Lennart Poettering
7f52206a2b
Let's rework how we lock loopback block devices in two ways: 1. Lock a separate fd, instead of the main block device fd. We already did that for our internal locking when allocating loopback block devices, but do so for the exposed locking (i.e. loop_device_flock()), too, so that the lock is independent of the main fd we actually use of IO. 2. Instead of locking the device during allocation of the loopback device, then unlocking it (which will make udev run), and then re-locking things if we need, let's instead just keep the lock the whole time, to make things a bit safer and faster, and not have to wait for udev at all. This is done by adding a "lock_op" parameter to loop device allocation functions that declares the initial state of the lock, and is one of LOCK_UN/LOCK_SH/LOCK_EX. This change also shortens a lot of code, since we allocate + immediately lock loopback devices pretty much everywhere.
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