mount: use the mount syscall directly

Allow zfs datasets to be mounted on Linux without relying on the
invocation of an external processes.  This is the same behavior
which is implemented for FreeBSD.

Use of the libmount library was originally considered because it 
provides functionality to properly lock and update the /etc/mtab 
file.  However, these days /etc/mtab is typically a symlink to 
/proc/self/mounts so there's nothing to updated.  Therefore, we
call mount(2) directly and avoid any additional dependencies. 

If required the legacy behavior can be enabled by setting the 
ZFS_MOUNT_HELPER environment variable.  This may be needed in
environments where SELinux in enabled and the zfs binary does  
not have mount permission.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Felix Dörre <[email protected]>
#10294 

1 files changed, 2 insertions, 234 deletions

diff --git a/cmd/mount_zfs/mount_zfs.c b/cmd/mount_zfs/mount_zfs.c
index a37dd6f53..87d2ccadc 100644
--- a/cmd/mount_zfs/mount_zfs.c
+++ b/cmd/mount_zfs/mount_zfs.c
@@ -42,185 +42,6 @@
 
 libzfs_handle_t *g_zfs;
 
-typedef struct option_map {
-	const char *name;
-	unsigned long mntmask;
-	unsigned long zfsmask;
-} option_map_t;
-
-static const option_map_t option_map[] = {
-	/* Canonicalized filesystem independent options from mount(8) */
-	{ MNTOPT_NOAUTO,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_DEFAULTS,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_NODEVICES,	MS_NODEV,	ZS_COMMENT	},
-	{ MNTOPT_DIRSYNC,	MS_DIRSYNC,	ZS_COMMENT	},
-	{ MNTOPT_NOEXEC,	MS_NOEXEC,	ZS_COMMENT	},
-	{ MNTOPT_GROUP,		MS_GROUP,	ZS_COMMENT	},
-	{ MNTOPT_NETDEV,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_NOFAIL,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_NOSUID,	MS_NOSUID,	ZS_COMMENT	},
-	{ MNTOPT_OWNER,		MS_OWNER,	ZS_COMMENT	},
-	{ MNTOPT_REMOUNT,	MS_REMOUNT,	ZS_COMMENT	},
-	{ MNTOPT_RO,		MS_RDONLY,	ZS_COMMENT	},
-	{ MNTOPT_RW,		MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_SYNC,		MS_SYNCHRONOUS,	ZS_COMMENT	},
-	{ MNTOPT_USER,		MS_USERS,	ZS_COMMENT	},
-	{ MNTOPT_USERS,		MS_USERS,	ZS_COMMENT	},
-	/* acl flags passed with util-linux-2.24 mount command */
-	{ MNTOPT_ACL,		MS_POSIXACL,	ZS_COMMENT	},
-	{ MNTOPT_NOACL,		MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_POSIXACL,	MS_POSIXACL,	ZS_COMMENT	},
-#ifdef MS_NOATIME
-	{ MNTOPT_NOATIME,	MS_NOATIME,	ZS_COMMENT	},
-#endif
-#ifdef MS_NODIRATIME
-	{ MNTOPT_NODIRATIME,	MS_NODIRATIME,	ZS_COMMENT	},
-#endif
-#ifdef MS_RELATIME
-	{ MNTOPT_RELATIME,	MS_RELATIME,	ZS_COMMENT	},
-#endif
-#ifdef MS_STRICTATIME
-	{ MNTOPT_STRICTATIME,	MS_STRICTATIME,	ZS_COMMENT	},
-#endif
-#ifdef MS_LAZYTIME
-	{ MNTOPT_LAZYTIME,	MS_LAZYTIME,	ZS_COMMENT	},
-#endif
-	{ MNTOPT_CONTEXT,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_FSCONTEXT,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_DEFCONTEXT,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_ROOTCONTEXT,	MS_COMMENT,	ZS_COMMENT	},
-#ifdef MS_I_VERSION
-	{ MNTOPT_IVERSION,	MS_I_VERSION,	ZS_COMMENT	},
-#endif
-#ifdef MS_MANDLOCK
-	{ MNTOPT_NBMAND,	MS_MANDLOCK,	ZS_COMMENT	},
-#endif
-	/* Valid options not found in mount(8) */
