[PATCH v2] erofs-utils: get block device size correctly

[Gao Xiang]

Hi shenmeng,

On Wed, Aug 07, 2019 at 10:36:55PM +0800, shenmeng999 at 126.com wrote:
> From: shenmeng996 <shenmeng999 at 126.com>
> 
> fstat return block device's size of zero.
> use ioctl to get block device's size.
> 
> Signed-off-by: shenmeng996 <shenmeng999 at 126.com>


Thanks for your patch v2 :)

It looks good to me, and I update this patch so that
autoconf can check these new header files.
https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git/commit/?h=experimental&id=0f225449962b4a9716985e7530a395a9500d0de6
Do you agree with this modification? please share your thought about this.

Thanks,
Gao Xiang

diff --git a/configure.ac b/configure.ac
index 6f4eacc..fcdf30a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -73,12 +73,14 @@ AC_CHECK_HEADERS(m4_flatten([
 	fcntl.h
 	inttypes.h
 	linux/falloc.h
+	linux/fs.h
 	linux/types.h
 	limits.h
 	stddef.h
 	stdint.h
 	stdlib.h
 	string.h
+	sys/ioctl.h
 	sys/stat.h
 	sys/time.h
 	unistd.h
diff --git a/lib/io.c b/lib/io.c
index 93328d3..15c5a35 100644
--- a/lib/io.c
+++ b/lib/io.c
@@ -9,7 +9,11 @@
 #define _LARGEFILE64_SOURCE
 #define _GNU_SOURCE
 #include <sys/stat.h>
+#include <sys/ioctl.h>
 #include "erofs/io.h"
+#ifdef HAVE_LINUX_FS_H
+#include <linux/fs.h>
+#endif
 #ifdef HAVE_LINUX_FALLOC_H
 #include <linux/falloc.h>
 #endif
@@ -21,6 +25,26 @@ static const char *erofs_devname;
 static int erofs_devfd = -1;
 static u64 erofs_devsz;
 
+int dev_get_blkdev_size(int fd, u64 *bytes)
+{
+	errno = ENOTSUP;
+#ifdef BLKGETSIZE64
+	if (ioctl(fd, BLKGETSIZE64, bytes) >= 0)
+		return 0;
+#endif
+
+#ifdef BLKGETSIZE
+	{
+		unsigned long size;
+		if (ioctl(fd, BLKGETSIZE, &size) >= 0) {
+			*bytes = ((u64)size << 9);
+			return 0;
+		}
+	}
+#endif
+	return -errno;
+}
+
 void dev_close(void)
 {
 	close(erofs_devfd);
@@ -49,7 +73,12 @@ int dev_open(const char *dev)
 
 	switch (st.st_mode & S_IFMT) {
 	case S_IFBLK:
-		erofs_devsz = st.st_size;
+		ret = dev_get_blkdev_size(fd, &erofs_devsz);
+		if (ret) {
+			erofs_err("failed to get block device size(%s).", dev);
+			close(fd);
+			return ret;
+		}
 		break;
 	case S_IFREG:
 		ret = ftruncate(fd, 0);
-- 
2.17.1