generalize resolve_directory into resolve_path, fix mkdir, cd, update rm, create, add rmdir

config.h

@@ -26,6 +26,7 @@
 #define FS_MAX_PATH_LEN 512
 #define FS_MAX_OPEN_FD 32
 #define FS_MAX_FNAME_LEN 11
+#define FS_MAX_DIRECTORY_DEPTH 512
 
 
 #endif

inc/fs.h

@@ -1,5 +1,7 @@
 #include "config.h"
 
+#define FOLLOW_LAST_SYMLINK 0x1
+
 enum fs_filetype {
 	REGULAR,
 	DIRECTORY
@@ -46,6 +48,13 @@ struct fs_file_description {
 	unsigned int rw_offset;
 };
 
+struct resolved_path {
+	int target_inode_ptr;
+	int parent_inode_ptr;
+	char target_fname[FS_MAX_FNAME_LEN+1];
+	char parent_fname[FS_MAX_FNAME_LEN+1];
+};
+
 char *fs_get_cwd(void);
 
 int fs_create(void *d);
@@ -61,6 +70,9 @@ int fs_seek(void *d);
 int fs_read(void *d);
 int fs_write(void *d);
 int fs_close(void *d);
+int fs_mkdir(void *d);
+int fs_rmdir(void *d);
+int fs_cd(void *d);
 int fs_truncate(void *d);
 int fs_allow_write(void *d);
 int fs_prohibit_write(void *d);

inc/print.h

@@ -9,68 +9,58 @@
 #include "color.h"
 
 #if DEBUG == 1
-	#define pr(...) { printf("[%s:%d] ", __FILE__, __LINE__); printf(__VA_ARGS__); }
+	#define pr(...) do { printf("[%s:%d] ", __FILE__, __LINE__); printf(__VA_ARGS__); } while (0)
 #else
-	#define pr(...) {}
+	#define pr(...)
 #endif
 
 
 #if ENABLE_STDOUT == 1
-	#define pr_stdout(...) { printf(__VA_ARGS__); }
-	#define write_stdout(data, size) { write(1, (data), (size)); }
+	#define pr_stdout(...) do { printf(__VA_ARGS__); } while (0)
+	#define write_stdout(data, size) do { write(1, (data), (size)); } while (0)
 #else
-	#define pr_stdout(...) {}
-	#define write_stdout(data, size) {}
+	#define pr_stdout(...)
+	#define write_stdout(data, size)
+#endif
+
+
+#if LOG_LEVEL >= 0
+	#if ENABLE_FILE_LINE_IN_OTHER_PR == 1
+		#define pr_generic(color, prefix, ...) do { \
+			printf(color "[%s:%d] " prefix, __FILE__, __LINE__); \
+			printf(__VA_ARGS__); \
+			printf(COLOR_RESET); \
+		} while (0)
+	#else
+		#define pr_generic(color, prefix, ...) do { \
+			printf(color prefix); \
+			printf(__VA_ARGS__); \
+			printf(COLOR_RESET); \
+		} while (0)
+	#endif
+#else
+	#define pr_generic(color, prefix, ...)
 #endif
 
 
 #if LOG_LEVEL >= 2
-	#if ENABLE_FILE_LINE_IN_OTHER_PR == 1
-		#define pr_err(...) { \
-			printf(COLOR_RED "[%s:%d] Error: ", __FILE__, __LINE__); \
-			printf(__VA_ARGS__); \
-			printf(COLOR_RESET); \
-		}
-	#else
-		#define pr_err(...) { \
-			printf(COLOR_RED "Error: "); \
-			printf(__VA_ARGS__); \
-			printf(COLOR_RESET);\
-		}
-	#endif
+	#define pr_err(...) pr_generic(COLOR_RED, "Error: ", __VA_ARGS__)
 #else
-	#define pr_err(...) {}
+	#define pr_err(...)
 #endif
 
