[gnome-disk-utility/kailueke/auto-max-size: 2/2] Use special parameter when requesting the maximal partition size

[Kai Lüke <kailueke src gnome org>]

commit d3dce3a8cec638ab7a5d2be6514d601598d9e900
Author: Kai Lüke <kailueke riseup net>
Date:   Sat Jul 11 01:44:50 2020 +0200

    Use special parameter when requesting the maximal partition size
    
    This is a workaround and it would be nice to either handle this better
    in libblockdev or by creating the partition and then shrinking it.
    As having multiple GB partitions is common, I think the corner case can
    be ignored for now but it should be documented in the code.
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-disk-utility/-/issues/138

 src/disks/gducreateformatdialog.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
---
diff --git a/src/disks/gducreateformatdialog.c b/src/disks/gducreateformatdialog.c
index c93f3e01..453e9fd2 100644
--- a/src/disks/gducreateformatdialog.c
+++ b/src/disks/gducreateformatdialog.c
@@ -368,6 +368,22 @@ finish_cb (GtkDialog *dialog, gint response_id, CreateFormatData *data) /* the a
         }
 
       size = gdu_create_partition_page_get_size (data->partition_page);
+      /* Normal alignments of a few MB are expected to happen and normally it works well
+       * to pass a slightly larger size.
+       * Yet sometimes there are huge amounts of alignment enforced by libblockdev/libparted
+       * and it's unclear how many MB should be left when creating a partition on a 1 TB
+       * drive. The maximal size we present to the user is based on the size of unallocated
+       * space which may be too large.
+       * To address this issue, rely on the maximal size being found automatically by passing
+       * the special argument 0.
+       * However, this won't cover cases where the user substracts a few MB and now wonders
+       * why the partition can't be created. Heuristics for these corner cases could be
+       * implemented or libblockdev improved to handle these cases better but it would be
+       * easier and more accurate to create a partition with a maximal size first and then
+       * shrink it to the user's desired size if needed.
+       */
+      if (size == data->add_partition_maxsize)
+        size = 0;
       udisks_partition_table_call_create_partition (data->table,
                                                     data->add_partition_offset,
                                                     size,