linux-kernel - [PATCH] libf2fs: check more conditions on mounted filesystem

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Message-id: <1375430989-4689-1-git-send-email-jaegeuk.kim@samsung.com>
Date:	Fri, 02 Aug 2013 17:09:49 +0900
From:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Jaegeuk Kim <jaegeuk.kim@...sung.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: [PATCH] libf2fs: check more conditions on mounted filesystem

In the case of lazy umount, "umount -l", some processes are able to use the
file system even if its mountpoint was disconnected.
At this moment, we should not allow mkfs.f2fs.
This patch adds this condition check.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
---
 fsck/main.c        |  2 +-
 include/f2fs_fs.h  |  2 +-
 lib/libf2fs.c      | 60 +++++++++++++++++++++++++++++++++++++++---------------
 mkfs/f2fs_format.c |  2 +-
 4 files changed, 47 insertions(+), 19 deletions(-)

diff --git a/fsck/main.c b/fsck/main.c
index 80db15d..a0144fc 100644
--- a/fsck/main.c
+++ b/fsck/main.c
@@ -183,7 +183,7 @@ int main (int argc, char **argv)
 
 	f2fs_parse_options(argc, argv);
 
-	if (f2fs_dev_is_mounted(&config) < 0)
+	if (f2fs_dev_is_umounted(&config) < 0)
 		return -1;
 
 	/* Get device */
diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
index d0fc79e..7081e5e 100644
--- a/include/f2fs_fs.h
+++ b/include/f2fs_fs.h
@@ -641,7 +641,7 @@ extern u_int32_t f2fs_cal_crc32(u_int32_t, void *, int);
 extern int f2fs_crc_valid(u_int32_t blk_crc, void *buf, int len);
 
 extern void f2fs_init_configuration(struct f2fs_configuration *);
-extern int f2fs_dev_is_mounted(struct f2fs_configuration *);
+extern int f2fs_dev_is_umounted(struct f2fs_configuration *);
 extern int f2fs_get_device_info(struct f2fs_configuration *);
 
 extern int dev_read(void *, __u64, size_t);
diff --git a/lib/libf2fs.c b/lib/libf2fs.c
index b02072f..6947425 100644
--- a/lib/libf2fs.c
+++ b/lib/libf2fs.c
@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <mntent.h>
@@ -365,31 +366,58 @@ void f2fs_init_configuration(struct f2fs_configuration *c)
 	c->device_name = NULL;
 }
 
-int f2fs_dev_is_mounted(struct f2fs_configuration *c)
+static int is_mounted(const char *mpt, const char *device)
 {
 	FILE *file = NULL;
 	struct mntent *mnt = NULL;
 
-	file = setmntent(MOUNTED, "r");
-	if (file == NULL) {
-		/* if failed due to /etc/mtab file not present
-		   try with /proc/mounts */
-		file = setmntent("/proc/mounts", "r");
-		if (file == NULL)
-			return 0;
-	}
+	file = setmntent(mpt, "r");
+	if (file == NULL)
+		return 0;
 
-	while (1) {
-		mnt = getmntent(file);
-		if (mnt == NULL)
+	while ((mnt = getmntent(file)) != NULL) {
+		if (!strcmp(device, mnt->mnt_fsname))
 			break;
-		if (!strcmp(c->device_name, mnt->mnt_fsname)) {
-			endmntent(file);
-			MSG(0, "\tError: Not available on mounted device!\n");
+	}
+	endmntent(file);
+	return mnt ? 1 : 0;
+}
+
+int f2fs_dev_is_umounted(struct f2fs_configuration *c)
+{
+	struct stat st_buf;
+	int ret = 0;
+
+	ret = is_mounted(MOUNTED, c->device_name);
+	if (ret) {
+		MSG(0, "\tError: Not available on mounted device!\n");
+		return -1;
+	}
+
+	/*
+	 * if failed due to /etc/mtab file not present
+	 * try with /proc/mounts.
+	 */
+	ret = is_mounted("/proc/mounts", c->device_name);
+	if (ret) {
+		MSG(0, "\tError: Not available on mounted device!\n");
+		return -1;
+	}
+
+	/*
+	 * If f2fs is umounted with -l, the process can still use
+	 * the file system. In this case, we should not format.
+	 */
+	if (stat(c->device_name, &st_buf) == 0 && S_ISBLK(st_buf.st_mode)) {
+		int fd = open(c->device_name, O_RDONLY | O_EXCL);
+
+		if (fd >= 0) {
+			close(fd);
+		} else if (errno == EBUSY) {
+			MSG(0, "\tError: In use by the system!\n");
 			return -1;
 		}
 	}
-	endmntent(file);
 	return 0;
 }
 
diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
index d60f990..5b017c7 100644
--- a/mkfs/f2fs_format.c
+++ b/mkfs/f2fs_format.c
@@ -998,7 +998,7 @@ int main(int argc, char *argv[])
 
 	f2fs_parse_options(argc, argv);
 
-	if (f2fs_dev_is_mounted(&config) < 0)
+	if (f2fs_dev_is_umounted(&config) < 0)
 		return -1;
 
 	if (f2fs_get_device_info(&config) < 0)
-- 
1.8.3.1.437.g0dbd812

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