+
 #if LOG_LEVEL >= 3
-	#if ENABLE_FILE_LINE_IN_OTHER_PR == 1
-		#define pr_warn(...) { \
-			printf(COLOR_YELLOW "[%s:%d] Warning: ", __FILE__, __LINE__); \
-			printf(__VA_ARGS__); \
-			printf(COLOR_RESET); \
-		}
-	#else
-		#define pr_warn(...) { \
-			printf(COLOR_YELLOW "Warning: "); \
-			printf(__VA_ARGS__); \
-			printf(COLOR_RESET); \
-		}
-	#endif
+	#define pr_warn(...) pr_generic(COLOR_YELLOW, "Warning: ", __VA_ARGS__)
 #else
-	#define pr_warn(...) {}
+	#define pr_warn(...)
 #endif
 
+
 #if LOG_LEVEL >= 4
-	#if ENABLE_FILE_LINE_IN_OTHER_PR == 1
-		#define pr_info(...) { \
-			printf("[%s:%d] Info: ", __FILE__, __LINE__); \
-			printf(__VA_ARGS__); \
-		}
-	#else
-		#define pr_info(...) { printf("Info: "); printf(__VA_ARGS__); }
-	#endif
+	#define pr_info(...) pr_generic(COLOR_RESET, "Info: ", __VA_ARGS__)
 #else
-	#define pr_info(...) {}
+	#define pr_info(...)
 #endif
 
 

src/cli.c

@@ -26,6 +26,10 @@ static const struct CliCommandEntry cmd[] = {
 	{"write", 2, (enum CliArgType[]) {INT, STR}, fs_write},
 	{"close", 1, (enum CliArgType[]) {INT}, fs_close},
 
+	{"mkdir", 1, (enum CliArgType[]) {STR}, fs_mkdir},
+	{"rmdir", 1, (enum CliArgType[]) {STR}, fs_rmdir},
+	{"cd", 1, (enum CliArgType[]) {STR}, fs_cd},
+
 	// custom commands
 	{"use", 1, (enum CliArgType[]) {STR}, fs_use},
 	{"la", 0, NULL, fs_la},
@@ -68,8 +72,8 @@ static char **tokenize_line(char *line, ssize_t result)
 	unsigned int i, t, l;
 	for (
 		i = 0, t = 0, l = 0;
-		i < CLI_MAX_LINE_LENGTH,
-		t <= CLI_MAX_ACCEPTED_ARGS,
+		i < CLI_MAX_LINE_LENGTH &&
+		t <= CLI_MAX_ACCEPTED_ARGS &&
 		l < CLI_MAX_TOKEN_LENGTH;
 		i++
 	) {
@@ -204,9 +208,9 @@ unsigned int cli_poll_process_next(void)
 		fputs(fs_get_cwd(), stdout);
 
 		if (fs_get_cwd()[0]) {
-			fputs(" $ ", stdout);
+			printf(" $ ");
 		} else {
-			fputs("$ ", stdout);
+			printf("$ ");
 		}
 
 		size_t buf_size = 0;

src/fs.c

@@ -23,6 +23,8 @@ static unsigned int fs_cwd_inode_ptr;
 
 static struct fs_file_description fs_file_descriptions[FS_MAX_OPEN_FD];
 
+static int extract_basename(char *path, char *name);
+
 
 static int read_block(unsigned int block_no, void *data)
 {
@@ -451,7 +453,7 @@ static int fs_find_free_directory_record(unsigned int dir_inode_ptr)
 		read_block(dir.blocks[i], (void *) &r);
 
 		for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++, found_block_no++) {
-			if (r[j].inode_no)
+			if (r[j].fname)
 				continue;
 
 			if (found_block_no >= fsh.max_inode_count)
@@ -484,7 +486,7 @@ static int fs_find_free_directory_record(unsigned int dir_inode_ptr)
 			read_block(ext.blocks[i], (void *) &r);
 
 			for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++, found_block_no++) {
-				if (r[j].inode_no)
+				if (r[j].fname)
 					continue;
 
 				if (found_block_no >= fsh.max_inode_count)
@@ -503,7 +505,7 @@ static int fs_find_free_directory_record(unsigned int dir_inode_ptr)
 
 static int *find_filename_in_directory(unsigned int dir_inode_ptr, char *fname)
 {
-	int dir_inode = read_inode_ptr(fs_cwd_inode_ptr);
+	int dir_inode = read_inode_ptr(dir_inode_ptr);
 
 	struct fs_inode dir;
 	read_block(dir_inode, (void *) &dir);
@@ -516,7 +518,7 @@ static int *find_filename_in_directory(unsigned int dir_inode_ptr, char *fname)
 			read_block(dir.blocks[i], (void *) &recs);
 
