btrfs-progs: add error handling for device_get_partition_size()

The function device_get_partition_size() has all kinds of error paths,
but it has no way to return error other than returning 0.

This is not helpful for end users to know what's going wrong.

Change that function to return int for error code, and a dedicated u64
pointer to return the device size in bytes.

All existing call sites will exit early using that error code.
The only exception is load_device_info() which will only give a warning
and continue.

Signed-off-by: Qu Wenruo <[email protected]>

Author: adam900710

cmds/filesystem-usage.c

@@ -820,8 +820,14 @@ static int load_device_info(int fd, struct array *devinfos)
 			strcpy(info->path, "missing");
 		} else {
 			strcpy(info->path, (char *)dev_info.path);
-			info->device_size =
-				device_get_partition_size((const char *)dev_info.path);
+			ret = device_get_partition_size((const char *)dev_info.path,
+							&info->device_size);
+			if (ret < 0) {
+				errno = -ret;
+				warning("failed to get device size for %s: %m",
+					dev_info.path);
+				info->device_size = 0;
+			}
 		}
 		info->size = dev_info.total_bytes;
 		ndevs++;

cmds/replace.c

@@ -269,7 +269,12 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 		strncpy_null((char *)start_args.start.srcdev_name, srcdev,
 			     BTRFS_DEVICE_PATH_NAME_MAX + 1);
 		start_args.start.srcdevid = 0;
-		srcdev_size = device_get_partition_size(srcdev);
+		ret = device_get_partition_size(srcdev, &srcdev_size);
+		if (ret < 0) {
+			errno = -ret;
+			error("failed to get device size for %s: %m", srcdev);
+			goto leave_with_error;
+		}
 	} else {
 		error("source device must be a block device or a devid");
 		goto leave_with_error;
@@ -279,7 +284,12 @@ static int cmd_replace_start(const struct cmd_struct *cmd,
 	if (ret)
 		goto leave_with_error;
 
-	dstdev_size = device_get_partition_size(dstdev);
+	ret = device_get_partition_size(dstdev, &dstdev_size);
+	if (ret < 0) {
+		errno = -ret;
+		error("failed to get device size for %s: %m", dstdev);
+		goto leave_with_error;
+	}
 	if (srcdev_size > dstdev_size) {
 		error("target device smaller than source device (required %llu bytes)",
 			srcdev_size);

common/device-utils.c

@@ -323,7 +323,7 @@ u64 device_get_partition_size_fd_stat(int fd, const struct stat *st)
 	return 0;
 }
 
-static u64 device_get_partition_size_sysfs(const char *dev)
+static int device_get_partition_size_sysfs(const char *dev, u64 *size_ret)
 {
 	int ret;
 	char path[PATH_MAX] = {};
@@ -335,47 +335,45 @@ static u64 device_get_partition_size_sysfs(const char *dev)
 
 	name = realpath(dev, path);
 	if (!name)
-		return 0;
+		return -errno;
 	name = path_basename(path);
 
 	ret = path_cat3_out(sysfs, "/sys/class/block", name, "size");
 	if (ret < 0)
-		return 0;
+		return ret;
 	sysfd = open(sysfs, O_RDONLY);
 	if (sysfd < 0)
-		return 0;
+		return -errno;
 	ret = sysfs_read_file(sysfd, sizebuf, sizeof(sizebuf));
-	if (ret < 0) {
-		close(sysfd);
-		return 0;
-	}
+	close(sysfd);
+	if (ret < 0)
+		return ret;
 	errno = 0;
 	size = strtoull(sizebuf, NULL, 10);
-	if (size == ULLONG_MAX && errno == ERANGE) {
-		close(sysfd);
-		return 0;
-	}
-	close(sysfd);
-
-	/* <device>/size value is in sector (512B) unit. */
-	return size << SECTOR_SHIFT;
+	if (size == ULLONG_MAX && errno == ERANGE)
+		return -ERANGE;
+	/* Extra overflow check. */
+	if (size > ULLONG_MAX >> SECTOR_SHIFT)
+		return -ERANGE;
+	*size_ret = size << SECTOR_SHIFT;
+	return 0;
 }
 
-u64 device_get_partition_size(const char *dev)
+int device_get_partition_size(const char *dev, u64 *size_ret)
 {
 	u64 result;
 	int fd = open(dev, O_RDONLY);
 
 	if (fd < 0)
-		return device_get_partition_size_sysfs(dev);
+		return device_get_partition_size_sysfs(dev, size_ret);
 
 	if (ioctl(fd, BLKGETSIZE64, &result) < 0) {
 		close(fd);
-		return 0;
+		return -errno;
 	}
 	close(fd);
-
-	return result;
+	*size_ret = result;
+	return 0;
 }
 
 /*

common/device-utils.h

@@ -42,7 +42,7 @@ enum {
  */
 int device_discard_blocks(int fd, u64 start, u64 len);
 int device_zero_blocks(int fd, off_t start, size_t len, const bool direct);
-u64 device_get_partition_size(const char *dev);
+int device_get_partition_size(const char *dev, u64 *size_ret);
 u64 device_get_partition_size_fd_stat(int fd, const struct stat *st);
 int device_get_queue_param(const char *file, const char *param, char *buf, size_t len);
 u64 device_get_zone_unusable(int fd, u64 flags);