From a7bc882aa506b11b85fd49aa4768158c20f3f4ff Mon Sep 17 00:00:00 2001
From: Mike McLean <mikem@redhat.com>
Date: Mon, 5 May 2025 18:19:45 -0400
Subject: [PATCH] initial fix

---
 kojihub/kojihub.py                   | 74 +++++++++++++++++++++++++---
 tests/test_hub/test_promote_build.py |  6 +--
 2 files changed, 69 insertions(+), 11 deletions(-)

diff --git a/kojihub/kojihub.py b/kojihub/kojihub.py
index 8c90ef7a..69e17767 100644
--- a/kojihub/kojihub.py
+++ b/kojihub/kojihub.py
@@ -6265,6 +6265,72 @@ def ensure_volume_symlink(binfo):
     os.symlink(relpath, basedir)
 
 
+def ensure_volume_backlink(new_binfo, old_binfo):
+    """Ensure we have a link for a build on given non-default volume
+
+    We point the symlink at the default volume location, because this path should
+    always be either valid symlink or the actual build dir.
+
+    Note: this is tricky!
+    We primarily use relative symlinks under /mnt/koji, however this can break
+    when crossing volumes. In general, /mnt/koji/vol/foo/.. != /mnt/koji/vol
+    However, relpath() assumes this is the case because it is "a path computation"
+    """
+
+    # basic checks
+    volname = old_binfo['volume_name']
+    if volname == 'DEFAULT':
+        # nothing to do
+        # default volume symlinks are handled in ensure_volume_symlink()
+        return
+    voldir = koji.pathinfo.volumedir(volname)
+    if not os.path.isdir(voldir):
+        raise koji.GenericError('Missing volume dir: %s' % voldir)
+
+    # ensure we have the volume toplink
+    toplink = joinpath(voldir, 'toplink')
+    if os.path.islink(toplink):
+        if not os.path.exists(toplink):
+            raise koji.GenericError(f'Bad volume toplink: {toplink}')
+    elif os.path.exists(toplink):
+        # not a link
+        raise koji.GenericError(f'Not a symlink: {toplink}')
+    else:
+        # in the future, this should be part of volume setup, but for now
+        # we'll be nice and create it
+        target = koji.pathinfo.topdir
+        logger.warning('No toplink for volume. Creating {toplink} -> {target}')
+        os.symlink(target, toplink)
+
+    # get the old build path (where we will place the symlink)
+    olddir = koji.pathinfo.build(old_binfo)
+
+    # construct the relative path in parts
+    # - relpath to voldir
+    # - voldir/toplink is a symlink to topdir
+    # - relpath from topdir to olddir
+    path1 = os.path.relpath(voldir, os.path.dirname(olddir))  # should be ../../..
+    assert path1 == '../../..'  # XXX
+    relpathinfo = koji.PathInfo(topdir='toplink')
+    base_binfo = new_binfo.copy()
+    base_binfo['volume_name'] = 'DEFAULT'
+    path2 = relpathinfo.build(base_binfo)  # toplink/packages/N/V/R
+
+    # check/make the symlink
+    relpath = joinpath(path1, path2)
+    if os.path.islink(olddir):
+        if os.readlink(olddir) == relpath:
+            # already correct
+            return
+        os.unlink(olddir)
+    elif os.path.exists(olddir):
+        raise koji.GenericError('Unexpected build content: %s' % olddir)
+    else:
+        # parent dir might not exist
+        koji.ensuredir(os.path.dirname(olddir))
+    os.symlink(relpath, olddir)
+
+
 def check_volume_policy(data, strict=False, default=None):
     """Check volume policy for the given data
 
@@ -10681,13 +10747,7 @@ def _promote_build(build, force=False):
 
     # provide a symlink at original draft location
     # we point to the default volume in case the build moves in the future
-    base_vol = lookup_name('volume', 'DEFAULT', strict=True)
-    base_binfo = new_binfo.copy()
-    base_binfo['volume_id'] = base_vol['id']
-    base_binfo['volume_name'] = base_vol['name']
-    basedir = koji.pathinfo.build(base_binfo)
-    relpath = os.path.relpath(basedir, os.path.dirname(oldpath))
-    os.symlink(relpath, oldpath)
+    ensure_volume_backlink(new_binfo, binfo)
 
     # apply volume policy in case it's changed by release update.
     apply_volume_policy(new_binfo, strict=False)
diff --git a/tests/test_hub/test_promote_build.py b/tests/test_hub/test_promote_build.py
index 4ca6e7d3..bc4e4e6b 100644
--- a/tests/test_hub/test_promote_build.py
+++ b/tests/test_hub/test_promote_build.py
@@ -34,6 +34,7 @@ class TestPromoteBuild(unittest.TestCase):
                                               return_value=None).start()
         self.safer_move = mock.patch('kojihub.kojihub.safer_move').start()
         self.ensure_volume_symlink = mock.patch('kojihub.kojihub.ensure_volume_symlink').start()
+        self.ensure_volume_backlink = mock.patch('kojihub.kojihub.ensure_volume_backlink').start()
         self.lookup_name = mock.patch('kojihub.kojihub.lookup_name',
                                       return_value={'id': 1, 'name': 'DEFAULT'}).start()
         self.os_symlink = mock.patch('os.symlink').start()
@@ -94,10 +95,7 @@ class TestPromoteBuild(unittest.TestCase):
             '/mnt/koji/vol/X/packages/foo/bar/tgtrel,draft_1',
             '/mnt/koji/vol/X/packages/foo/bar/tgtrel'
         )
-        self.os_symlink.assert_called_once_with(
-            '../../../../../packages/foo/bar/tgtrel',
-            '/mnt/koji/vol/X/packages/foo/bar/tgtrel,draft_1'
-        )
+        self.os_symlink.assert_not_called()
 
     def test_promote_build_not_draft(self):
         self.get_build.return_value = {'draft': False, 'nvr': 'testnvr'}