 			for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-				if (!recs[k].inode_no)
+				if (!recs[k].fname)
 					continue;
 
 				if (strcmp(fname, recs[k].fname))
@@ -547,7 +549,7 @@ static int *find_filename_in_directory(unsigned int dir_inode_ptr, char *fname)
 				read_block(ext.blocks[i], (void *) &recs);
 
 				for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-					if (!recs[k].inode_no)
+					if (!recs[k].fname)
 						continue;
 
 					if (strcmp(fname, recs[k].fname))
@@ -567,6 +569,21 @@ static int *find_filename_in_directory(unsigned int dir_inode_ptr, char *fname)
 	return NULL;
 }
 
+static int find_fname_in_directory(unsigned int dir_inode_ptr, char *fname)
+{
+	int *r = find_filename_in_directory(dir_inode_ptr, fname);
+	int res;
+
+	if (r) {
+		res = r[2];
+		free(r);
+	} else {
+		res = -1;
+	}
+
+	return res;
+}
+
 static int inode_is_referenced(unsigned int inode)
 {
 	struct fs_inode f;
@@ -620,7 +637,7 @@ static int fs_add_fname_to_directory(unsigned int dir_inode_ptr, unsigned int ta
 		if (r) {
 			free(r);
 			pr_err("filename '%s' already exists\n", fname);
-			return 0;
+			return -1;
 		}
 	}
 
@@ -773,13 +790,13 @@ static void fs_remove_fname_from_directory_removal(struct fs_directory_record *r
 
 	// decrement ref_count
 	struct fs_inode f;
-	read_block(read_inode_ptr(recs[k].inode_no), (void *) &f);
+	read_block(read_inode_ptr(recs[k].inode_no), &f);
 	f.ref_count--;
-	write_block(read_inode_ptr(recs[k].inode_no), (void *) &f);
+	write_block(read_inode_ptr(recs[k].inode_no), &f);
 
 	// clear directory record inode_ptr
-	recs[k].inode_no = 0;
-	write_block(dir_block_addr, (void *) recs);
+	recs[k].fname[0] = 0;
+	write_block(dir_block_addr, recs);
 
 	// if it drops to zero, nullify inode_ptr pointing to this inode
 	if (f.ref_count)
@@ -807,11 +824,8 @@ static void fs_remove_fname_from_directory_removal(struct fs_directory_record *r
 
 static int fs_remove_fname_from_directory(unsigned int dir_inode_ptr, char *fname)
 {
-	// find directory record with this fname
-	int dir_inode = read_inode_ptr(fs_cwd_inode_ptr);
-
 	struct fs_inode dir;
-	read_block(dir_inode, (void *) &dir);
+	read_block(read_inode_ptr(dir_inode_ptr), &dir);
 
 	// list entries from base inode
 	for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE; i++) {
@@ -820,10 +834,10 @@ static int fs_remove_fname_from_directory(unsigned int dir_inode_ptr, char *fnam
 		if (!dir.blocks[i])
 			continue;
 
-		read_block(dir.blocks[i], (void *) &recs);
+		read_block(dir.blocks[i], &recs);
 
 		for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-			if (!recs[k].inode_no)
+			if (!recs[k].fname)
 				continue;
 
 			if (strcmp(fname, recs[k].fname))
@@ -860,7 +874,7 @@ static int fs_remove_fname_from_directory(unsigned int dir_inode_ptr, char *fnam
 			read_block(ext.blocks[i], (void *) &recs);
 
 			for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-				if (!recs[k].inode_no)
+				if (!recs[k].fname)
 					continue;
 
 				if (strcmp(fname, recs[k].fname))
@@ -884,6 +898,111 @@ fs_remove_fname_from_directory_finish:
 	return 0;
 }
 
