Btrfs devel - Mar 2008 - [PATCH] check if partition is mounted before mkfs

This saves from the blunder of formatting a live mounted filesystem.
This can be extended to get the mount flags of the filesystem
mounted.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@gmail.com>
--- 

 mkfs.c  |    8 +++++++-
 utils.c |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 utils.h |    1 +
 3 files changed, 60 insertions(+), 1 deletion(-)

diff -r 13295e4517d1 mkfs.c
--- a/mkfs.c	Tue Mar 04 13:07:22 2008 -0500
+++ b/mkfs.c	Thu Mar 20 12:15:27 2008 +0530
@@ -173,7 +173,7 @@ int main(int ac, char **av)
 	u64 block_count = 0;
 	int fd;
 	struct stat st;
-	int ret;
+	int ret, mounted = 0;
 	int i;
 	u32 leafsize = 16 * 1024;
 	u32 sectorsize = 4096;
@@ -232,6 +232,12 @@ int main(int ac, char **av)
 		fprintf(stderr, "unable to stat %s\n", file);
 		exit(1);
 	}
+	if (check_mounted(file, &mounted)==0)
+		if (mounted) {
+			fprintf(stderr, "%s is mounted\n", file);
+			exit(1);
+		}
+
 	if (block_count == 0) {
 		block_count = device_size(fd, &st);
 		if (block_count == 0) {
diff -r 13295e4517d1 utils.c
--- a/utils.c	Tue Mar 04 13:07:22 2008 -0500
+++ b/utils.c	Thu Mar 20 12:15:27 2008 +0530
@@ -25,6 +25,7 @@
 #include <uuid/uuid.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <mntent.h>
 #include "kerncompat.h"
 #include "radix-tree.h"
 #include "ctree.h"
@@ -230,3 +231,54 @@ error:
 error:
 	return ret;
 }
+
+
+int check_mounted(char *file, int *flag)
+{
+	struct mntent   *mnt;
+	struct stat     st_buf;
+	dev_t           file_dev=0, file_rdev=0;
+	ino_t           file_ino=0;
+	FILE            *f;
+
+	*flag = 0;
+	if ((f = setmntent ("/proc/mounts", "r")) == NULL)
+		return errno;
+
+	if (stat(file, &st_buf) < 0) {
+		return errno;
+	}
+	else {
+		if (S_ISBLK(st_buf.st_mode)) {
+			file_rdev = st_buf.st_rdev;
+		} else {
+			file_dev = st_buf.st_dev;
+			file_ino = st_buf.st_ino;
+		}
+	}
+
+
+	while ((mnt = getmntent (f)) != NULL) {
+		if (strcmp(file, mnt->mnt_fsname) == 0)
+			break;
+		if (stat(mnt->mnt_fsname, &st_buf) == 0) {
+			if (S_ISBLK(st_buf.st_mode)) {
+				if (file_rdev && (file_rdev == st_buf.st_rdev))
+					break;
+			} else {
+				if (file_dev && ((file_dev == st_buf.st_dev) &&
+							(file_ino == st_buf.st_ino)))
+					break;
+			}
+		}
+	}
+
+	if (mnt) {
+		/* found an entry in mnt table */
+		*flag = 1;
+	}
+
+	endmntent (f);
+	return 0;
+}
+
diff -r 13295e4517d1 utils.h
--- a/utils.h	Tue Mar 04 13:07:22 2008 -0500
+++ b/utils.h	Thu Mar 20 12:15:27 2008 +0530
@@ -22,4 +22,5 @@ int make_btrfs(int fd, u64 new_blocks[4]
 		u32 leafsize, u32 sectorsize, u32 stripesize);
 int btrfs_make_root_dir(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root, u64 objectid);
+int check_mounted(char *devicename, int *mounted);
 #endif

On Thursday 20 March 2008, Goldwyn Rodrigues wrote:
> This saves from the blunder of formatting a live mounted filesystem.
> This can be extended to get the mount flags of the filesystem
> mounted.
Thanks, I'll merge this in.

-chris