Commit 0b9e918f authored by Kevin Wolf's avatar Kevin Wolf
Browse files

fdc: Fix inserting read-only media in empty drive 



In order to insert a read-only medium (i.e. a read-only block node) to
the BlockBackend of a floppy drive, we must not have taken write
permissions on that BlockBackend, or the operation will fail with the
error message "Block node is read-only".

The device already takes care to remove all permissions when the medium
is ejected, but the state isn't correct if the drive is initially empty:
It uses blk_is_read_only() to check whether write permissions should be
taken, but this function returns false for empty BlockBackends in the
common case.

Fix floppy_drive_realize() to avoid taking write permissions if the
drive is empty.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarJohn Snow <jsnow@redhat.com>
parent 8517bf84

hw/block/fdc.c

+8 −3
Original line number Diff line number Diff line
@@ -514,6 +514,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp) 
    FloppyDrive *dev = FLOPPY_DRIVE(qdev);

    FloppyBus *bus = FLOPPY_BUS(qdev->parent_bus);

    FDrive *drive;

    bool read_only;

    int ret;



    if (dev->unit == -1) {
@@ -542,6 +543,12 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp) 
        dev->conf.blk = blk_new(qemu_get_aio_context(), 0, BLK_PERM_ALL);

        ret = blk_attach_dev(dev->conf.blk, qdev);

        assert(ret == 0);



        /* Don't take write permissions on an empty drive to allow attaching a

         * read-only node later */

        read_only = true;

    } else {

        read_only = !blk_bs(dev->conf.blk) || blk_is_read_only(dev->conf.blk);

    }



    blkconf_blocksizes(&dev->conf);
@@ -559,9 +566,7 @@ static void floppy_drive_realize(DeviceState *qdev, Error **errp) 
    dev->conf.rerror = BLOCKDEV_ON_ERROR_AUTO;

    dev->conf.werror = BLOCKDEV_ON_ERROR_AUTO;



    if (!blkconf_apply_backend_options(&dev->conf,

                                       blk_is_read_only(dev->conf.blk),

                                       false, errp)) {

    if (!blkconf_apply_backend_options(&dev->conf, read_only, false, errp)) {

        return;

    }