+static void resolve_path(struct resolved_path *rp, char *path, unsigned int params)
+{
+	rp->parent_inode_ptr = -1;
+	rp->target_inode_ptr = -1;
+
+	int path_len = strlen(path);
+
+	if (!path_len) {
+		pr_err("no path specified\n");
+		return;
+	}
+
+	if (!strcmp(path, "/")) {
+		rp->parent_inode_ptr = 0;
+		rp->target_inode_ptr = 0;
+		strcpy(rp->parent_fname, "/");
+		strcpy(rp->target_fname, "/");
+		return;
+	}
+
+	char current_fname[FS_MAX_FNAME_LEN+1] = {};
+	int current_inode_ptr;
+	int i;
+
+	if (path[0] == '/') {
+		current_inode_ptr = 0;
+		rp->parent_inode_ptr = 0;
+		strcpy(current_fname, "/");
+		i = 1;
+	} else {
+		current_inode_ptr = fs_cwd_inode_ptr;
+		rp->parent_inode_ptr = fs_cwd_inode_ptr;
+		extract_basename(fs_cwd, current_fname);
+		i = 0;
+	}
+
+	char next_fname[FS_MAX_FNAME_LEN+1] = {};
+	int next_fname_ptr = 0;
+
+	for ( ; i < path_len; i++) {
+		if (path[i] != '/') {
+			next_fname[next_fname_ptr] = path[i];
+			next_fname_ptr++;
+			continue;
+		}
+
+		// path[i] == '/', trying to change current directory
+
+		if (!next_fname_ptr)
+			continue;
+
+		if (i+1 == path_len)
+			continue;
+
+		{
+			int res = find_fname_in_directory(current_inode_ptr, next_fname);
+			if (res < 0) {
+				pr_warn("directory '%s' does not exist\n", next_fname);
+				rp->parent_inode_ptr = -1;
+				break;
+			}
+
+			{
+				struct fs_inode d;
+				read_block(read_inode_ptr(res), &d);
+
+				if (d.ftype == REGULAR) {
+					pr_warn("'%s' is a regular file\n", next_fname);
+					rp->parent_inode_ptr = -1;
+					break;
+				}
+			}
+
+			pr("Found directory '%s'\n", next_fname);
+			current_inode_ptr = res;
+			rp->parent_inode_ptr = res;
+		}
+
+		next_fname_ptr = 0;
+		strcpy(current_fname, next_fname);
+		memset(next_fname, 0, FS_MAX_FNAME_LEN);
+	}
+
+	if (rp->parent_inode_ptr < 0) {
+		rp->target_inode_ptr = -1;
+		return;
+	}
+
+	strcpy(rp->parent_fname, current_fname);
+
+	{
+		int res = find_fname_in_directory(current_inode_ptr, next_fname);
+		if (res < 0) {
+			pr_warn("target fname '%s' does not exist\n", next_fname);
+			rp->target_inode_ptr = -1;
+		} else {
+			rp->target_inode_ptr = res;
+			strcpy(rp->target_fname, next_fname);
+		}
+	}
+
+	return;
+}
+
+
 int fs_open(void *d)
 {
 	char *fname = *((char **) d);
@@ -1353,24 +1472,32 @@ int fs_create(void *d)
 		return 0;
 	}
 
-	char *fname = *((char **) d);
-	int fname_len = strlen(fname);
-
+	char *path = *((char **) d);
 	{
-		// check if duplicate filename exists in current directory
-		int *r = find_filename_in_directory(fs_cwd_inode_ptr, fname);
-		if (r) {
-			free(r);
-			pr_err("filename '%s' already exists\n", fname);
+		int path_len = strlen(path);
+		if (path_len > FS_MAX_PATH_LEN) {
+			pr_err("path too long (%d > %d)\n",
+					path_len, FS_MAX_PATH_LEN);
 			return 0;
 		}
 	}
 
-	if (fname_len > FS_MAX_FNAME_LEN) {
-		pr_err("filename too long (%d > %d)\n", fname_len, FS_MAX_FNAME_LEN);
+	struct resolved_path rp;
+	resolve_path(&rp, path, 0);
+
+	if (rp.parent_inode_ptr < 0) {
+		pr_err("unable to create file: no such directory: '%s'\n", path);
 		return 0;
 	}
 
+	if (rp.target_inode_ptr >= 0) {
+		pr_err("file already exists: '%s'\n", rp.target_fname);
+		return 0;
+	}
+
+	char fname[FS_MAX_FNAME_LEN+1];
+	extract_basename(path, fname);
+
 	pr("Creating regular file '%s'\n", fname);
 
 	int inode_block_no = find_free_block();
@@ -1411,7 +1538,7 @@ int fs_create(void *d)
 	write_inode_ptr(inode_ptr_index, inode_block_no);
 
