Fix a bug in file truncation. (#58)

src/core/fileobj.c

@@ -405,7 +405,10 @@ fileobj_getsize(fileobj_t *fobj)
 int
 fileobj_setsize(fileobj_t *fobj, size_t len)
 {
-	if (fileobj_dataload(fobj) == -1) {
+	/*
+	 * Only load the data if truncating to non-zero.
+	 */
+	if (len && fileobj_dataload(fobj) == -1) {
 		app_elog(LOG_DEBUG, "%s: fileobj_dataload() failed", __func__);
 		errno = EIO;
 		return -1;
@@ -415,7 +418,7 @@ fileobj_setsize(fileobj_t *fobj, size_t len)
 	 * Note: if new length is zero, then sbuffer_move() will free the
 	 * old buffer and will return NULL.
 	 */
-	if (len && sbuffer_move(&fobj->sbuf, len, 0) == NULL) {
+	if (sbuffer_move(&fobj->sbuf, len, 0) == NULL && len) {
 		app_elog(LOG_DEBUG, "%s: sbuffer_move() failed", __func__);
 		return -1;
 	}

src/core/storage.c

@@ -208,6 +208,7 @@ storage_map_obj(rvault_t *vault, int fd, size_t file_len)
 		return NULL;
 	}
 	if ((hdr = safe_mmap(file_len, fd, 0)) == NULL) {
+		app_elog(LOG_DEBUG, "%s: mmap() failed", __func__);
 		return NULL;
 	}
 	aetag_len = crypto_get_aetaglen(vault->crypto);
@@ -325,8 +326,10 @@ storage_read_data(rvault_t *vault, int fd, size_t file_len, sbuffer_t *sbuf)
 	if (FILEOBJ_EDATA_LEN(hdr) == 0) {
 		/*
 		 * Note: it is currently an error to have no encrypted data.
-		 * Empty file is represented as an empty file.
+		 * Empty file is represented as a fully empty file without
+		 * the header.
 		 */
+		app_elog(LOG_DEBUG, "%s: edata length is zero", __func__);
 		goto out;
 	}
 	memset(&tmpsbuf, 0, sizeof(sbuffer_t));

src/fuse/rvaultfs.c

@@ -100,7 +100,13 @@ rvaultfs_truncate(const char *path, off_t size)
 	if (size < 0) {
 		return -EINVAL;
 	}
-	if ((fobj = fileobj_open(vault, path, O_WRONLY, FOBJ_OMASK)) == NULL) {
+
+	/*
+	 * Note: use O_RDWR instead of O_WRONLY, since the data might have
+	 * to be loaded before truncation (e.g. in order decompress and
+	 * determine the correct offset).
+	 */
+	if ((fobj = fileobj_open(vault, path, O_RDWR, FOBJ_OMASK)) == NULL) {
 		return -errno;
 	}
 	if (fileobj_setsize(fobj, (size_t)size) == -1) {

src/tests/t_fileobj.c

@@ -23,6 +23,23 @@
 #define	TEST_BLOCK_COUNT	128
 #define	TEST_BLOCK_SIZE		(32U * 1024) // 32 KB
 
+static void
+test_file_basic(rvault_t *vault)
+{
+	fileobj_t *fobj;
+	ssize_t nbytes;
+
+	fobj = fileobj_open(vault, "/basic", O_CREAT | O_RDWR, FOBJ_OMASK);
+	assert(fobj != NULL);
+	fileobj_close(fobj);
+
+	fobj = fileobj_open(vault, "/basic", O_RDONLY, FOBJ_OMASK);
+	assert(fobj != NULL);
+	nbytes = fileobj_getsize(fobj);
+	assert(nbytes == 0);
+	fileobj_close(fobj);
+}
+
 static void
 test_file_expand(rvault_t *vault)
 {
@@ -118,7 +135,7 @@ test_file_onebyte(rvault_t *vault)
 }
 
 static void
-test_file_zero(rvault_t *vault)
+test_file_setsize(rvault_t *vault)
 {
 	static const unsigned zeros[16];
 	unsigned buf[16];
@@ -150,16 +167,34 @@ test_file_zero(rvault_t *vault)
 	nbytes = fileobj_pread(fobj, buf, sizeof(buf), 0);
 	assert(nbytes == 0);
 	fileobj_close(fobj);
+
+	/*
+	 * Write some data, shrink size, expand, check.
+	 */
+	fobj = fileobj_open(vault, "/empty", O_CREAT | O_RDWR, FOBJ_OMASK);
+	assert(fobj != NULL);
+
+	nbytes = fileobj_pwrite(fobj, (const void *)"ab", 2, 0);
+	assert(nbytes == 2);
+
+	fileobj_setsize(fobj, 1);
+	fileobj_setsize(fobj, 3);
+
+	nbytes = fileobj_pread(fobj, buf, sizeof(buf), 0);
+	assert(nbytes == 3);
+	assert(memcmp(buf, "a\0\0", 3) == 0);
+	fileobj_close(fobj);
 }
 
 static void
 run_tests(const char *cipher)
 {
 	char *base_path = NULL;
 	rvault_t *vault = mock_get_vault(cipher, &base_path);
+	test_file_basic(vault);
 	test_file_expand(vault);
 	test_file_onebyte(vault);
-	test_file_zero(vault);
+	test_file_setsize(vault);
 	mock_cleanup_vault(vault, base_path);
 }