fuse: allow requests during mount (needed for SELinux labels)

Resurrecting Jeff's commit:

  commit 7d0397c2144810c8a396e00187a6617873c94002
  Author: Jeff Darcy <jdarcy@redhat.com>

      fuse: allow requests during mount (needed for SELinux labels)

that was reverted as of:

  commit 4ab1c326f3862714b960302f06c6323d6291b695
  Author: Vijay Bellur <vijay@gluster.com>

      Revert "fuse: allow requests during mount (needed for SELinux labels)"

BUG: 811217
Change-Id: Ia1af402897e6a7290acf79617c34fdc804751729
Signed-off-by: Csaba Henk <csaba@redhat.com>
Reviewed-on: http://review.gluster.com/3452
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vijay@gluster.com>

2 files changed, 51 insertions, 11 deletions

diff --git a/contrib/fuse-include/fuse-mount.h b/contrib/fuse-include/fuse-mount.h
index 9f83faf02a0..7a3756d92b8 100644
--- a/contrib/fuse-include/fuse-mount.h
+++ b/contrib/fuse-include/fuse-mount.h
@@ -9,4 +9,4 @@
 
 void gf_fuse_unmount (const char *mountpoint, int fd);
 int gf_fuse_mount (const char *mountpoint, char *fsname, char *mnt_param,
-                   pid_t *mtab_pid);
+                   pid_t *mtab_pid, int status_fd);
diff --git a/contrib/fuse-lib/mount.c b/contrib/fuse-lib/mount.c
index 800fd193e6c..8c5da3d619f 100644
--- a/contrib/fuse-lib/mount.c
+++ b/contrib/fuse-lib/mount.c
@@ -544,19 +544,25 @@ gf_fuse_unmount (const char *mountpoint, int fd)
 
 #ifndef FUSE_UTIL
 static int
-fuse_mount_sys (const char *mountpoint, char *fsname, char *mnt_param, pid_t *mtab_pid)
+fuse_mount_sys (const char *mountpoint, char *fsname, char *mnt_param, pid_t *mtab_pid, int in_fd, int status_fd)
 {
         int fd = -1, ret = -1;
         unsigned mounted = 0;
         char *mnt_param_mnt = NULL;
         char *fstype = "fuse.glusterfs";
         char *source = fsname;
+        pid_t mypid = -1;
 
-        fd = open ("/dev/fuse", O_RDWR);
-        if (fd == -1) {
-                GFFUSE_LOGERR ("cannot open /dev/fuse (%s)", strerror (errno));
-
-                return -1;
+        if (in_fd >= 0) {
+                fd = in_fd;
+        }
+        else {
+                fd = open ("/dev/fuse", O_RDWR);
+                if (fd == -1) {
+                        GFFUSE_LOGERR ("cannot open /dev/fuse (%s)",
+                                        strerror (errno));
+                        return -1;
+                }
         }
 
         ret = asprintf (&mnt_param_mnt,
@@ -567,8 +573,14 @@ fuse_mount_sys (const char *mountpoint, char *fsname, char *mnt_param, pid_t *mt
 
                 goto out;
         }
+        ret = fork();
+        if (ret != 0) {
+                goto parent_out;
+        }
+        GFFUSE_LOGERR("calling mount");
         ret = mount (source, mountpoint, fstype, 0,
                      mnt_param_mnt);
+        GFFUSE_LOGERR("mount returned %d",ret);
         if (ret == -1 && errno == ENODEV) {
                 /* fs subtype support was added by 79c0b2df aka
                    v2.6.21-3159-g79c0b2d. Probably we have an
@@ -607,11 +619,31 @@ fuse_mount_sys (const char *mountpoint, char *fsname, char *mnt_param, pid_t *mt
                 }
         }
 
- out:
+        ret = 0;
+out:
+        if (status_fd >= 0) {
+                GFFUSE_LOGERR("writing status");
+                (void)write(status_fd,&ret,sizeof(ret));
+                mypid = getpid();
+                /*
+                 * This seems awkward, but the alternative would be to add
+                 * or change return values for functions in multiple layers,
+                 * just so they can store the value for later retrieval by
+                 * the code already running in the right context at the other
+                 * end of this pipe.  That's a lot of disruption for nothing.
+                 */
+                (void)write(status_fd,&mypid,sizeof(mypid));
+        }
+        GFFUSE_LOGERR("Mount child exiting");
+        exit(0);
+
+parent_out:
         if (ret == -1) {
                 if (mounted)
                         umount2 (mountpoint, 2); /* lazy umount */
-                close (fd);
+                if (fd != in_fd) {
+                        close (fd);
+                }
                 fd = -1;
         }
         FREE (mnt_param_mnt);
@@ -651,13 +683,21 @@ escape (char *s)
 
 int
 gf_fuse_mount (const char *mountpoint, char *fsname, char *mnt_param,
-               pid_t *mtab_pid)
+               pid_t *mtab_pid, int status_fd)
 {
         int fd = -1, rv = -1;
         char *fm_mnt_params = NULL, *p = NULL;
         char *efsname = NULL;
 
-        fd = fuse_mount_sys (mountpoint, fsname, mnt_param, mtab_pid);
+        fd = open ("/dev/fuse", O_RDWR);
+        if (fd == -1) {
+                GFFUSE_LOGERR ("cannot open /dev/fuse (%s)",
+                                strerror (errno));
+                return -1;
+        }
+
+        fd = fuse_mount_sys (mountpoint, fsname, mnt_param, mtab_pid, fd,
+                             status_fd);
         if (fd == -1) {
                 gf_log ("glusterfs-fuse", GF_LOG_INFO,
                         "direct mount failed (%s), "