 	// add filename to current directory inode
-	fs_add_fname_to_directory(fs_cwd_inode_ptr, inode_ptr_index, fname);
+	fs_add_fname_to_directory(rp.parent_inode_ptr, inode_ptr_index, fname);
 
 	return 0;
 }
@@ -1522,6 +1649,379 @@ original_inode_ptr_found:
 	pr("Updated inode ref_count (%d -> %d)\n", f.ref_count-1, f.ref_count);
 }
 
+
+static int last_significant_slash_position(char *path, int path_len)
+{
+	int last_position = -1;
+
+	for (int i = 0; i < path_len; i++)
+		if ((path[i] == '/') && (i+1 != path_len))
+			last_position = i;
+
+	return last_position;
+}
+
+static int extract_basename(char *path, char *name)
+{
+	int path_len = strlen(path);
+
+	int lsp = last_significant_slash_position(path, path_len);
+	int fname_len = path_len - lsp - 1;
+
+	if (fname_len > FS_MAX_FNAME_LEN) {
+		pr_err("filename too long (%d > %d)",
+				fname_len, FS_MAX_FNAME_LEN);
+		return -1;
+	}
+
+	strcpy(name, &(path[lsp+1]));
+
+	return fname_len;
+}
+
+static void extract_parent_directory_path(char *path, char *parent_path)
+{
+	int path_len = strlen(path);
+	int lsp = last_significant_slash_position(path, path_len);
+	int parent_len = last_significant_slash_position(path, lsp-1);
+
+	if (parent_len > 1) {
+		memcpy(parent_path, path, parent_len-1);
+		parent_path[parent_len] = '\0';
+	} else {
+		strcpy(parent_path, "/");
+	}
+
+
+}
+
+int fs_mkdir(void *d)
+{
+	char *dirpath = *((char **)d);
+	int dirpath_len = strlen(dirpath);
+
+	if (dirpath_len > FS_MAX_PATH_LEN) {
+		pr_err("path too long ('%s', %d > %d)\n",
+				dirpath, dirpath_len, FS_MAX_FNAME_LEN);
+		return 0;
+	}
+
+	char dirname[FS_MAX_FNAME_LEN+1];
+	{
+		int res = extract_basename(dirpath, dirname);
+		if (res < 0) {
+			pr_err("failed to extract dirname from path '%s'\n",
+					dirpath);
+			return 0;
+		}
+	}
+	int dirname_len = strlen(dirname);
+
+	if (dirname_len > FS_MAX_FNAME_LEN) {
+		pr_err("directory name too long ('%s', %d > %d)\n",
+				dirname, dirname_len, FS_MAX_FNAME_LEN);
+		return 0;
+	}
+
+	struct resolved_path rp;
+	resolve_path(&rp, dirpath, 0);
+	if (rp.parent_inode_ptr < 0) {
+		pr_err("failed to find parent of '%s'\n", dirpath);
+		return 0;
+	} else if (rp.target_inode_ptr >= 0) {
+		pr_err("fname '%s' already exists in directory '%s'\n",
+				rp.target_fname, rp.parent_fname);
+		return 0;
+	}
+
+	int target_inode_ptr = find_free_inode_ptr();
+	if (!target_inode_ptr) {
+		pr_err("no free inode ptr\n");
+		return 0;
+	}
+
+	int target_inode_block = find_free_block();
+	if (!target_inode_block) {
+		pr_err("no space left on device\n");
+		return 0;
+	}
+
+	struct fs_inode dir;
+	memset(&dir, 0, sizeof(dir));
+
+	dir.ftype = DIRECTORY;
+	dir.ref_count = 1;
+
+	write_block(target_inode_block, &dir);
+	mark_used(target_inode_block);
+
+	write_inode_ptr(target_inode_ptr, target_inode_block);
+
+	if (fs_add_fname_to_directory(rp.parent_inode_ptr, target_inode_ptr, dirname) < 0) {
+		pr_err("failed to add record '%s' -> inode_ptr=%d to directory '%s' (inode_ptr=%d)\n",
+				dirname, target_inode_ptr, rp.parent_fname, rp.parent_inode_ptr);
+		return 0;
