Get path size with stat or ioctl

If we're making a file system in a real device then we need to get
the device size with an ioctl.

utils/src/dev.c

@@ -0,0 +1,42 @@
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+#include <errno.h>
+
+#include "sparse.h"
+#include "dev.h"
+
+int device_size(char *path, int fd, u64 *size)
+{
+        struct stat st;
+        int ret;
+
+        if (fstat(fd, &st)) {
+                ret = -errno;
+                fprintf(stderr, "failed to stat '%s': %s (%d)\n",
+                        path, strerror(errno), errno);
+                return ret;
+        }
+
+        if (S_ISREG(st.st_mode)) {
+                *size = st.st_size;
+        } else if (S_ISBLK(st.st_mode)) {
+                if (ioctl(fd, BLKGETSIZE64, size)) {
+                        ret = -errno;
+                        fprintf(stderr, "BLKGETSIZE64 failed '%s': %s (%d)\n",
+                                path, strerror(errno), errno);
+                        return ret;
+                }
+        } else {
+                fprintf(stderr, "path isn't regular or device file '%s'\n",
+                        path);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+

utils/src/dev.h

@@ -0,0 +1,6 @@
+#ifndef _DEV_H_
+#define _DEV_H_
+
+int device_size(char *path, int fd, u64 *size);
+
+#endif

utils/src/mkfs.c

@@ -16,6 +16,7 @@
 #include "format.h"
 #include "crc.h"
 #include "rand.h"
+#include "dev.h"
 
 /*
  * Update the block's header and write it out.
@@ -52,8 +53,8 @@ static int write_new_fs(char *path, int fd)
 	struct scoutfs_key root_key;
 	struct timeval tv;
 	char uuid_str[37];
-	struct stat st;
 	unsigned int i;
+	u64 size;
 	u64 total_chunks;
 	u64 blkno;
 	void *buf;
@@ -73,14 +74,14 @@ static int write_new_fs(char *path, int fd)
 		goto out;
 	}
 
-	if (fstat(fd, &st)) {
-		ret = -errno;
+	ret = device_size(path, fd, &size);
+	if (ret) {
 		fprintf(stderr, "failed to stat '%s': %s (%d)\n",
 			path, strerror(errno), errno);
 		goto out;
 	}
 
-	total_chunks = st.st_size >> SCOUTFS_CHUNK_SHIFT;
+	total_chunks = size >> SCOUTFS_CHUNK_SHIFT;
 
 	root_key.inode = cpu_to_le64(SCOUTFS_ROOT_INO);
 	root_key.type = SCOUTFS_INODE_KEY;