[RFC] mount can figure out fstype automatically

Hi,

One of the pet peeves I have with FreeBSD is that
if I have a device with a local filesystem that I want to mount,
I need to explicitly know what type of filesystem is on the
device in order to mount it from the command-line.

For example,

mount -t cd9660
mount -t udf
mount -t ext2fs
mount -t msdosfs

Where this is particularly annoying is if I have multiple
USB thumb drives with different filesystems on them.

What I usually end up doing is something like:
file - < /dev/ad0s4

to figure out the filesystem type, and then mount -t [whatever] to mount it.

What I would like to do is:

mount /dev/ad0s4 /mnt

and if I do not specify a filesystem type with -t, the mount
program should "magically" figure out how to mount the disk.
This is closer to how the mount program behaves on Linux for example.

I've come up with a patch that does this, by interpreting
an fstype of "" as:
 - starting with "ufs", iterate over all the local filesystem types
   that we know about, and try to mount the device

Comments?



Index: sys/kern/vfs_mount.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/vfs_mount.c,v
retrieving revision 1.228
diff -u -u -r1.228 vfs_mount.c
--- sys/kern/vfs_mount.c	27 Jun 2006 14:46:31 -0000	1.228
+++ sys/kern/vfs_mount.c	8 Jul 2006 14:01:52 -0000
_at__at_ -567,6 +567,34 _at__at_
 }
 
 static int
+vfs_domount_try(struct thread *td, char *fspath, int fsflags,
+                 void *fsdata)
+{
+	struct vfsconf *vfsp;
+	int error;
+	printf("Mounting: %s first\n", "ufs");
+	error = vfs_domount(td, "ufs", fspath, fsflags, fsdata);
+	if (error == 0) {
+		printf("successfully mounted: %s\n", "ufs");
+	}
+	if (error != 0) {
+		TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
+			if ((strcmp("ufs", vfsp->vfc_name) != 0) &&
+			    !(vfsp->vfc_flags & VFCF_NETWORK) &&
+			    !(vfsp->vfc_flags & VFCF_SYNTHETIC)) {
+				printf("Mounting: %s\n", vfsp->vfc_name);
+				error = vfs_domount(td, vfsp->vfc_name, fspath, fsflags, fsdata);
+				if (error == 0) {
+					printf("successfully mounted: %s\n", vfsp->vfc_name);
+					break;
+				}
+			}
+		}
+	}
+        return error;
+}
+
+static int
 vfs_donmount(struct thread *td, int fsflags, struct uio *fsoptions)
 {
 	struct vfsoptlist *optlist;
_at__at_ -596,7 +624,7 _at__at_
 	 */
 	fstypelen = 0;
 	error = vfs_getopt(optlist, "fstype", (void **)&fstype, &fstypelen);
-	if (error || fstype[fstypelen - 1] != '\0') {
+	if (error || (fstypelen > 0 && fstype[fstypelen - 1] != '\0')) {
 		error = EINVAL;
 		if (errmsg != NULL)
 			strncpy(errmsg, "Invalid fstype", errmsg_len);
_at__at_ -606,6 +634,7 _at__at_
 	error = vfs_getopt(optlist, "fspath", (void **)&fspath, &fspathlen);
 	if (error || fspath[fspathlen - 1] != '\0') {
 		error = EINVAL;
+			printf("%s:%d EINVAL\n", __FILE__, __LINE__);
 		if (errmsg != NULL)
 			strncpy(errmsg, "Invalid fspath", errmsg_len);
 		goto bail;
_at__at_ -686,7 +715,14 _at__at_
 	}
 
 	mtx_lock(&Giant);
-	error = vfs_domount(td, fstype, fspath, fsflags, optlist);
+        if (fstypelen >  1) {
+		/* fstype was specified, go directly to vfs_domount() */
+                error = vfs_domount(td, fstype, fspath, fsflags, optlist);
+	}
+        else {
+		/* we do not know the fstype, try to probe for it */
+                error = vfs_domount_try(td, fspath, fsflags, optlist);
+	}
 	mtx_unlock(&Giant);
 bail:
 	/* copyout the errmsg */
Index: sbin/mount/mount.c
===================================================================
RCS file: /home/ncvs/src/sbin/mount/mount.c,v
retrieving revision 1.87
diff -u -u -r1.87 mount.c
--- sbin/mount/mount.c	10 Jun 2006 01:44:57 -0000	1.87
+++ sbin/mount/mount.c	8 Jul 2006 14:14:47 -0000
_at__at_ -200,7 +200,7 _at__at_
 
 	all = init_flags = 0;
 	vfslist = NULL;
-	vfstype = "ufs";
+	vfstype = "";
 	while ((ch = getopt(argc, argv, "adF:fo:prwt:uv")) != -1)
 		switch (ch) {
 		case 'a':
Index: sbin/mount/mount_fs.c
===================================================================
RCS file: /home/ncvs/src/sbin/mount/mount_fs.c,v
retrieving revision 1.2
diff -u -u -r1.2 mount_fs.c
--- sbin/mount/mount_fs.c	13 Nov 2005 01:27:57 -0000	1.2
+++ sbin/mount/mount_fs.c	8 Jul 2006 14:14:47 -0000
_at__at_ -50,6 +50,7 _at__at_
 
 #include <sys/param.h>
 #include <sys/mount.h>
+#include <sys/uio.h>
 
 #include <err.h>
 #include <getopt.h>
_at__at_ -82,8 +83,9 _at__at_
 	int iovlen;
 	int mntflags = 0;
 	int ch;
-	char *dev, *dir, mntpath[MAXPATHLEN];
+	char *dev, *dir, mntpath[MAXPATHLEN], frompath[MAXPATHLEN];
 	char fstype[32];
+	//char errmsg[1024] = { 0 };
 	char *p, *val;
 	int ret;
 
_at__at_ -121,15 +123,35 _at__at_
 	dir = argv[1];
 
 	(void)checkpath(dir, mntpath);
+	if (realpath(dev, frompath) != NULL) {
+		dev = frompath;
+	}
 	(void)rmslashes(dev, dev);
 
 	build_iovec(&iov, &iovlen, "fstype", fstype, (size_t)-1);
 	build_iovec(&iov, &iovlen, "fspath", mntpath, (size_t)-1);
 	build_iovec(&iov, &iovlen, "from", dev, (size_t)-1);
-	
+	//build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg));
+	printf("fstype: %s, fspath: %s, from: %s\n", fstype, mntpath, dev);
+retry:
 	ret = nmount(iov, iovlen, mntflags);
-	if (ret < 0)
-		err(1, "%s", dev);
+	if (ret < 0 && iov[1].iov_len == 0) {
+		/*
+		 * If an fstype was not specified, and nmount() failed,
+		 * try again with an fstype of "ufs".  This is for backwards
+		 * compatibility with older kernels which do not support
+		 * do_mount_try() with an fstype of "".
+		 */
+		iov[1].iov_base = strdup("ufs");
+		iov[1].iov_len = 4;
+		printf("Trying again....\n");
+		goto retry;
+	}
+
+	if (ret < 0) {
+		//err(1, "%s %s", dev, errmsg);
+		//err(1, "%s", dev);
+	}
 
 	return (ret);
 }


-- 
Craig Rodrigues        
rodrigc_at_crodrigues.org