+	}
+
+	// add . and ..
+	fs_add_fname_to_directory(target_inode_ptr, target_inode_ptr, ".");
+	fs_add_fname_to_directory(target_inode_ptr, rp.parent_inode_ptr, "..");
+}
+
+
+static int count_active_directory_records(struct fs_inode *inode)
+{
+	int total_active_records = 0;
+
+	// base inode
+	for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE; i++) {
+		if (!inode->blocks[i])
+			continue;
+
+		struct fs_directory_record recs[DIRECTORY_RECORDS_PER_BLOCK];
+		read_block(inode->blocks[i], &recs);
+
+		for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++) {
+			if (!recs[j].fname[0])
+				continue;
+
+			if (!strcmp(recs[j].fname, "."))
+				continue;
+
+			if (!strcmp(recs[j].fname, ".."))
+				continue;
+
+			total_active_records++;
+		}
+	}
+
+	// inode extensions
+	unsigned int next_ext = inode->next_extension;
+	unsigned int curr_ext = 0;
+
+	struct fs_inode_extension ext;
+
+	while (next_ext) {
+		read_block(next_ext, &ext);
+		curr_ext = next_ext;
+		next_ext = ext.next_extension;
+
+		for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE_EXTENSION; i++) {
+			if (!ext.blocks[i])
+				continue;
+
+			struct fs_directory_record recs[DIRECTORY_RECORDS_PER_BLOCK];
+			read_block(ext.blocks[i], &recs);
+
+			for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++) {
+				if (!recs[j].fname[0])
+					continue;
+
+				if (!strcmp(recs[j].fname, "."))
+					continue;
+
+				if (!strcmp(recs[j].fname, ".."))
+					continue;
+
+				total_active_records++;
+			}
+		}
+	}
+
+	return total_active_records;
+}
+
+int fs_rmdir(void *d)
+{
+	char *dirpath = *((char **)d);
+	int dirpath_len = strlen(dirpath);
+
+	if (dirpath_len > FS_MAX_PATH_LEN) {
+		pr_err("path too long ('%s', %d > %d)\n",
+				dirpath, dirpath_len, FS_MAX_FNAME_LEN);
+		return 0;
+	}
+
+	struct resolved_path rp;
+	resolve_path(&rp, dirpath, 0);
+
+	if (rp.parent_inode_ptr < 0) {
+		pr_err("failed to find parent directory of '%s'\n", dirpath);
+		return 0;
+	} else if (rp.target_inode_ptr < 0) {
+		pr_err("no such file: '%s'\n", dirpath);
+		return 0;
+	} else if (!strcmp(rp.target_fname, ".")) {
+		pr_err("can not remove '.' from a directory\n");
+		return 0;
+	}
+
+	{
+		struct fs_inode i;
+		read_block(read_inode_ptr(rp.target_inode_ptr), &i);
+
+		if (i.ftype != DIRECTORY) {
+			pr_err("'%s' is not a directory\n", rp.target_fname);
+			return 0;
+		}
+
+		if (count_active_directory_records(&i)) {
+			pr_err("directory '%s' is not empty\n", rp.target_fname);
+			return 0;
+		}
+	}
+
+	fs_remove_fname_from_directory(rp.parent_inode_ptr, rp.target_fname);
+
+	return 0;
+}
+
+
+static int get_fname_by_inode_ptr(int dir_inode_ptr, int file_inode_ptr, char *name)
+{
+	struct fs_inode dir;
+	read_block(read_inode_ptr(dir_inode_ptr), &dir);
+
+	// search base inode
+	for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE; i++) {
+		struct fs_directory_record recs[DIRECTORY_RECORDS_PER_BLOCK];
+
+		if (!dir.blocks[i])
+			continue;
+
+		read_block(dir.blocks[i], &recs);
+
+		for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++) {
+			if (!recs[j].fname)
