[gparted] Report busy status of jbds (#89)

[Curtis Gedak <gedakc src gnome org>]

commit 1950a7a09d53fdedbf70e1b0a854302a9c4ca832
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue Jan 25 22:31:55 2022 +0000

    Report busy status of jbds (#89)
    
    Continuing from the state in the previous commit, create an ext4 file
    system using the previously created external journal and mount it.
        # mke2fs -t ext4 -J device=/dev/sdb1 -L test-ext4 /dev/sdb2
        # mount /dev/sdb2 /mnt/2
    
    Did some experimenting with trying to create a second file system using
    the same external journal which is already in use.
        # mke2fs -t ext4 -J device=/dev/sdb1 -L 2nd-test-ext4 /dev/sdb3
        ...
        /dev/sdb1 is apparently in use by the system; will not make a journal here!
        # exit $?
        1
    
    Examined the source code of mke2fs and found that it performs an
    exclusive read-only open of the named journal block device to check if
    it is in use by the system or not [1].  Use the same method in GParted.
    
    Not used alternative method would be to mark the jbd active when the
    ext3/4 file system using it is active, but that requires working out the
    linkage between them.  That can be done using either blkid or dumpe2fs
    output but that involves parsing more fields and caching more data so is
    much more code than just testing the block device busy status using the
    same method which mke2fs uses.
    
    Matching UUIDs via blkid output.
        # blkid /dev/sdb1 /dev/sdb2
        /dev/sdb1: LABEL="test-jbd" UUID="6e52858e-0479-432f-80a1-de42f9a4093e" TYPE="jbd"
        /dev/sdb2: LABEL="test-ext4" UUID="cea5c2cd-b21c-4abf-a497-8c073bb12300" 
EXT_JOURNAL="6e52858e-0479-432f-80a1-de42f9a4093e" TYPE="ext4"
    
    Matching UUIDs via dumpe2fs output.
        # dumpe2fs -h /dev/sdb1 | egrep 'Filesystem UUID|Journal users'
        dumpe2fs 1.46.3 (27-Jul-2021)
        Filesystem UUID:          6e52858e-0479-432f-80a1-de42f9a4093e
        Journal users:            cea5c2cd-b21c-4abf-a497-8c073bb12300
        # dumpe2fs -h /dev/sdb2 | egrep 'Filesystem UUID|Journal UUID'
        dumpe2fs 1.46.3 (27-Jul-2021)
        Filesystem UUID:          cea5c2cd-b21c-4abf-a497-8c073bb12300
        Journal UUID:             6e52858e-0479-432f-80a1-de42f9a4093e
    
    If GParted was going to show the journal to file system linkage in the
    UI then doing this would be needed.  However so far there has only been
    a single reported case of a GParted user using an external journal,
    therefore adding the code complexity for this feature is not currently
    justified.  The simple busy detection method used by mke2fs is all that
    is needed.
    
    [1] mke2fs source code
        https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git/
        misc/mke2fs.c:main()
            check_mount(journal_device, force, _("journal"));
        misc/util.c:check_mount()
            ext2fs_check_if_mounted(device, &mount_flags);
        lib/ext2fs/ismounted.c:ext2fs_check_if_mounted()
            ext2fs_check_mount_point(file, mount_flags, NULL, 0);
        lib/ext2fs/ismounted.c:ext2fs_check_if_mounted()
            if (stat(device, &st_buf) == 0 &&
                ext2fsP_is_disk_device(st_buf.st_mode)) {
                    int fd = open(device, O_RDONLY | O_EXCL);
                    if (fd >= 0) {
                            /*
                             * The device is not busy so it's
                             * definitelly not mounted. No need to
                             * to perform any more checks.
                             */
                            close(fd);
                            *mount_flags = 0;
                            return 0;
                    } else if (errno == EBUSY) {
                            busy = 1;
                    }
            }
    
