Require support for . and ...
Add inumber system call, so getcwd can be implemented,
and inode_get_inumber() function.
Implement these features in the reference solution.
Add "pwd" example program and require explanation of it in design
document.
Implement "cd" in shell.
Add -l option to "ls" example program.
Describe interpretation of unusual file names.
Remove filesys_self_test().
Update TODO.
Update the existing system calls so that, anywhere a file name is
provided by the caller, an absolute or relative path name may used.
The directory separator character is forward slash (@samp{/}).
-You may support @file{.} and @file{..} for a small amount of extra
-credit.
+You must also support special file names @file{.} and @file{..}, which
+have the same meanings as they do in Unix.
Update the @code{remove} system call so that it can delete empty
-directories in addition to regular files. Directories can only be
-deleted if they do not contain any files or subdirectories.
+directories in addition to regular files. Directories may only be
+deleted if they do not contain any files or subdirectories (other than
+@file{.} and @file{..}).
Update the @code{open} system call so that it can also open directories.
-Passing @file{.} as the argument to @code{open} must open the current
-directory, regardless of whether @file{.} and @file{..} are fully
-implemented. Of the existing system calls, only @code{close} needs to
-accept a file descriptor for a directory.
+Of the existing system calls, only @code{close} needs to accept a file
+descriptor for a directory.
Implement the following new system calls:
bytes, and returns true. If no entries are left in the directory,
returns false.
-@file{.} and @file{..} should not be returned by @code{readdir},
-regardless of whether they are implemented.
+@file{.} and @file{..} should not be returned by @code{readdir}.
If the directory changes while it is open, then it is acceptable for
some entries not to be read at all or to be read multiple times.
false if it represents an ordinary file.
@end deftypefn
+@deftypefn {System Call} int inumber (int @var{fd})
+Returns the @dfn{inode number} of the inode associated with @var{fd}.
+Applicable to file descriptors for both files and directories.
+
+An inode number persistently identifies a file or directory. It is
+unique during the file's existence. In Pintos, the sector number of the
+inode is suitable for use as an inode number.
+@end deftypefn
+
We have provided @command{ls} and @command{mkdir} user programs, which
-are straightforward once the above syscalls are implemented. The
-@command{shell} program implements @command{cd} internally.
+are straightforward once the above syscalls are implemented.
+We have also provided @command{pwd}, which is not so straightforward.
+The @command{shell} program implements @command{cd} internally.
The @code{pintos} @option{put} and @option{get} commands should now
accept full path names, assuming that the directories used in the
-paths have already been created. This should not require any extra
-effort on your part.
+paths have already been created. This should not require any significant
+extra effort on your part.
@node Buffer Cache
@subsection Buffer Cache
30 files changed, 2721 insertions(+), 286 deletions(-)
@end verbatim
-@item What extra credit opportunities are available?
-
-You may implement Unix-style support for @file{.} and @file{..} in
-relative paths in their projects.
-
-You may submit with VM enabled.
-
@item Can @code{DISK_SECTOR_SIZE} change?
No, @code{DISK_SECTOR_SIZE} is fixed at 512. This is a fixed property
@subsection Subdirectories FAQ
@table @b
-@item How should a file name like @samp{//a//b} be interpreted?
+@item How should a file name like @samp{a//b} be interpreted?
Multiple consecutive slashes are equivalent to a single slash, so this
-file name is the same as @samp{/a/b}.
+file name is the same as @samp{a/b}.
@item How about a file name like @samp{/../x}?
-If you don't implement @file{.} and @file{..}, then this is not a
-special case. If you do, then it is equivalent to @samp{/x}. That is,
-the root directory is its own parent.
+The root directory is its own parent, so it is equivalent to @samp{/x}.
+
+@item How should a file name that ends in @samp{/} be treated?
+
+Most Unix systems allow a slash at the end of the name for a directory,
+and reject other names that end in slashes. We will allow this
+behavior, as well as simply rejecting a name that ends in a slash.
@end table
@node Buffer Cache FAQ
>> Describe your code for traversing a user-specified path. How do
>> traversals of absolute and relative paths differ?
+>> Look over "pwd.c" in src/examples. Briefly explain how it
+>> determines the present working directory.
+
---- SYNCHRONIZATION ----
>> How do you prevent races on directory entries? For example, only one
mcat
mcp
mkdir
+pwd
rm
shell
bubsort
# Test programs to compile, and a list of sources for each.
# To add a new test, put its name on the PROGS list
# and then add a name_SRC line that lists its source files.
-PROGS = cat cmp cp echo halt hex-dump ls mcat mcp mkdir rm shell \
+PROGS = cat cmp cp echo halt hex-dump ls mcat mcp mkdir pwd rm shell \
bubsort insult lineup matmult recursor
+# Should work from project 2 onward.
cat_SRC = cat.c
cmp_SRC = cmp.c
cp_SRC = cp.c
echo_SRC = echo.c
halt_SRC = halt.c
hex-dump_SRC = hex-dump.c
+insult_SRC = insult.c
+lineup_SRC = lineup.c
ls_SRC = ls.c
-mcat_SRC = mcat.c
-mcp_SRC = mcp.c
-mkdir_SRC = mkdir.c
+recursor_SRC = recursor.c
rm_SRC = rm.c
-shell_SRC = shell.c
+# Should work in project 3; also in project 4 if VM is included.
bubsort_SRC = bubsort.c
-insult_SRC = insult.c
-lineup_SRC = lineup.c
matmult_SRC = matmult.c
-recursor_SRC = recursor.c
+mcat_SRC = mcat.c
+mcp_SRC = mcp.c
+
+# Should work in project 4.
