Re: [PATCH] e4defrag: Add option -m mtab to e4defrag

[Eric Sandeen <sandeen@redhat.com>]

On 10/17/12 11:52 AM, Ashish Sangwan wrote:
> Currently, e4defrag will not work on machines where /etc/mtab is not present
> OR is empty.
> This patch does 3 things:
> a) Add option "-m mtab" to e4defrag so that user can specify any file to
> be scanned for otbtaining mounted filesystems info.

Under what conditions would this be useful; i.e. when is mtab information
ever in a file other than /etc/mtab?

Thanks,
-Eric

> b) If mtab option is not specified, first we try to scan /proc/mounts, if failed
> to access this file, we try with /etc/mtab.
> c) In function is_ext4, check if the varibale "mnt_type" is null before
> calling strcmp, otherwise segfault would occur if mtab is empty. 
> 
> Signed-off-by: Ashish Sangwan <ashish.sangwan2@gmail.com>
> Signed-off-by: Namjae Jeon <linkinjeon@gmail.com>
> ---
>  misc/e4defrag.8.in |   10 ++++++++++
>  misc/e4defrag.c    |   34 ++++++++++++++++++++++------------
>  2 files changed, 32 insertions(+), 12 deletions(-)
> 
> diff --git a/misc/e4defrag.8.in b/misc/e4defrag.8.in
> index 75e1bc9..7090e51 100644
> --- a/misc/e4defrag.8.in
> +++ b/misc/e4defrag.8.in
> @@ -9,6 +9,9 @@ e4defrag \- online defragmenter for ext4 filesystem
>  [
>  .B \-v
>  ]
> +[
> +.B \-m mtab
> +]
>  .I target
>  \&...
>  .SH DESCRIPTION
> @@ -57,6 +60,13 @@ is never defragmented.
>  .B \-v
>  Print error messages and the fragmentation count before and after defrag for
>  each file.
> +.TP
> +.B \-m mtab
> +This option will specify the file to be scanned for obtaining mounted filesystems
> +information. If this option is not specified, the default is to use
> +.B /proc/mounts .
> +If this file is not accessible, e4defrag will try to get required information from
> +.B /etc/mtab
>  .SH NOTES
>  .B e4defrag
>  does not support swap file, files in lost+found directory, and files allocated
> diff --git a/misc/e4defrag.c b/misc/e4defrag.c
> index 4b31d03..3567e9f 100644
> --- a/misc/e4defrag.c
> +++ b/misc/e4defrag.c
> @@ -123,6 +123,7 @@
>  #define NGMSG_FILE_OPEN		"Failed to open"
>  #define NGMSG_FILE_UNREG	"File is not regular file"
>  #define NGMSG_LOST_FOUND	"Can not process \"lost+found\""
> +#define _PATH_PROC_MOUNTS       "/proc/mounts"
>  
>  /* Data type for filesystem-wide blocks number */
>  typedef unsigned long long ext4_fsblk_t;
> @@ -262,10 +263,8 @@ static int fallocate64(int fd, int mode, loff_t offset, loff_t len)
>   * @dir_path_len:	the length of directory.
>   */
>  static int get_mount_point(const char *devname, char *mount_point,
> -							int dir_path_len)
> +			   int dir_path_len, const char *mtab)
>  {
> -	/* Refer to /etc/mtab */
> -	const char	*mtab = MOUNTED;
>  	FILE		*fp = NULL;
>  	struct mntent	*mnt = NULL;
>  	struct stat64	sb;
> @@ -278,7 +277,7 @@ static int get_mount_point(const char *devname, char *mount_point,
>  
>  	fp = setmntent(mtab, "r");
>  	if (fp == NULL) {
> -		perror("Couldn't access /etc/mtab");
> +		printf("Couldn't access %s\n", mtab);
>  		return -1;
>  	}
>  
> @@ -313,14 +312,12 @@ static int get_mount_point(const char *devname, char *mount_point,
>   *
>   * @file:		the file's name.
>   */
> -static int is_ext4(const char *file, char *devname)
> +static int is_ext4(const char *file, char *devname, const char *mtab)
>  {
>  	int 	maxlen = 0;
>  	int	len, ret;
>  	FILE	*fp = NULL;
>  	char	*mnt_type = NULL;
> -	/* Refer to /etc/mtab */
> -	const char	*mtab = MOUNTED;
>  	char	file_path[PATH_MAX + 1];
>  	struct mntent	*mnt = NULL;
>  	struct statfs64	fsbuf;
> @@ -345,7 +342,7 @@ static int is_ext4(const char *file, char *devname)
>  
>  	fp = setmntent(mtab, "r");
>  	if (fp == NULL) {
> -		perror("Couldn't access /etc/mtab");
> +		printf("Couldn't access %s", mtab);
>  		return -1;
>  	}
>  
> @@ -374,6 +371,10 @@ static int is_ext4(const char *file, char *devname)
>  	}
>  
>  	endmntent(fp);
> +	if (mnt_type == NULL) {
> +		printf("Could not get mount information from %s\n", mtab);
> +		return -1;
> +	}
>  	if (strcmp(mnt_type, FS_EXT4) == 0) {
>  		FREE(mnt_type);
>  		return 0;
> @@ -1724,6 +1725,7 @@ int main(int argc, char *argv[])
>  	int	success_flag = 0;
>  	char	dir_name[PATH_MAX + 1];
>  	char	dev_name[PATH_MAX + 1];
> +	char *mtab = NULL;
>  	struct stat64	buf;
>  	ext2_filsys fs = NULL;
>  
> @@ -1731,7 +1733,7 @@ int main(int argc, char *argv[])
>  	if (argc == 1)
>  		goto out;
>  
> -	while ((opt = getopt(argc, argv, "vc")) != EOF) {
> +	while ((opt = getopt(argc, argv, "vcm:")) != EOF) {
>  		switch (opt) {
>  		case 'v':
>  			mode_flag |= DETAIL;
> @@ -1739,11 +1741,19 @@ int main(int argc, char *argv[])
>  		case 'c':
>  			mode_flag |= STATISTIC;
>  			break;
> +		case 'm':
> +			mtab = optarg;
> +			break;
>  		default:
>  			goto out;
>  		}
>  	}
> -
> +	if (!mtab) {
> +		if (access(_PATH_PROC_MOUNTS, R_OK) == 0)
> +			mtab = _PATH_PROC_MOUNTS;
> +		else
> +			mtab = _PATH_MOUNTED;
> +	} 
>  	if (argc == optind)
>  		goto out;
>  
> @@ -1797,7 +1807,7 @@ int main(int argc, char *argv[])
>  		if (S_ISBLK(buf.st_mode)) {
>  			/* Block device */
>  			strncpy(dev_name, argv[i], strnlen(argv[i], PATH_MAX));
> -			if (get_mount_point(argv[i], dir_name, PATH_MAX) < 0)
> +			if (get_mount_point(argv[i], dir_name, PATH_MAX, mtab) < 0)
>  				continue;
>  			if (lstat64(dir_name, &buf) < 0) {
>  				perror(NGMSG_FILE_INFO);
> @@ -1833,7 +1843,7 @@ int main(int argc, char *argv[])
>  		 * filesystem type checked in get_mount_point()
>  		 */
>  		if (arg_type == FILENAME || arg_type == DIRNAME) {
> -			if (is_ext4(argv[i], dev_name) < 0)
> +			if (is_ext4(argv[i], dev_name, mtab) < 0)
>  				continue;
>  			if (realpath(argv[i], dir_name) == NULL) {
>  				perror("Couldn't get full path");
>