[PATCH 4/15] block copy: use a timer to fix a theoretical deadlock

The block layer creates two bios for each copy operation. The bios travel independently through the storage stack and they are paired at the block device. There is a theoretical problem with this - the block device stack only guarantees forward progress for a single bio. When two bios are sent,

[PATCH 4/15] block copy: use a timer to fix a theoretical deadlock

The block layer creates two bios for each copy operation. The bios travel independently through the storage stack and they are paired at the block device. There is a theoretical problem with this - the block device stack only guarantees forward progress for a single bio. When two bios are sent,