[gentoo-catalyst] [PATCH 03/12] catalyst: Use libmount for handling mounts

[Matt Turner <mattst88@gentoo.org>]

Handle the mounts/unmounts in all in process rather than shelling out
(pun intended!) to an external program.

While we're here, change some log.notice to log.debug since those cases
are normal and expected.

Signed-off-by: Matt Turner <mattst88@gentoo.org>
---
 catalyst/base/stagebase.py | 57 +++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/catalyst/base/stagebase.py b/catalyst/base/stagebase.py
index e71ce344..73eacfbe 100644
--- a/catalyst/base/stagebase.py
+++ b/catalyst/base/stagebase.py
@@ -6,6 +6,7 @@ import sys
 
 from pathlib import Path
 
+import libmount
 import toml
 
 from snakeoil import fileutils
@@ -853,7 +854,8 @@ class StageBase(TargetBase, ClearBase, GenBase):
 
             source = str(self.mount[x]['source'])
             target = self.settings['chroot_path'] + str(self.mount[x]['target'])
-            mount = ['mount']
+            fstype = ''
+            options = ''
 
             log.debug('bind %s: "%s" -> "%s"', x, source, target)
 
@@ -861,18 +863,20 @@ class StageBase(TargetBase, ClearBase, GenBase):
                 if 'var_tmpfs_portage' not in self.settings:
                     continue
 
-                mount += ['-t', 'tmpfs', '-o',
-                          f"size={self.settings['var_tmpfs_portage']}G"]
+                fstype = 'tmpfs'
+                options = f"size={self.settings['var_tmpfs_portage']}G"
             elif source == 'tmpfs':
-                mount += ['-t', 'tmpfs']
+                fstype = 'tmpfs'
             elif source == 'shm':
-                mount += ['-t', 'tmpfs', '-o', 'noexec,nosuid,nodev']
+                fstype = 'tmpfs'
+                options = 'noexec,nosuid,nodev'
             else:
                 source_path = Path(self.mount[x]['source'])
                 if source_path.suffix == '.sqfs':
-                    mount += ['-o', 'ro']
+                    fstype = 'squashfs'
+                    options = 'ro,loop'
                 else:
-                    mount.append('--bind')
+                    options = 'bind'
 
                     # We may need to create the source of the bind mount. E.g., in the
                     # case of an empty package cache we must create the directory that
@@ -881,38 +885,47 @@ class StageBase(TargetBase, ClearBase, GenBase):
 
             Path(target).mkdir(mode=0o755, parents=True, exist_ok=True)
 
-            cmd(mount + [source, target], env=self.env, fail_func=self.unbind)
+            try:
+                cxt = libmount.Context(source=source, target=target,
+                                       fstype=fstype, options=options)
+                cxt.mount()
+            except OSError as e:
+                self.unbind()
+                raise CatalystError(f"Couldn't mount: {source}, {e.strerror}")
 
     def unbind(self):
-        ouch = 0
-        mypath = self.settings["chroot_path"]
+        chroot_path = self.settings["chroot_path"]
+        umount_failed = False
 
         # Unmount in reverse order
-        for x in [x for x in reversed(self.mount) if self.mount[x]['enable']]:
-            target = normpath(mypath + self.mount[x]['target'])
-            if not os.path.exists(target):
-                log.notice('%s does not exist. Skipping', target)
+        for target in [Path(chroot_path + self.mount[x]['target'])
+                       for x in reversed(self.mount)
+                       if self.mount[x]['enable']]:
+            if not target.exists():
+                log.debug('%s does not exist. Skipping', target)
                 continue
 
             if not ismount(target):
-                log.notice('%s is not a mount point. Skipping', target)
+                log.debug('%s is not a mount point. Skipping', target)
                 continue
 
             try:
-                cmd(['umount', target], env=self.env)
-            except CatalystError:
+                cxt = libmount.Context(target=str(target))
+                cxt.umount()
+            except OSError:
                 log.warning('First attempt to unmount failed: %s', target)
                 log.warning('Killing any pids still running in the chroot')
 
                 self.kill_chroot_pids()
 
                 try:
-                    cmd(['umount', target], env=self.env)
-                except CatalystError:
-                    ouch = 1
-                    log.warning("Couldn't umount bind mount: %s", target)
+                    cxt.umount()
+                except OSError as e:
+                    umount_failed = True
+                    log.warning("Couldn't umount: %s, %s", target,
+                                e.strerror)
 
-        if ouch:
+        if umount_failed:
             # if any bind mounts really failed, then we need to raise
             # this to potentially prevent an upcoming bash stage cleanup script
             # from wiping our bind mounts.
-- 
2.26.2