From 9b08492bc733f3b1b1eefc87a4c52d9673432e42 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@gmail.com>
Date: Sun, 24 Mar 2019 21:07:45 -0400
Subject: [PATCH] check if fs is mounted before running fsck

---
 cmd_device.c |  4 ++--
 cmd_fsck.c   |  5 +++++
 tools-util.c | 28 +++++++++++++---------------
 tools-util.h |  4 +++-
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/cmd_device.c b/cmd_device.c
index 797b958c..92d3125b 100644
--- a/cmd_device.c
+++ b/cmd_device.c
@@ -385,14 +385,14 @@ int cmd_device_resize(int argc, char *argv[])
 
 	struct stat dev_stat = xfstat(dev_fd);
 
-	char *mount = dev_to_mount(dev);
+	struct mntent *mount = dev_to_mount(dev);
 	if (mount) {
 		if (!S_ISBLK(dev_stat.st_mode))
 			die("%s is mounted but isn't a block device?!", dev);
 
 		printf("Doing online resize of %s\n", dev);
 
-		struct bchfs_handle fs = bcache_fs_open(mount);
+		struct bchfs_handle fs = bcache_fs_open(mount->mnt_dir);
 
 		unsigned idx = bchu_disk_get_idx(fs, dev_stat.st_rdev);
 
diff --git a/cmd_fsck.c b/cmd_fsck.c
index 617cf252..e0961b99 100644
--- a/cmd_fsck.c
+++ b/cmd_fsck.c
@@ -23,6 +23,7 @@ static void usage(void)
 int cmd_fsck(int argc, char *argv[])
 {
 	struct bch_opts opts = bch2_opts_empty();
+	unsigned i;
 	int opt, ret = 0;
 
 	opt_set(opts, degraded, true);
@@ -56,6 +57,10 @@ int cmd_fsck(int argc, char *argv[])
 	if (!argc)
 		die("Please supply device(s) to check");
 
+	for (i = 0; i < argc; i++)
+		if (dev_mounted_rw(argv[i]))
+			die("%s is mounted read-write - aborting", argv[i]);
+
 	struct bch_fs *c = bch2_fs_open(argv, argc, opts);
 	if (IS_ERR(c))
 		die("error opening %s: %s", argv[0], strerror(-PTR_ERR(c)));
diff --git a/tools-util.c b/tools-util.c
index 486bbacf..e4d2beae 100644
--- a/tools-util.c
+++ b/tools-util.c
@@ -610,26 +610,18 @@ char *dev_to_path(dev_t dev)
 	return path;
 }
 
-char *dev_to_mount(char *dev)
+struct mntent *dev_to_mount(char *dev)
 {
-	char *line = NULL, *ret = NULL;
-	size_t n = 0;
-
-	FILE *f = fopen("/proc/mounts", "r");
+	struct mntent *mnt, *ret = NULL;
+	FILE *f = setmntent("/proc/mounts", "r");
 	if (!f)
 		die("error opening /proc/mounts: %m");
 
 	struct stat d1 = xstat(dev);
 
-	while (getline(&line, &n, f) != -1) {
-		char *d, *p = line;
-		char *devs = strsep(&p, " ");
-		char *mount = strsep(&p, " ");
+	while ((mnt = getmntent(f))) {
+		char *d, *p = mnt->mnt_fsname;
 
-		if (!devs || !mount)
-			continue;
-
-		p = devs;
 		while ((d = strsep(&p, ":"))) {
 			struct stat d2;
 
@@ -648,12 +640,18 @@ char *dev_to_mount(char *dev)
 					continue;
 			}
 
-			ret = strdup(mount);
+			ret = mnt;
 			goto found;
 		}
 	}
 found:
 	fclose(f);
-	free(line);
 	return ret;
 }
+
+bool dev_mounted_rw(char *dev)
+{
+	struct mntent *mnt = dev_to_mount(dev);
+
+	return mnt && !hasmntopt(mnt, "ro");
+}
diff --git a/tools-util.h b/tools-util.h
index ae63f723..e5c35084 100644
--- a/tools-util.h
+++ b/tools-util.h
@@ -2,6 +2,7 @@
 #define _TOOLS_UTIL_H
 
 #include <errno.h>
+#include <mntent.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -153,7 +154,8 @@ u32 crc32c(u32, const void *, size_t);
 
 char *dev_to_name(dev_t);
 char *dev_to_path(dev_t);
-char *dev_to_mount(char *);
+struct mntent *dev_to_mount(char *);
+bool dev_mounted_rw(char *);
 
 #define args_shift(_nr)							\
 do {									\