-	{ MNTOPT_BIND,		MS_BIND,	ZS_COMMENT	},
-#ifdef MS_REC
-	{ MNTOPT_RBIND,		MS_BIND|MS_REC,	ZS_COMMENT	},
-#endif
-	{ MNTOPT_COMMENT,	MS_COMMENT,	ZS_COMMENT	},
-#ifdef MS_NOSUB
-	{ MNTOPT_NOSUB,		MS_NOSUB,	ZS_COMMENT	},
-#endif
-#ifdef MS_SILENT
-	{ MNTOPT_QUIET,		MS_SILENT,	ZS_COMMENT	},
-#endif
-	/* Custom zfs options */
-	{ MNTOPT_XATTR,		MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_NOXATTR,	MS_COMMENT,	ZS_COMMENT	},
-	{ MNTOPT_ZFSUTIL,	MS_COMMENT,	ZS_ZFSUTIL	},
-	{ NULL,			0,		0		} };
-
-/*
- * Break the mount option in to a name/value pair.  The name is
- * validated against the option map and mount flags set accordingly.
- */
-static int
-parse_option(char *mntopt, unsigned long *mntflags,
-    unsigned long *zfsflags, int sloppy)
-{
-	const option_map_t *opt;
-	char *ptr, *name, *value = NULL;
-	int error = 0;
-
-	name = strdup(mntopt);
-	if (name == NULL)
-		return (ENOMEM);
-
-	for (ptr = name; ptr && *ptr; ptr++) {
-		if (*ptr == '=') {
-			*ptr = '\0';
-			value = ptr+1;
-			VERIFY3P(value, !=, NULL);
-			break;
-		}
-	}
-
-	for (opt = option_map; opt->name != NULL; opt++) {
-		if (strncmp(name, opt->name, strlen(name)) == 0) {
-			*mntflags |= opt->mntmask;
-			*zfsflags |= opt->zfsmask;
-			error = 0;
-			goto out;
-		}
-	}
-
-	if (!sloppy)
-		error = ENOENT;
-out:
-	/* If required further process on the value may be done here */
-	free(name);
-	return (error);
-}
-
-/*
- * Translate the mount option string in to MS_* mount flags for the
- * kernel vfs.  When sloppy is non-zero unknown options will be ignored
- * otherwise they are considered fatal are copied in to badopt.
- */
-static int
-parse_options(char *mntopts, unsigned long *mntflags, unsigned long *zfsflags,
-    int sloppy, char *badopt, char *mtabopt)
-{
-	int error = 0, quote = 0, flag = 0, count = 0;
-	char *ptr, *opt, *opts;
-
-	opts = strdup(mntopts);
-	if (opts == NULL)
-		return (ENOMEM);
-
-	*mntflags = 0;
-	opt = NULL;
-
-	/*
-	 * Scan through all mount options which must be comma delimited.
-	 * We must be careful to notice regions which are double quoted
-	 * and skip commas in these regions.  Each option is then checked
-	 * to determine if it is a known option.
-	 */
-	for (ptr = opts; ptr && !flag; ptr++) {
-		if (opt == NULL)
-			opt = ptr;
-
-		if (*ptr == '"')
-			quote = !quote;
-
-		if (quote)
-			continue;
-
-		if (*ptr == '\0')
-			flag = 1;
-
-		if ((*ptr == ',') || (*ptr == '\0')) {
-			*ptr = '\0';
-
-			error = parse_option(opt, mntflags, zfsflags, sloppy);
-			if (error) {
-				strcpy(badopt, opt);
-				goto out;
-
-			}
-
-			if (!(*mntflags & MS_REMOUNT) &&
-			    !(*zfsflags & ZS_ZFSUTIL)) {
-				if (count > 0)
-					strlcat(mtabopt, ",", MNT_LINE_MAX);
-
-				strlcat(mtabopt, opt, MNT_LINE_MAX);
-				count++;
-			}
-
-			opt = NULL;
-		}
-	}
-
-out:
-	free(opts);
-	return (error);
-}
-
 /*
  * Return the pool/dataset to mount given the name passed to mount.  This
  * is expected to be of the form pool/dataset, however may also refer to
@@ -345,34 +166,6 @@ mtab_update(char *dataset, char *mntpoint, char *type, char *mntopts)
 	return (MOUNT_SUCCESS);
 }
 