    Closes #89 - GParted doesn't recognise EXT4 fs journal partition

 include/Utils.h              |  1 +
 src/Dialog_Partition_Info.cc |  6 ++++--
 src/GParted_Core.cc          |  1 +
 src/Utils.cc                 | 14 ++++++++++++++
 4 files changed, 20 insertions(+), 2 deletions(-)
---
diff --git a/include/Utils.h b/include/Utils.h
index dec562b0..477411e6 100644
--- a/include/Utils.h
+++ b/include/Utils.h
@@ -183,6 +183,7 @@ public:
        static int get_mounted_filesystem_usage( const Glib::ustring & mountpoint,
                                                 Byte_Value & fs_size, Byte_Value & fs_free,
                                                 Glib::ustring & error_message ) ;
+       static bool is_dev_busy(const Glib::ustring& path);
        static Byte_Value floor_size( Byte_Value value, Byte_Value rounding_size ) ;
        static Byte_Value ceil_size( Byte_Value value, Byte_Value rounding_size ) ;
 
diff --git a/src/Dialog_Partition_Info.cc b/src/Dialog_Partition_Info.cc
index b98ef102..0f8c3f36 100644
--- a/src/Dialog_Partition_Info.cc
+++ b/src/Dialog_Partition_Info.cc
@@ -341,7 +341,8 @@ void Dialog_Partition_Info::Display_Info()
                                 filesystem_ptn.fstype == FS_LINUX_SWRAID ||
                                 filesystem_ptn.fstype == FS_ATARAID      ||
                                 filesystem_ptn.fstype == FS_LVM2_PV      ||
-                                filesystem_ptn.fstype == FS_BCACHE         )
+                                filesystem_ptn.fstype == FS_BCACHE       ||
+                                filesystem_ptn.fstype == FS_JBD            )
                        {
                                /* TO TRANSLATORS:  Active
                                 * means that this linux swap, linux software raid partition, or
@@ -376,7 +377,8 @@ void Dialog_Partition_Info::Display_Info()
                else if (filesystem_ptn.fstype == FS_LINUX_SWAP   ||
                         filesystem_ptn.fstype == FS_LINUX_SWRAID ||
                         filesystem_ptn.fstype == FS_ATARAID      ||
-                        filesystem_ptn.fstype == FS_BCACHE         )
+                        filesystem_ptn.fstype == FS_BCACHE       ||
+                        filesystem_ptn.fstype == FS_JBD            )
                {
                        /* TO TRANSLATORS:  Not active
                         *  means that this linux swap or linux software raid partition
diff --git a/src/GParted_Core.cc b/src/GParted_Core.cc
index 6dec0e1f..2e1ed2f4 100644
--- a/src/GParted_Core.cc
+++ b/src/GParted_Core.cc
@@ -1607,6 +1607,7 @@ bool GParted_Core::is_busy(const Glib::ustring& device_path, FSType fstype, cons
                busy |= (fstype == FS_ATARAID      && (SWRaid_Info::is_member_active(partition_path) ||
                                                       dmraid.is_member_active(partition_path)         ));
                busy |= (fstype == FS_BCACHE       && BCache_Info::is_active(device_path, partition_path));
+               busy |= (fstype == FS_JBD          && Utils::is_dev_busy(partition_path));
        }
 
        return busy ;
diff --git a/src/Utils.cc b/src/Utils.cc
index 707e4bc1..f3f3b281 100644
--- a/src/Utils.cc
+++ b/src/Utils.cc
@@ -929,6 +929,20 @@ int Utils::get_mounted_filesystem_usage( const Glib::ustring & mountpoint,
        return ret ;
 }
 
+
+// Report whether the kernel considers the device busy or not.
+bool Utils::is_dev_busy(const Glib::ustring& path)
+{
+       int fd = open(path.c_str(), O_RDONLY|O_EXCL);
+       if (fd == -1 && errno == EBUSY)
+               return true;
+       else if (fd >= 0)
+               close(fd);
+
+       return false;
+}
+
+
 //Round down to multiple of rounding_size
 Byte_Value Utils::floor_size( Byte_Value value, Byte_Value rounding_size )
 {