+mkdir_SRC = mkdir.c
+pwd_SRC = pwd.c
+shell_SRC = shell.c
include $(SRCDIR)/Make.config
include $(SRCDIR)/Makefile.userprog
named.
By default, only the name of each file is printed. If "-l" is
- given as the first argument, the type and size of each file is
- also printed. */
+ given as the first argument, the type, size, and inumber of
+ each file is also printed. This won't work until project 4. */
#include <syscall.h>
#include <stdio.h>
if (isdir (dir_fd))
{
char name[READDIR_MAX_LEN];
- printf ("%s:\n", dir);
+
+ printf ("%s", dir);
+ if (verbose)
+ printf (" (inumber %d)", inumber (dir_fd));
+ printf (":\n");
+
while (readdir (dir_fd, name))
{
printf ("%s", name);
char full_name[128];
int entry_fd;
- if (strcmp (dir, "."))
- snprintf (full_name, sizeof full_name, "%s/%s", dir, name);
- else
- {
- /* This is a special case for implementations
- that don't fully understand . and .. */
- strlcpy (full_name, name, sizeof full_name);
- }
+ snprintf (full_name, sizeof full_name, "%s/%s", dir, name);
entry_fd = open (full_name);
printf (": ");
printf ("directory");
else
printf ("%d-byte file", filesize (entry_fd));
+ printf (", inumber %d", inumber (entry_fd));
}
else
printf ("open failed");
--- /dev/null
+/* pwd.c
+
+ Prints the absolute name of the present working directory. */
+
+#include <syscall.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+static bool getcwd (char *cwd, size_t cwd_size);
+
+int
+main (void)
+{
+ char cwd[128];
+ if (getcwd (cwd, sizeof cwd))
+ {
+ printf ("%s\n", cwd);
+ return 0;
+ }
+ else
+ {
+ printf ("error\n");
+ return 1;
+ }
+}
+\f
+/* Stores the inode number for FILE_NAME in *INUM.
+ Returns true if successful, false if the file could not be
+ opened. */
+static bool
+get_inumber (const char *file_name, int *inum)
+{
+ int fd = open (file_name);
+ if (fd >= 0)
+ {
+ *inum = inumber (fd);
+ close (fd);
+ return true;
+ }
+ else
+ return false;
+}
+
+/* Prepends PREFIX to the characters stored in the final *DST_LEN
+ bytes of the DST_SIZE-byte buffer that starts at DST.
+ Returns true if successful, false if adding that many
+ characters, plus a null terminator, would overflow the buffer.
+ (No null terminator is actually added or depended upon, but
+ its space is accounted for.) */
+static bool
+prepend (const char *prefix,
+ char *dst, size_t *dst_len, size_t dst_size)
+{
+ size_t prefix_len = strlen (prefix);
+ if (prefix_len + *dst_len + 1 <= dst_size)
+ {
+ *dst_len += prefix_len;
+ memcpy ((dst + dst_size) - *dst_len, prefix, prefix_len);
+ return true;
+ }
+ else
+ return false;
+}
+
+/* Stores the current working directory, as a null-terminated
+ string, in the CWD_SIZE bytes in CWD.
+ Returns true if successful, false on error. Errors include
+ system errors, directory trees deeper than MAX_LEVEL levels,
+ and insufficient space in CWD. */
+static bool
+getcwd (char *cwd, size_t cwd_size)
+{
+ size_t cwd_len = 0;
+
+#define MAX_LEVEL 20
+ char name[MAX_LEVEL * 3 + 1 + READDIR_MAX_LEN + 1];
+ char *namep;
+
+ int child_inum;
+
+ /* Make sure there's enough space for at least "/". */
+ if (cwd_size < 2)
+ return false;
+
+ /* Get inumber for current directory. */
+ if (!get_inumber (".", &child_inum))
+ return false;
+
+ namep = name;
+ for (;;)
+ {
+ int parent_inum, parent_fd;
+
+ /* Compose "../../../..", etc., in NAME. */
+ if ((namep - name) > MAX_LEVEL * 3)
+ return false;
+ *namep++ = '.';
+ *namep++ = '.';
+ *namep = '\0';
+
+ /* Open directory. */
+ parent_fd = open (name);
+ if (parent_fd < 0)
+ return false;
+ *namep++ = '/';
+
+ /* If parent and child have the same inumber,
+ then we've arrived at the root. */
+ parent_inum = inumber (parent_fd);
+ if (parent_inum == child_inum)
+ break;
+
+ /* Find name of file in parent directory with the child's
+ inumber. */
+ for (;;)
+ {
+ int test_inum;
+ if (!readdir (parent_fd, namep) || !get_inumber (name, &test_inum))
+ {
+ close (parent_fd);
+ return false;
+ }
+ if (test_inum == child_inum)
+ break;
+ }
+ close (parent_fd);
+
+ /* Prepend "/name" to CWD. */
+ if (!prepend (namep - 1, cwd, &cwd_len, cwd_size))
+ return false;
+
+ /* Move up. */
+ child_inum = parent_inum;
+ }
+
+ /* Finalize CWD. */
+ if (cwd_len > 0)
+ {
+ /* Move the string to the beginning of CWD,
+ and null-terminate it. */
+ memmove (cwd, (cwd + cwd_size) - cwd_len, cwd_len);
+ cwd[cwd_len] = '\0';
+ }
+ else
+ {
+ /* Special case for the root. */
+ strlcpy (cwd, "/", cwd_size);
+ }
+
+ return true;
+}
return success;
}
\f
-static void must_succeed_function (int, bool) NO_INLINE;
-#define MUST_SUCCEED(EXPR) must_succeed_function (__LINE__, EXPR)
-
-/* Performs basic sanity checks on the file system.
