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fdc: Fix inserting read-only media in empty drive

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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: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
This commit is contained in:
Kevin Wolf 2019-07-30 15:37:08 +02:00
parent 8517bf8405
commit 0b9e918f03
1 changed files with 8 additions and 3 deletions
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11
hw/block/fdc.c
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@ -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;
}