[gparted] Limit maximum ext2/3/4 volume size to just less than 16 TiB (#766910)

[Curtis Gedak <gedakc src gnome org>]

commit af17808d08c762b1c3b6093211a91290df2c993e
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sat May 28 20:29:27 2016 +0100

    Limit maximum ext2/3/4 volume size to just less than 16 TiB (#766910)
    
    Maximum size of an ext2/3/4 volume is 2^32 - 1 blocks [1], ignoring ext4
    with 64bit feature.  That is just under 16 TiB with a 4K block size.
    
        # truncate -s 16T /mnt/1/sparse.img
        # ls -l /mnt/1/sparse.img
        -rw-r--r--. 1 root root 17592186044416 May 28 19:33 /mnt/1/sparse.img
        # losetup /dev/loop0 /mnt/1/sparse.img
        # mkfs.ext3 /dev/loop0
        mke2fs 1.43 (17-May-2016)
        mkfs.ext3: Size of device (0x100000000 blocks) /dev/loop0 too big to be expressed
                in 32 bits using a blocksize of 4096.
        # losetup -d /dev/loop0
        #
        #
        # truncate -s $((16*1024**3-4))K sparse.img
        # ls -l /mnt/1/sparse.img
        -rw-r--r--. 1 root root 17592186040320 May 28 19:51 /mnt/1/sparse.img
        # losetup /dev/loop0 /mnt/1/sparse.img
        # mkfs.ext3 /dev/loop0
        mke2fs 1.43 (17-May-2016)
        Discarding device blocks: done
        Creating filesystem with 4294967295 4k blocks and 536870912 inodes
        Filesystem UUID: 9721d8d9-8711-499b-aae4-8ea4d9e16ca2
        Superblock backups stored on blocks:
                32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
                4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
                102400000, 214990848, 512000000, 550731776, 644972544, 1934917632,
                2560000000, 3855122432
    
        Allocating group tables: done
        Writing inode tables: done
        Creating journal (32768 blocks): done
        Writing superblocks and filesystem accounting information: done
    
        # losetup -d /dev/loop0
        # rm /mnt/1/sparse.img
    
    Actually limit the maximum volume size to 1 MiB less than 16 TiB for
    coding reasons explained in the FIXME comment.
    
    [1] Ext4 Disk Layout, Blocks
        https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Blocks
    
    Bug 766910 - Multiple boot loaders don't work on 64bit EXT4 file systems

 src/ext2.cc |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/src/ext2.cc b/src/ext2.cc
index e3736d0..8952e48 100644
--- a/src/ext2.cc
+++ b/src/ext2.cc
@@ -114,6 +114,16 @@ FS ext2::get_filesystem_support()
                if ( specific_type != FS_EXT2 && Utils::kernel_version_at_least( 3, 6, 0 ) )
                        fs .online_grow = fs .grow ;
 #endif
+
+               // Maximum size of an ext2/3/4 volume is 2^32 - 1 blocks, ignoring ext4
+               // with 64bit feature.  That is just under 16 TiB with a 4K block size.
+               // *   Ext4 Disk Layout, Blocks
+               //     https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Blocks
+               // FIXME: Rounding down to whole MiB here should not be necessary.  The
+               // Copy, New and Resize/Move dialogs should limit FS correctly without
+               // this.  See bug #766910 comment #12 onwards for further discussion.
+               //     https://bugzilla.gnome.org/show_bug.cgi?id=766910#c12
+               fs.MAX = Utils::floor_size( 16 * TEBIBYTE - 4 * KIBIBYTE, MEBIBYTE );
        }
 
        return fs ;