- The file system should not contain a file named `foo' when
- called. */
-void
-filesys_self_test (void)
-{
- static const char s[] = "This is a test string.";
- static const char zeros[sizeof s] = {0};
- struct file *file;
- char s2[sizeof s];
- int i;
-
- filesys_remove ("foo");
- for (i = 0; i < 2; i++)
- {
- /* Create file and check that it contains zeros
- throughout the created length. */
- MUST_SUCCEED (filesys_create ("foo", sizeof s));
- MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
- MUST_SUCCEED (file_read (file, s2, sizeof s2) == sizeof s2);
- MUST_SUCCEED (memcmp (s2, zeros, sizeof s) == 0);
- MUST_SUCCEED (file_tell (file) == sizeof s);
- MUST_SUCCEED (file_length (file) == sizeof s);
- file_close (file);
-
- /* Reopen file and write to it. */
- MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
- MUST_SUCCEED (file_write (file, s, sizeof s) == sizeof s);
- MUST_SUCCEED (file_tell (file) == sizeof s);
- MUST_SUCCEED (file_length (file) == sizeof s);
- file_close (file);
-
- /* Reopen file and verify that it reads back correctly.
- Delete file while open to check proper semantics. */
- MUST_SUCCEED ((file = filesys_open ("foo")) != NULL);
- MUST_SUCCEED (filesys_remove ("foo"));
- MUST_SUCCEED (filesys_open ("foo") == NULL);
- MUST_SUCCEED (file_read (file, s2, sizeof s) == sizeof s);
- MUST_SUCCEED (memcmp (s, s2, sizeof s) == 0);
- MUST_SUCCEED (file_tell (file) == sizeof s);
- MUST_SUCCEED (file_length (file) == sizeof s);
- file_close (file);
- }
-
- printf ("filesys: self test ok\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);
-}
-\f
/* Formats the file system. */
static void
do_format (void)
struct file *filesys_open (const char *name);
bool filesys_remove (const char *name);
-void filesys_self_test (void);
-
#endif /* filesys/filesys.h */
/* Reopens and returns INODE. */
struct inode *
-inode_reopen (struct inode *inode)
+inode_reopen (struct inode *inode)
{
- if (inode != NULL)
+ if (inode != NULL)
inode->open_cnt++;
return inode;
}
+/* Returns INODE's inode number. */
+disk_sector_t
+inode_get_inumber (const struct inode *inode)
+{
+ return inode->sector;
+}
+
/* Closes INODE and writes it to disk.
If this was the last reference to INODE, frees its memory.
If INODE was also a removed inode, frees its blocks. */
bool inode_create (disk_sector_t, off_t);
struct inode *inode_open (disk_sector_t);
struct inode *inode_reopen (struct inode *);
+disk_sector_t inode_get_inumber (const struct inode *);
void inode_close (struct inode *);
void inode_remove (struct inode *);
off_t inode_read_at (struct inode *, void *, off_t size, off_t offset);
SYS_CHDIR, /* Change the current directory. */
SYS_MKDIR, /* Create a directory. */
SYS_READDIR, /* Reads a directory entry. */
- SYS_ISDIR /* Tests if a fd represents a directory. */
+ SYS_ISDIR, /* Tests if a fd represents a directory. */
+ SYS_INUMBER /* Returns the inode number for a fd. */
};
#endif /* lib/syscall-nr.h */
{
return syscall1 (SYS_ISDIR, fd);
}
+
+int
+inumber (int fd)
+{
+ return syscall1 (SYS_INUMBER, fd);
+}
bool mkdir (const char *dir);
bool readdir (int fd, char name[READDIR_MAX_LEN + 1]);
bool isdir (int fd);
+int inumber (int fd);
#endif /* lib/user/syscall.h */
+examples
filesys
list
p1
projects / pintos-anon / commitdiff