2 files changed, 35 insertions, 27 deletions

diff --git a/util-linux/Config.in b/util-linux/Config.in
index 76e9ff97f..fbcf62476 100644
--- a/util-linux/Config.in
+++ b/util-linux/Config.in
@@ -393,6 +393,13 @@ config CONFIG_UMOUNT
           the tool to use.  If you enabled the 'mount' utility, you almost certainly
           also want to enable 'umount'.
 
+config CONFIG_FEATURE_UMOUNT_ALL
+        bool "  umount -a option"
+        default n
+        depends on CONFIG_UMOUNT
+        help
+          Support -a option to unmount all currently mounted filesystems.
+
 comment "Common options for mount/umount"
         depends on CONFIG_MOUNT || CONFIG_UMOUNT
 
diff --git a/util-linux/umount.c b/util-linux/umount.c
index 14ff41588..8c0558466 100644
--- a/util-linux/umount.c
+++ b/util-linux/umount.c
@@ -21,15 +21,14 @@
 #include <getopt.h>
 #include "busybox.h"
 
-#define OPTION_STRING           "flaDnrv"
+#define OPTION_STRING           "flDnrva"
 #define OPT_FORCE                       1
 #define OPT_LAZY                        2
-#define OPT_ALL                         4
-#define OPT_DONTFREELOOP                8
-#define OPT_NO_MTAB                     16
-#define OPT_REMOUNT                     32
-/* -v is ignored */
-
+#define OPT_DONTFREELOOP        4
+#define OPT_NO_MTAB                     8
+#define OPT_REMOUNT                     16
+#define OPT_IGNORED                     32      // -v is ignored
+#define OPT_ALL                         (ENABLE_FEATURE_UMOUNT_ALL ? 64 : 0)
 
 extern int umount_main(int argc, char **argv)
 {
@@ -61,24 +60,25 @@ extern int umount_main(int argc, char **argv)
          * umounts the most recent entries first. */
 
         m=mtl=0;
-        if(!(fp = setmntent(bb_path_mtab_file, "r")))
-                bb_error_msg_and_die("Cannot open %s", bb_path_mtab_file);
-        while (getmntent_r(fp,&me,path,sizeof(path))) {
-                m=xmalloc(sizeof(struct mtab_list));
-                m->next=mtl;
-                m->device=bb_xstrdup(me.mnt_fsname);
-                m->dir=bb_xstrdup(me.mnt_dir);
-                mtl=m;
-        }
-        endmntent(fp);
-
-        /* If we're umounting all, then m points to the start of the list and
-         * the argument list should be empty (which will match all). */
-        if(!(opt & OPT_ALL)) {
-                m=0;
-                if(argc <= 0) bb_show_usage();
-        }
+        if(opt & OPT_ALL) {
+
+                /* If we're umounting all, then m points to the start of the list and
+                 * the argument list should be empty (which will match all). */
+
+                if(!(fp = setmntent(bb_path_mtab_file, "r")))
+                        bb_error_msg_and_die("Cannot open %s", bb_path_mtab_file);
+                while (getmntent_r(fp,&me,path,sizeof(path))) {
+                        m=xmalloc(sizeof(struct mtab_list));
+                        m->next=mtl;
+                        m->device=bb_xstrdup(me.mnt_fsname);
+                        m->dir=bb_xstrdup(me.mnt_dir);
+                        mtl=m;
+                }
+                endmntent(fp);
 
+        /* If we're not mounting all, we need at least one argument. */
+        } else if(argc <= 0) bb_show_usage();
+        
         // Loop through everything we're supposed to umount, and do so.
         for(;;) {
                 int curstat;
@@ -92,9 +92,10 @@ extern int umount_main(int argc, char **argv)
                 else {
                         // Get next command line argument (and look it up in mtab list)
                         realpath(*argv++, path);
-                        for(m = mtl; m; m = m->next)
-                                if(!strcmp(path, m->dir) || !strcmp(path, m->device))
-                                        break;
+                        if (ENABLE_FEATURE_MTAB_SUPPORT)
+                                for(m = mtl; m; m = m->next)
+                                        if(!strcmp(path, m->dir) || !strcmp(path, m->device))
+                                                break;
                 }
 
                 // Let's ask the thing nicely to unmount.