+				continue;
+
+			if (recs[j].inode_no != file_inode_ptr)
+				continue;
+
+			strcpy(name, recs[j].fname);
+			return 0;
+		}
+	}
+
+	// search inode extensions
+	unsigned int next_ext = dir.next_extension;
+	unsigned int curr_ext = 0;
+
+	struct fs_inode_extension ext;
+
+	while (next_ext) {
+		read_block(next_ext, &ext);
+		curr_ext = next_ext;
+		next_ext = ext.next_extension;
+
+		for (int i = 0; i < BLOCK_ADDRESSES_PER_INODE_EXTENSION; i++) {
+			struct fs_directory_record recs[DIRECTORY_RECORDS_PER_BLOCK];
+
+			if (!ext.blocks[i])
+				continue;
+
+			read_block(ext.blocks[i], &recs);
+
+			for (int j = 0; j < DIRECTORY_RECORDS_PER_BLOCK; j++) {
+				if (!recs[j].fname)
+					continue;
+
+				if (recs[j].inode_no != file_inode_ptr)
+					continue;
+
+				strcpy(name, recs[j].fname);
+				return 0;
+			}
+		}
+	}
+
+	pr_err("no such file (inode_ptr=%d)\n", file_inode_ptr);
+	return -1;
+}
+
+static int build_canonical_dir_path(char *path, int dir_inode_ptr)
+{
+	// build directory inode_ptr-based reverse path
+	int dir_inode_ptrs[FS_MAX_DIRECTORY_DEPTH];
+	int dir_inode_ptrs_len = 1;
+
+	dir_inode_ptrs[0] = dir_inode_ptr;
+
+	for ( ; dir_inode_ptrs_len < FS_MAX_DIRECTORY_DEPTH; dir_inode_ptrs_len++) {
+		// check if reached the root dir
+		if (!dir_inode_ptrs[dir_inode_ptrs_len-1])
+			break;
+
+		int *r = find_filename_in_directory(dir_inode_ptrs[dir_inode_ptrs_len-1], "..");
+
+		if (!r) {
+			pr_err("failed to find parent directory of inode_ptr=%d\n", dir_inode_ptrs[dir_inode_ptrs_len-1]);
+			return -1;
+		}
+
+		dir_inode_ptrs[dir_inode_ptrs_len] = r[2];
+		free(r);
+	}
+
+	// build string path based on inode_ptr list
+	memset(path, 0, sizeof(FS_MAX_PATH_LEN));
+
+	for (int i = dir_inode_ptrs_len - 2; i >= 0; i--) {
+		char fname[FS_MAX_FNAME_LEN+1];
+
+		if (get_fname_by_inode_ptr(dir_inode_ptrs[i+1], dir_inode_ptrs[i], fname) < 0) {
+			pr_err("failed to build canonical path\n");
+			return -1;
+		}
+
+		strcat(path, "/");
+		strcat(path, fname);
+	}
+
+	return 0;
+}
+
+int fs_cd(void *d)
+{
+	char *new_dir = *((char **)d);
+	int new_dir_len = strlen(new_dir);
+
+	if (new_dir_len > FS_MAX_PATH_LEN) {
+		pr_err("path too long (%d > %d)\n", new_dir_len, FS_MAX_PATH_LEN);
+		return 0;
+	}
+
+	struct resolved_path rp;
+	resolve_path(&rp, new_dir, FOLLOW_LAST_SYMLINK);
+
+	if (rp.parent_inode_ptr < 0) {
+		pr_err("failed to find parent of '%s' from '%s'\n", new_dir, fs_cwd);
+		return 0;
+	}
+
+	if (rp.target_inode_ptr < 0) {
+		pr_err("no such directory: '%s'\n", new_dir);
+		return 0;
+	}
+
+	char canonical_path[FS_MAX_PATH_LEN+1];
+	if (build_canonical_dir_path(canonical_path, rp.target_inode_ptr) < 0) {
+		pr_err("failed to build canonical path to '%s' (inode_ptr=%d)\n",
+				new_dir, rp.target_inode_ptr);
+		return 0;
+	}
+
+	if (!canonical_path[0])
+		canonical_path[0] = '/';
+
+	char *cpp = (char *) canonical_path;
+	fs_chdir(&cpp);
+	fs_cwd_inode_ptr = rp.target_inode_ptr;
+
+	return 0;
+}
+
+
 int fs_rm(void *d)
 {
 	if (!write_permitted) {
@@ -1529,12 +2029,36 @@ int fs_rm(void *d)
 		return 0;
 	}
 
