Use virFileOperation hook function in virStorageBackendFileSystemVolBuild

There were a few operations on the storage volume file that were still
being done as root, which will fail if the file is on a root-squashed
NFS share. The result was that attempts to create a storage volume of
type "raw" on a root-squashed NFS share would fail.

This patch uses the newly introduced "hook" function in
virFileOperation to execute all those file operations in the child
process that's run under the uid that owns the file (and, presumably,
has permission to write to the NFS share)

* src/storage/storage_backend.c: use virFileOperation() in
  virStorageBackendCreateRaw, turning virStorageBackendCreateRaw()
  into a new createRawFileOpHook() hook

src/storage/storage_backend.c

@@ -270,61 +270,33 @@ cleanup:
     return ret;
 }
 
-int
-virStorageBackendCreateRaw(virConnectPtr conn ATTRIBUTE_UNUSED,
-                           virStoragePoolObjPtr pool,
-                           virStorageVolDefPtr vol,
-                           virStorageVolDefPtr inputvol,
-                           unsigned int flags ATTRIBUTE_UNUSED)
-{
-    int fd = -1;
-    int ret = -1;
-    int createstat;
-    unsigned long long remain;
-    char *buf = NULL;
-
-    if (vol->target.encryption != NULL) {
-        virStorageReportError(VIR_ERR_NO_SUPPORT,
-                              "%s", _("storage pool does not support encrypted "
-                                      "volumes"));
-        return -1;
-    }
-
-    if ((createstat = virFileOperation(vol->target.path, O_RDWR | O_CREAT | O_EXCL,
-                                       vol->target.perms.mode,
-                                       vol->target.perms.uid, vol->target.perms.gid,
-                                       NULL, NULL,
-                                       VIR_FILE_OP_FORCE_PERMS |
-                                       (pool->def->type == VIR_STORAGE_POOL_NETFS
-                                        ? VIR_FILE_OP_AS_UID : 0))) < 0) {
-        virReportSystemError(createstat,
-                             _("cannot create path '%s'"),
-                             vol->target.path);
-        goto cleanup;
-    }
+struct createRawFileOpHookData {
+    virStorageVolDefPtr vol;
+    virStorageVolDefPtr inputvol;
+};
 
-    if ((fd = open(vol->target.path, O_RDWR | O_EXCL | O_DSYNC)) < 0) {
-        virReportSystemError(errno,
-                             _("cannot open new path '%s'"),
-                             vol->target.path);
-        goto cleanup;
-    }
+static int createRawFileOpHook(int fd, void *data) {
+    struct createRawFileOpHookData *hdata = data;
+    int ret = 0;
+    unsigned long long remain;
 
     /* Seek to the final size, so the capacity is available upfront
      * for progress reporting */
-    if (ftruncate(fd, vol->capacity) < 0) {
+    if (ftruncate(fd, hdata->vol->capacity) < 0) {
+        ret = errno;
         virReportSystemError(errno,
                              _("cannot extend file '%s'"),
-                             vol->target.path);
+                             hdata->vol->target.path);
         goto cleanup;
     }
 
-    remain = vol->allocation;
+    remain = hdata->vol->allocation;
 
-    if (inputvol) {
-        int res = virStorageBackendCopyToFD(vol, inputvol,
+    if (hdata->inputvol) {
+        int res = virStorageBackendCopyToFD(hdata->vol, hdata->inputvol,
                                             fd, &remain, 1);
         if (res < 0)
+            ret = -res;
             goto cleanup;
     }
 
@@ -341,11 +313,11 @@ virStorageBackendCreateRaw(virConnectPtr conn ATTRIBUTE_UNUSED,
 
                 if (bytes > remain)
                     bytes = remain;
-                if ((r = safezero(fd, 0, vol->allocation - remain,
+                if ((r = safezero(fd, 0, hdata->vol->allocation - remain,
                                   bytes)) != 0) {
-                    virReportSystemError(r,
-                                         _("cannot fill file '%s'"),
-                                         vol->target.path);
+                    ret = errno;
+                    virReportSystemError(r, _("cannot fill file '%s'"),
+                                         hdata->vol->target.path);
                     goto cleanup;
                 }
                 remain -= bytes;
@@ -354,28 +326,51 @@ virStorageBackendCreateRaw(virConnectPtr conn ATTRIBUTE_UNUSED,
             int r;
 
             if ((r = safezero(fd, 0, 0, remain)) != 0) {
-                virReportSystemError(r,
-                                     _("cannot fill file '%s'"),
-                                     vol->target.path);
+                ret = errno;
+                virReportSystemError(r, _("cannot fill file '%s'"),
+                                     hdata->vol->target.path);
                 goto cleanup;
             }
         }
     }
 
-    if (close(fd) < 0) {
-        virReportSystemError(errno,
-                             _("cannot close file '%s'"),
+cleanup:
+    return ret;
+}
+
+int
+virStorageBackendCreateRaw(virConnectPtr conn ATTRIBUTE_UNUSED,
+                           virStoragePoolObjPtr pool,
+                           virStorageVolDefPtr vol,
+                           virStorageVolDefPtr inputvol,
+                           unsigned int flags ATTRIBUTE_UNUSED)
+{
+    int ret = -1;
+    int createstat;
+    struct createRawFileOpHookData hdata = { vol, inputvol };
+
+    if (vol->target.encryption != NULL) {
+        virStorageReportError(VIR_ERR_NO_SUPPORT,
+                              "%s", _("storage pool does not support encrypted "
+                                      "volumes"));
+        goto cleanup;
+    }
+
+    if ((createstat = virFileOperation(vol->target.path, O_RDWR | O_CREAT | O_EXCL,
+                                       vol->target.perms.mode,
+                                       vol->target.perms.uid, vol->target.perms.gid,
+                                       createRawFileOpHook, &hdata,
+                                       VIR_FILE_OP_FORCE_PERMS |
+                                       (pool->def->type == VIR_STORAGE_POOL_NETFS
+                                        ? VIR_FILE_OP_AS_UID : 0))) < 0) {
+    virReportSystemError(createstat,
+                         _("cannot create path '%s'"),
                          vol->target.path);
     goto cleanup;
     }
-    fd = -1;
 
     ret = 0;
 cleanup:
-    if (fd != -1)
-        close(fd);
-    VIR_FREE(buf);
-
     return ret;
 }