[gparted] Create loop devices for BTRFS read file system interface tests (!49)

[Curtis Gedak <gedakc src gnome org>]

commit 07ad43a1072a104543bfc45bc5d357f3d8f8d6f6
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Wed Oct 9 13:35:17 2019 +0100

    Create loop devices for BTRFS read file system interface tests (!49)
    
    For BTRFS the read (and resize) tests fail when using an image file,
    however the create, write and check tests pass.  Selected output from
    the test program:
    
        $ ./test_SupportedFileSystems --gtest_filter='*/btrfs' | fgrep ' ms'
        [       OK ] My/SupportedFileSystemsTest.Create/btrfs (43 ms)
        [  FAILED  ] My/SupportedFileSystemsTest.CreateAndReadUsage/btrfs, where GetParam() = 7 (95 ms)
        [  FAILED  ] My/SupportedFileSystemsTest.CreateAndReadLabel/btrfs, where GetParam() = 7 (158 ms)
        [  FAILED  ] My/SupportedFileSystemsTest.CreateAndReadUUID/btrfs, where GetParam() = 7 (164 ms)
        [       OK ] My/SupportedFileSystemsTest.CreateAndWriteLabel/btrfs (164 ms)
        [       OK ] My/SupportedFileSystemsTest.CreateAndWriteUUID/btrfs (132 ms)
        [       OK ] My/SupportedFileSystemsTest.CreateAndCheck/btrfs (129 ms)
        [       OK ] My/SupportedFileSystemsTest.CreateAndRemove/btrfs (0 ms)
        [  FAILED  ] My/SupportedFileSystemsTest.CreateAndGrow/btrfs, where GetParam() = 7 (155 ms)
        [  FAILED  ] My/SupportedFileSystemsTest.CreateAndShrink/btrfs, where GetParam() = 7 (97 ms)
        [----------] 10 tests from My/SupportedFileSystemsTest (1137 ms total)
        [==========] 10 tests from 1 test case ran. (1137 ms total)
    
    The read operations fail because 'btrfs filesystem show' doesn't work on
    am image file:
        $ truncate -s 256M test.img
        $ mkfs.btrfs test.img
        btrfs-progs v4.9.1
        See http://btrfs.wiki.kernel.org for more information.
    
        Label:              (null)
        UUID:               de1624ae-39bb-4796-aee4-7ee1fa24c06a
        Node side:          16384
        Sector size:        4096
        Filesystem size:    256.00MiB
        Block group profiles:
          Data:             single
          Metadata:         DUP
          System:           DUP
        SSD detected:       no
        Incompat features:  extref, skinny-metadata
        Number of devices:  1
        Devices:
            ID       SIZE  PATH
             1  256.00MiB  test.img
        $ btrfs filesystem show test.img
        ERROR: not a valid btrfs filesystem: /home/centos/programming/c/gparted/tests/test.img
        $ echo $1
        1
    
    Querying a BTRFS image file also fails as root:
        $ su
        Password:
        # btrfs filesystem show test.img
        ERROR: not a valid btrfs filesystem: /home/centos/programming/c/gparted/tests/test.img
        # echo $1
        1
    
    However querying the BTRFS via a loop device succeeds:
        # losetup --show --find test.img
        /dev/loop0
        # btrfs filesystem show /dev/loop0
        Label: none  uuid: de1624ae-39bb-4796-aee4-7ee1fa24c06a
                Total devices 1 FS bytes used 112.00KiB
                devid    1 size 256.00MiB used 88.00MiB path /root/test.img
    
    There must be some kernel level BTRFS file system device discovery
    happening because now after creating a loop device for the image file,
    the BTRFS can be shown via the image file directly:
        # btrfs filesystem show test.img
        Label: none  uuid: de1624ae-39bb-4796-aee4-7ee1fa24c06a
                Total devices 1 FS bytes used 112.00KiB
                devid    1 size 256.00MiB used 88.00MiB path /root/test.img
    
    Anyway for the BTRFS reading tests make them required a loop device and
    therefore root only.  Now these tests are skipped as non-root user and
    pass as root.
    
    Addressing BTRFS resizing test failures will be handled in a following
    commit.
    
    Closes !49 - Add file system interface tests

 tests/test_SupportedFileSystems.cc | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/tests/test_SupportedFileSystems.cc b/tests/test_SupportedFileSystems.cc
index 57ef1c54..39a23812 100644
--- a/tests/test_SupportedFileSystems.cc
+++ b/tests/test_SupportedFileSystems.cc
@@ -486,6 +486,7 @@ TEST_P(SupportedFileSystemsTest, CreateAndReadUsage)
 {
        SKIP_IF_FS_DOESNT_SUPPORT(create);
        SKIP_IF_FS_DOESNT_SUPPORT(read);
+       SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_BTRFS);
        SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_LVM2_PV);
 
        extra_setup();
@@ -514,6 +515,7 @@ TEST_P(SupportedFileSystemsTest, CreateAndReadLabel)
 {
        SKIP_IF_FS_DOESNT_SUPPORT(create);
        SKIP_IF_FS_DOESNT_SUPPORT(read_label);
+       SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_BTRFS);
        SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_LVM2_PV);
 
        const char* fs_label = "TEST_LABEL";
@@ -535,6 +537,7 @@ TEST_P(SupportedFileSystemsTest, CreateAndReadUUID)
 {
        SKIP_IF_FS_DOESNT_SUPPORT(create);
        SKIP_IF_FS_DOESNT_SUPPORT(read_uuid);
+       SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_BTRFS);
        SKIP_IF_NOT_ROOT_FOR_REQUIRED_LOOPDEV_FOR_FS(FS_LVM2_PV);
 
        extra_setup();