fix(fs/_mount#_sync): use findmnt to check mount success (#4003)

Fixes #3973

@xen-orchestra/fs/src/_mount.js

@@ -86,12 +86,13 @@ export default class MountHandler extends LocalHandler {
         }
       )
     } catch (error) {
-      let stderr
-      if (
-        error == null ||
-        typeof (stderr = error.stderr) !== 'string' ||
-        !(stderr.includes('already mounted') || stderr.includes('busy'))
-      ) {
+      try {
+        // the failure may mean it's already mounted, use `findmnt` to check
+        // that's the case
+        await this._execa('findmnt', ['--target', realPath], {
+          stdio: 'ignore',
+        })
+      } catch (_) {
         throw error
       }
     }

CHANGELOG.unreleased.md

@@ -17,6 +17,7 @@
 - [Notifications] Fix invalid notifications when not registered (PR [#3966](https://github.com/vatesfr/xen-orchestra/pull/3966))
 - [Import] Fix import of some OVA files [#3962](https://github.com/vatesfr/xen-orchestra/issues/3962) (PR [#3974](https://github.com/vatesfr/xen-orchestra/pull/3974))
 - [Servers] Fix *already connected error* after a server has been removed during connection [#3976](https://github.com/vatesfr/xen-orchestra/issues/3976) (PR [#3977](https://github.com/vatesfr/xen-orchestra/pull/3977))
+- [Backup] Fix random _mount_ issues with NFS/SMB remotes [#3973](https://github.com/vatesfr/xen-orchestra/issues/3973) (PR [#4003](https://github.com/vatesfr/xen-orchestra/pull/4003))
 
 ### Released packages