Make libcephfs return error when unmounted?

[Noah Watkins]

Hi all,

A simple program like this:

int main(int argc, char **argv)
{
        int ret;
        struct ceph_mount_info *cmount;

        ceph_create(&cmount, NULL);
        //ceph_mount(cmount, NULL);
        ceph_chdir(cmount, "/");
}

will segfault because in the below snippet, cmount->get_client() returns NULL 
when ceph_mount(..) has not been been called with success.

extern "C" int ceph_chdir (struct ceph_mount_info *cmount, const char *s)       
                                                                      
{                                                                               
                                                                      
        return cmount->get_client()->chdir(s);                                  
                                                                           
}

It would be very useful to get a uniform error return value rather than the 
fault. Something like this came to mind:

diff --git a/src/libcephfs.cc b/src/libcephfs.cc
index b1481e6..4751e8f 100644
--- a/src/libcephfs.cc
+++ b/src/libcephfs.cc
@@ -180,6 +180,10 @@ public:
     return cct;
   }
 
+  bool is_mounted(void) {
+    return mounted;
+  }
+
 private:
   uint64_t msgr_nonce;
   bool mounted;
@@ -282,6 +286,8 @@ extern "C" const char* ceph_getcwd(struct ceph_mount_info 
*cmount)
 
 extern "C" int ceph_chdir (struct ceph_mount_info *cmount, const char *s)
 {
+  if (!cmount->is_mounted())
+    return -1004;
   return cmount->get_client()->chdir(s);
 }

Any thoughts on a good way to handle this?

-Noah--
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