-static void
-append_mntopt(const char *name, const char *val, char *mntopts,
-    char *mtabopt, boolean_t quote)
-{
-	char tmp[MNT_LINE_MAX];
-
-	snprintf(tmp, MNT_LINE_MAX, quote ? ",%s=\"%s\"" : ",%s=%s", name, val);
-
-	if (mntopts)
-		strlcat(mntopts, tmp, MNT_LINE_MAX);
-
-	if (mtabopt)
-		strlcat(mtabopt, tmp, MNT_LINE_MAX);
-}
-
-static void
-zfs_selinux_setcontext(zfs_handle_t *zhp, zfs_prop_t zpt, const char *name,
-    char *mntopts, char *mtabopt)
-{
-	char context[ZFS_MAXPROPLEN];
-
-	if (zfs_prop_get(zhp, zpt, context, sizeof (context),
-	    NULL, NULL, 0, B_FALSE) == 0) {
-		if (strcmp(context, "none") != 0)
-			append_mntopt(name, context, mntopts, mtabopt, B_TRUE);
-	}
-}
-
 int
 main(int argc, char **argv)
 {
@@ -449,7 +242,7 @@ main(int argc, char **argv)
 	}
 
 	/* validate mount options and set mntflags */
-	error = parse_options(mntopts, &mntflags, &zfsflags, sloppy,
+	error = zfs_parse_mount_options(mntopts, &mntflags, &zfsflags, sloppy,
 	    badopt, mtabopt);
 	if (error) {
 		switch (error) {
@@ -502,32 +295,7 @@ main(int argc, char **argv)
 		return (MOUNT_USAGE);
 	}
 
-	/*
-	 * Checks to see if the ZFS_PROP_SELINUX_CONTEXT exists
-	 * if it does, create a tmp variable in case it's needed
-	 * checks to see if the selinux context is set to the default
-	 * if it is, allow the setting of the other context properties
-	 * this is needed because the 'context' property overrides others
-	 * if it is not the default, set the 'context' property
-	 */
-	if (zfs_prop_get(zhp, ZFS_PROP_SELINUX_CONTEXT, prop, sizeof (prop),
-	    NULL, NULL, 0, B_FALSE) == 0) {
-		if (strcmp(prop, "none") == 0) {
-			zfs_selinux_setcontext(zhp, ZFS_PROP_SELINUX_FSCONTEXT,
-			    MNTOPT_FSCONTEXT, mntopts, mtabopt);
-			zfs_selinux_setcontext(zhp, ZFS_PROP_SELINUX_DEFCONTEXT,
-			    MNTOPT_DEFCONTEXT, mntopts, mtabopt);
-			zfs_selinux_setcontext(zhp,
-			    ZFS_PROP_SELINUX_ROOTCONTEXT, MNTOPT_ROOTCONTEXT,
-			    mntopts, mtabopt);
-		} else {
-			append_mntopt(MNTOPT_CONTEXT, prop,
-			    mntopts, mtabopt, B_TRUE);
-		}
-	}
-
-	/* A hint used to determine an auto-mounted snapshot mount point */
-	append_mntopt(MNTOPT_MNTPOINT, mntpoint, mntopts, NULL, B_FALSE);
+	zfs_adjust_mount_options(zhp, mntpoint, mntopts, mtabopt);
 
 	/* treat all snapshots as legacy mount points */
 	if (zfs_get_type(zhp) == ZFS_TYPE_SNAPSHOT)