virfile: Rework virFileIsSharedFixFUSE

There are couple of things wrong with the current implementation.
The first one is that in the first loop the code tries to build a
list of fuse.glusterfs mount points. Well, since the strings are
allocated in a temporary buffer and are not duplicated this
results in wrong decision made later in the code.

The second problem is that the code does not take into account
subtree mounts. For instance, if there's a fuse.gluster mounted
at /some/path and another FS mounted at /some/path/subdir the
code would not recognize this subdir mount.
Reported-by: NHan Han <hhan@redhat.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>

src/util/virfile.c

@@ -3468,18 +3468,14 @@ static int
 virFileIsSharedFixFUSE(const char *path,
                        long long *f_type)
 {
-    char *dirpath = NULL;
-    const char **mounts = NULL;
-    size_t nmounts = 0;
-    char *p;
     FILE *f = NULL;
     struct mntent mb;
     char mntbuf[1024];
+    char *mntDir = NULL;
+    char *mntType = NULL;
+    size_t maxMatching = 0;
     int ret = -1;
 
-    if (VIR_STRDUP(dirpath, path) < 0)
-        return -1;
-
     if (!(f = setmntent(PROC_MOUNTS, "r"))) {
         virReportSystemError(errno,
                              _("Unable to open %s"),
@@ -3488,43 +3484,36 @@ virFileIsSharedFixFUSE(const char *path,
     }
 
     while (getmntent_r(f, &mb, mntbuf, sizeof(mntbuf))) {
-        if (STRNEQ("fuse.glusterfs", mb.mnt_type))
-            continue;
+        const char *p;
+        size_t len = strlen(mb.mnt_dir);
 
-        if (VIR_APPEND_ELEMENT_COPY(mounts, nmounts, mb.mnt_dir) < 0)
-            goto cleanup;
-    }
+        if (!(p = STRSKIP(path, mb.mnt_dir)))
+            continue;
 
-    /* Add NULL sentinel so that this is a virStringList */
-    if (VIR_REALLOC_N(mounts, nmounts + 1) < 0)
-        goto cleanup;
-    mounts[nmounts] = NULL;
+        if (*(p - 1) != '/' && *p != '/' && *p != '\0')
+            continue;
 
-    do {
-        if ((p = strrchr(dirpath, '/')) == NULL) {
-            virReportSystemError(EINVAL,
-                                 _("Invalid relative path '%s'"), path);
-            goto cleanup;
+        if (len > maxMatching) {
+            maxMatching = len;
+            VIR_FREE(mntType);
+            VIR_FREE(mntDir);
+            if (VIR_STRDUP(mntDir, mb.mnt_dir) < 0 ||
+                VIR_STRDUP(mntType, mb.mnt_type) < 0)
+                goto cleanup;
         }
+    }
 
-        if (p == dirpath)
-            *(p+1) = '\0';
-        else
-            *p = '\0';
-
-        if (virStringListHasString(mounts, dirpath)) {
-            VIR_DEBUG("Found gluster FUSE mountpoint=%s for path=%s. "
-                      "Fixing shared FS type", dirpath, path);
-            *f_type = GFS2_MAGIC;
-            break;
-        }
-    } while (p != dirpath);
+    if (STREQ_NULLABLE(mntType, "fuse.glusterfs")) {
+        VIR_DEBUG("Found gluster FUSE mountpoint=%s for path=%s. "
+                  "Fixing shared FS type", mntDir, path);
+        *f_type = GFS2_MAGIC;
+    }
 
     ret = 0;
  cleanup:
+    VIR_FREE(mntType);
+    VIR_FREE(mntDir);
     endmntent(f);
-    VIR_FREE(mounts);
-    VIR_FREE(dirpath);
     return ret;
 }
 

tests/virfiledata/mounts3.txt

@@ -31,3 +31,5 @@ hugetlbfs /hugepages2M hugetlbfs rw,relatime,mode=1777,pagesize=2M 0 0
 none /run/user/1000 tmpfs rw,relatime,mode=700,uid=1000 0 0
 host:/nfs /nfs nfs4 rw,relatime,vers=4.1,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp6,timeo=600,retrans=2,sec=sys,clientaddr=::,local_lock=none,addr=:: 0 0
 dev /nfs/blah devtmpfs rw,nosuid,relatime,size=10240k,nr_inodes=4093060,mode=755 0 0
+host:/gv0 /gluster fuse.glusterfs rw 0 0
+root@host:/tmp/mkdir /gluster/sshfs fuse.sshfs rw 0 0

tests/virfiletest.c

@@ -454,6 +454,8 @@ mymain(void)
     DO_TEST_FILE_IS_SHARED_FS_TYPE("mounts2.txt", "/run/user/501/gvfs/some/file", false);
     DO_TEST_FILE_IS_SHARED_FS_TYPE("mounts3.txt", "/nfs/file", true);
     DO_TEST_FILE_IS_SHARED_FS_TYPE("mounts3.txt", "/nfs/blah", false);
+    DO_TEST_FILE_IS_SHARED_FS_TYPE("mounts3.txt", "/gluster/file", true);
+    DO_TEST_FILE_IS_SHARED_FS_TYPE("mounts3.txt", "/gluster/sshfs/file", false);
 
     return ret != 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 }