Fs exporter correctly handles hardlink

Fixed the fs exporter to handle the case where hardlink method
was requested but pulp and export locations are in different
partitions so can't share the same inode.
Explicitly checks if its on a diff share/partition
Also checks if FileExists for Symlinks to avoid FileExistsError

fixes #1949
fixes #3187

Co-authored-by: Grant Gainey <ggainey@users.noreply.github.com>
(cherry picked from commit b03d0ff)

Author: 2 people

CHANGES/1949.bugfix

@@ -0,0 +1 @@
+Fixed the fs exporter to handle the case where there are pre-existing files in the location that FileSystem attempts to export to you get a FileExistsError.

CHANGES/3187.bugfix

@@ -0,0 +1 @@
+Fixed the fs exporter to handle the case where hardlink method was requested but pulp and export locations are in different partitions so can't share the same inode.

pulpcore/app/tasks/export.py

@@ -2,6 +2,7 @@
 import json
 import logging
 import os
+import os.path
 import subprocess
 import tarfile
 
@@ -66,16 +67,27 @@ def _export_to_file_system(path, relative_paths_to_artifacts, method=FS_EXPORT_M
         and method != FS_EXPORT_METHODS.WRITE
     ):
         raise RuntimeError(_("Only write is supported for non-filesystem storage."))
+    os.makedirs(path)
+    export_not_on_same_filesystem = (
+        settings.DEFAULT_FILE_STORAGE == "pulpcore.app.models.storage.FileSystem"
+        and os.stat(settings.MEDIA_ROOT).st_dev != os.stat(path).st_dev
+    )
+
+    if method == FS_EXPORT_METHODS.HARDLINK and export_not_on_same_filesystem:
+        log.info(_("Hard link cannot be created, file will be copied."))
+        method = FS_EXPORT_METHODS.WRITE
 
     for relative_path, artifact in relative_paths_to_artifacts.items():
         dest = os.path.join(path, relative_path)
         os.makedirs(os.path.split(dest)[0], exist_ok=True)
 
         if method == FS_EXPORT_METHODS.SYMLINK:
             src = os.path.join(settings.MEDIA_ROOT, artifact.file.name)
+            os.path.lexists(dest) and os.unlink(dest)
             os.symlink(src, dest)
         elif method == FS_EXPORT_METHODS.HARDLINK:
             src = os.path.join(settings.MEDIA_ROOT, artifact.file.name)
+            os.path.lexists(dest) and os.unlink(dest)
             os.link(src, dest)
         elif method == FS_EXPORT_METHODS.WRITE:
             with open(dest, "wb") as f, artifact.file as af: