lib/blkdev: add open_blkdev_or_file() function

Purpose of this function is to open a path that is potentially pointing to a
block device or file without races.  The function also proper open(3) flags
are used to check the device is not busy, and finally warning is been
printed if a block device happens to be misaligned.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/blkdev.c b/lib/blkdev.c
index 5f495822e..a57b3672b 100644
--- a/lib/blkdev.c
+++ b/lib/blkdev.c
@@ -25,9 +25,15 @@
 # include <sys/disk.h>
 #endif
 
+#ifndef EBADFD
+# define EBADFD 77		/* File descriptor in bad state */
+#endif
+
 #include "blkdev.h"
 #include "c.h"
 #include "linux_version.h"
+#include "fileutils.h"
+#include "nls.h"
 
 static long
 blkdev_valid_offset (int fd, off_t offset) {
@@ -254,6 +260,24 @@ int blkdev_is_misaligned(int fd)
 #endif
 }
 
+int open_blkdev_or_file(const struct stat *st, const char *name, const int oflag)
+{
+	int fd;
+
+	if (S_ISBLK(st->st_mode)) {
+		fd = open(name, oflag | O_EXCL);
+	} else
+		fd = open(name, oflag);
+	if (-1 < fd && !is_same_inode(fd, st)) {
+		close(fd);
+		errno = EBADFD;
+		return -1;
+	}
+	if (-1 < fd && S_ISBLK(st->st_mode) && blkdev_is_misaligned(fd))
+		warnx(_("warning: %s is misaligned"), name);
+	return fd;
+}
+
 int blkdev_is_cdrom(int fd)
 {
 #ifdef CDROM_GET_CAPABILITY