Avoid double unmount on normal unmount in auto_unmount mode.

If a fuse filesystem was mounted in auto_unmount mode on top of an
already mounted filesystem, we would end up doing a double-unmount
when the fuse filesystem was unmounted properly.

Make the auto_unmount code less eager: unmount only if the mounted
filesystem has proper type and is returning 'Transport endpoint not
connected'.

diff --git a/ChangeLog.rst b/ChangeLog.rst
index 0b6ce98a3d28390d46bdb6770c9a0d6c7e85b9e9..73b90d7dd2007d4da605741912a105adb893ec07 100644 (file)
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -1,6 +1,9 @@
 Unreleased Changes
 =================
 
+* The `auto_unmount` mode now works correctly in combination with
+  autofs.
+
 * The FUSE_CAP_READDIRPLUS_AUTO capability is no longer enabled by
   default unless the file system defines both a readdir() and a
   readdirplus() handler.

diff --git a/util/fusermount.c b/util/fusermount.c
index 7a6ac01dd306d27277d6ac2b659dbd08cbab983a..8eb0fdcb40dd9a60d3307cea5d3edbbd80dc1070 100644 (file)
--- a/util/fusermount.c
+++ b/util/fusermount.c
@@ -237,6 +237,7 @@ static int check_is_mount_child(void *p)
        const char **a = p;
        const char *last = a[0];
        const char *mnt = a[1];
+       const char *type = a[2];
        int res;
        const char *procmounts = "/proc/mounts";
        int found;
@@ -284,7 +285,8 @@ static int check_is_mount_child(void *p)
                        continue;
                }
                if (entp->mnt_dir[0] == '/' &&
-                   strcmp(entp->mnt_dir + 1, last) == 0) {
+                   strcmp(entp->mnt_dir + 1, last) == 0 &&
+                   (!type || strcmp(entp->mnt_type, type) == 0)) {
                        found = 1;
                        break;
                }
@@ -317,11 +319,11 @@ static pid_t clone_newns(void *a)
 #endif
 }
 
-static int check_is_mount(const char *last, const char *mnt)
+static int check_is_mount(const char *last, const char *mnt, const char *type)
 {
        pid_t pid, p;
        int status;
-       const char *a[2] = { last, mnt };
+       const char *a[3] = { last, mnt, type };
 
        pid = clone_newns((void *) a);
        if (pid == (pid_t) -1) {
@@ -433,7 +435,7 @@ static int unmount_fuse_locked(const char *mnt, int quiet, int lazy)
        if (umount_nofollow_support()) {
                umount_flags |= UMOUNT_NOFOLLOW;
        } else {
-               res = check_is_mount(last, mnt);
+               res = check_is_mount(last, mnt, NULL);
                if (res == -1)
                        goto out;
        }
@@ -739,7 +741,7 @@ static int mount_notrunc(const char *source, const char *target,
 }
 
 
-static int do_mount(const char *mnt, char **typep, mode_t rootmode,
+static int do_mount(const char *mnt, const char **typep, mode_t rootmode,
                    int fd, const char *opts, const char *dev, char **sourcep,
                    char **mnt_optsp)
 {
@@ -1091,13 +1093,12 @@ static int open_fuse_device(char **devp)
 }
 
 
-static int mount_fuse(const char *mnt, const char *opts)
+static int mount_fuse(const char *mnt, const char *opts, const char **type)
 {
        int res;
        int fd;
        char *dev;
        struct stat stbuf;
-       char *type = NULL;
        char *source = NULL;
        char *mnt_opts = NULL;
        const char *real_mnt = mnt;
@@ -1121,7 +1122,7 @@ static int mount_fuse(const char *mnt, const char *opts)
        res = check_perm(&real_mnt, &stbuf, &mountpoint_fd);
        restore_privs();
        if (res != -1)
-               res = do_mount(real_mnt, &type, stbuf.st_mode & S_IFMT,
+               res = do_mount(real_mnt, type, stbuf.st_mode & S_IFMT,
                               fd, opts, dev, &source, &mnt_opts);
 
        if (mountpoint_fd != -1)
@@ -1137,7 +1138,7 @@ static int mount_fuse(const char *mnt, const char *opts)
        }
 
        if (geteuid() == 0) {
-               res = add_mount(source, mnt, type, mnt_opts);
+               res = add_mount(source, mnt, *type, mnt_opts);
                if (res == -1) {
                        /* Can't clean up mount in a non-racy way */
                        goto fail_close_fd;
@@ -1146,7 +1147,6 @@ static int mount_fuse(const char *mnt, const char *opts)
 
 out_free:
        free(source);
-       free(type);
        free(mnt_opts);
        free(dev);
 
@@ -1194,6 +1194,51 @@ static int send_fd(int sock_fd, int fd)
        return 0;
 }
 
+/* The parent fuse process has died: decide whether to auto_unmount.
+ *
+ * In the normal case (umount or fusermount -u), the filesystem
+ * has already been unmounted. If we simply unmount again we can
+ * cause problems with stacked mounts (e.g. autofs).
+ *
+ * So we unmount here only in abnormal case where fuse process has
+ * died without unmount happening. To detect this, we first look in
+ * the mount table to make sure the mountpoint is still mounted and
+ * has proper type. If so, we then see if opening the mount dir is
+ * returning 'Transport endpoint is not connected'.
+ *
+ * The order of these is important, because if autofs is in use,
+ * opening the dir to check for ENOTCONN will cause a new mount
+ * in the normal case where filesystem has been unmounted cleanly.
+ */
+static int should_auto_unmount(const char *mnt, const char *type)
+{
+       char *copy;
+       const char *last;
+       int result = 0;
+       int fd;
+
+       copy = strdup(mnt);
+       if (copy == NULL) {
+       fprintf(stderr, "%s: failed to allocate memory\n", progname);
+               return 0;
+       }
+
+       if (chdir_to_parent(copy, &last) == -1)
+               goto out;
+       if (check_is_mount(last, mnt, type) == -1)
+               goto out;
+
+       fd = open(mnt, O_RDONLY);
+       if (fd != -1) {
+               close(fd);
+       } else {
+               result = errno == ENOTCONN;
+       }
+out:
+       free(copy);
+       return result;
+}
+
 static void usage(void)
 {
        printf("%s: [options] mountpoint\n"
@@ -1228,6 +1273,7 @@ int main(int argc, char *argv[])
        char *commfd;
        int cfd;
        const char *opts = "";
+       const char *type = NULL;
 
        static const struct option long_opts[] = {
                {"unmount", no_argument, NULL, 'u'},
@@ -1315,7 +1361,7 @@ int main(int argc, char *argv[])
                goto err_out;
        }
 
-       fd = mount_fuse(mnt, opts);
+       fd = mount_fuse(mnt, opts, &type);
        if (fd == -1)
                goto err_out;
 
@@ -1360,6 +1406,10 @@ int main(int argc, char *argv[])
                }
        }
 
+       if (!should_auto_unmount(mnt, type)) {
+               goto success_out;
+       }
+
 do_unmount:
        if (geteuid() == 0)
                res = unmount_fuse(mnt, quiet, lazy);
@@ -1372,6 +1422,8 @@ do_unmount:
        }
        if (res == -1)
                goto err_out;
+
+success_out:
        free(mnt);
        return 0;