-	char *fname = *((char **) d);
+	char *path = *((char **) d);
+	{
+		int path_len = strlen(path);
+		if (path_len > FS_MAX_PATH_LEN) {
+			pr_err("path too long (%d > %d)\n",
+					path_len, FS_MAX_PATH_LEN);
+			return 0;
+		}
+	}
 
-	if (fs_remove_fname_from_directory(fs_cwd_inode_ptr, fname) < 0) {
-		pr_err("failed to unlink '%s'\n", fname);
+	struct resolved_path rp;
+	resolve_path(&rp, path, 0);
+
+	if (rp.target_inode_ptr < 0) {
+		pr_err("file does not exist: '%s'\n", path);
+		return 0;
+	}
+
+	struct fs_inode i;
+	read_block(read_inode_ptr(rp.target_inode_ptr), &i);
+
+	if (i.ftype == DIRECTORY) {
+		pr_err("file '%s' is a directory\n", rp.target_fname);
+		return 0;
+	}
+
+	if (fs_remove_fname_from_directory(rp.parent_inode_ptr, rp.target_fname) < 0) {
+		pr_err("failed to unlink '%s'\n", rp.target_fname);
 	} else {
-		pr("Unlinked '%s'\n", fname);
+		pr("Unlinked '%s'\n", rp.target_fname);
 	}
 
 	return 0;
@@ -1561,7 +2085,7 @@ int fs_ls(void *d)
 		read_block(dir.blocks[i], (void *) &recs);
 
 		for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-			if (!recs[k].inode_no)
+			if (!recs[k].fname[0])
 				continue;
 
 			pr_stdout("%s -> inode_ptr=%d\n", recs[k].fname, recs[k].inode_no);
@@ -1584,7 +2108,7 @@ int fs_ls(void *d)
 			read_block(ext.blocks[i], (void *) &recs);
 
 			for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-				if (!recs[k].inode_no)
+				if (!recs[k].fname[0])
 					continue;
 
 				pr_stdout("%s -> inode_ptr=%d\n", recs[k].fname, recs[k].inode_no);
@@ -1619,7 +2143,7 @@ int fs_la(void *d)
 		read_block(dir.blocks[i], (void *) &recs);
 
 		for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-			if (!recs[k].inode_no)
+			if (!recs[k].fname[0])
 				continue;
 
 			struct fs_inode f_inode;
@@ -1654,7 +2178,7 @@ int fs_la(void *d)
 			read_block(ext.blocks[i], (void *) &recs);
 
 			for (int k = 0; k < DIRECTORY_RECORDS_PER_BLOCK; k++) {
-				if (!recs[k].inode_no)
+				if (!recs[k].fname[0])
 					continue;
 
 				struct fs_inode f_inode;
@@ -1681,16 +2205,10 @@ int fs_stat(void *d)
 {
 	char *fname = *((char **) d);
 
-	int file_inode_ptr;
-	{
-		int *r = find_filename_in_directory(fs_cwd_inode_ptr, fname);
-		if (r == NULL) {
-			pr_err("no such file: '%s'\n", fname);
-			return 0;
-		}
-
-		file_inode_ptr = r[2];
-		free(r);
+	int file_inode_ptr = find_fname_in_directory(fs_cwd_inode_ptr, fname);
+	if (file_inode_ptr < 0) {
+		pr_err("no such file: '%s'\n", fname);
+		return 0;
 	}
 
 	struct fs_inode f;
@@ -1744,6 +2262,7 @@ int fs_use(void *d)
 	}
 
 	if (write_permitted) {
+		memset(fs_cwd, 0, sizeof(fs_cwd));
 		char *root_dir_path = "/";
 		fs_chdir((void *) &root_dir_path);
 
@@ -1874,10 +2393,15 @@ finish_current_block:
 	// inode0 -> root_dir_block
 	write_inode_ptr(0, free_block_index);
 
+	memset(fs_cwd, 0, sizeof(fs_cwd));
 	char *root_dir_path = "/";
 	fs_chdir((void *) &root_dir_path);
 
 	fs_cwd_inode_ptr = 0;
 
+	// add . and ..
+	fs_add_fname_to_directory(0, 0, ".");
+	fs_add_fname_to_directory(0, 0, "..");
+
 	return 0;
 }