys_disk;
+
+/* The free map and root directory files.
+ These files are opened by filesys_init() and never closed. */
+static struct file free_map_file, root_dir_file;
+
+static void do_format (void);
+/* Initializes the filesystem module.
+ If FORMAT is true, reformats the filesystem. */
void
filesys_init (bool format)
{
PANIC ("can't open root dir file");
}
+/* Creates a file named NAME with the given INITIAL_SIZE.
+ Returns true if successful, false otherwise.
+ Fails if a file named NAME already exists,
+ or if internal memory allocation fails. */
bool
filesys_create (const char *name, off_t initial_size)
{
return success;
}
+/* Opens a file named NAME and initializes FILE for usage with
+ the file_*() functions declared in file.h.
+ Returns true if successful, false on failure.
+ Fails if no file named NAME exists,
+ or if an internal memory allocation fails. */
bool
filesys_open (const char *name, struct file *file)
{
return success;
}
+/* Deletes the file named NAME.
+ Returns true if successful, false on failure.
+ Fails if no file named NAME exists,
+ or if an internal memory allocation fails. */
bool
filesys_remove (const char *name)
{
return success;
}
+/* Prints a list of files in the filesystem to the system
+ console.
+ Returns true if successful, false on failure,
+ which occurs only if an internal memory allocation fails. */
bool
filesys_list (void)
{
return true;
}
+/* Dumps the filesystem state to the system console,
+ including the free map, the list of files, and file contents.
+ Returns true if successful, false on failure,
+ which occurs only if an internal memory allocation fails. */
bool
filesys_dump (void)
{
return true;
}
-static void must_succeed_function (int, int) NO_INLINE;
-
-static void
-must_succeed_function (int line_no, int success)
-{
- if (!success)
- PANIC ("filesys_self_test: operation failed on line %d", line_no);
-}
-
+static void must_succeed_function (int, bool) NO_INLINE;
#define MUST_SUCCEED(EXPR) must_succeed_function (__LINE__, EXPR)
+/* Performs basic sanity checks on the filesystem.
+ The filesystem should not contain a file named `foo' when
+ called. */
void
filesys_self_test (void)
{
printk ("filesys: self test ok\n");
}
+\f
+/* Formats the filesystem. */
+static void
+do_format (void)
+{
+ struct bitmap free_map;
+ struct filehdr *map_hdr, *dir_hdr;
+ struct dir dir;
+
+ printk ("Formatting filesystem...");
+
+ /* Create the initial bitmap and reserve sectors for the
+ free map and root directory file headers. */
+ if (!bitmap_init (&free_map, disk_size (filesys_disk)))
+ PANIC ("bitmap creation failed--disk is too large");
+ bitmap_mark (&free_map, FREE_MAP_SECTOR);
+ bitmap_mark (&free_map, ROOT_DIR_SECTOR);
+
+ /* Allocate data sector(s) for the free map file
+ and write its file header to disk. */
+ map_hdr = filehdr_allocate (&free_map, bitmap_file_size (&free_map));
+ if (map_hdr == NULL)
+ PANIC ("free map creation failed--disk is too large");
+ filehdr_write (map_hdr, FREE_MAP_SECTOR);
+ filehdr_destroy (map_hdr);
+
+ /* Allocate data sector(s) for the root directory file
+ and write its file header to disk. */
+ dir_hdr = filehdr_allocate (&free_map, ROOT_DIR_FILE_SIZE);
+ if (dir_hdr == NULL)
+ PANIC ("root directory creation failed");
+ filehdr_write (dir_hdr, ROOT_DIR_SECTOR);
+ filehdr_destroy (dir_hdr);
+
+ /* Write out the free map now that we have space reserved
+ for it. */
+ if (!file_open (&free_map_file, FREE_MAP_SECTOR))
+ PANIC ("can't open free map file");
+ bitmap_write (&free_map, &free_map_file);
+ bitmap_destroy (&free_map);
+ file_close (&free_map_file);
+
+ /* Write out the root directory in the same way. */
+ if (!file_open (&root_dir_file, ROOT_DIR_SECTOR))
+ PANIC ("can't open root directory");
+ if (!dir_init (&dir, NUM_DIR_ENTRIES))
+ PANIC ("can't initialize root directory");
+ dir_write (&dir, &root_dir_file);
+ dir_destroy (&dir);
+ file_close (&free_map_file);
+
+ printk ("done.\n");
+}
+
+/* If SUCCESS is false, panics with an error complaining about
+ LINE_NO. */
+static void
+must_succeed_function (int line_no, bool success)
+{
+ if (!success)
+ PANIC ("filesys_self_test: operation failed on line %d", line_no);
+}
projects / pintos-anon / blobdiff