Split the metadata commit in two parts:
1. dm_clone_metadata_pre_commit(): Prepare the current transaction for
committing. After this is called, all subsequent metadata updates,
done through either dm_clone_set_region_hydrated() or
dm_clone_cond_set_range(), will be part of the next transaction.
2. dm_clone_metadata_commit(): Actually commit the current transaction
to disk and start a new transaction.
This is required by the following commit. It allows dm-clone to flush
the destination device after step (1) to ensure that all freshly
hydrated regions, for which we are updating the metadata, are properly
written to non-volatile storage and won't be lost in case of a crash.
Fixes: 7431b7835f ("dm: add clone target")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Extend struct dirty_map with a second bitmap which tracks the exact
regions that were hydrated during the current metadata transaction.
Moreover, fix __flush_dmap() to only commit the metadata of the regions
that were hydrated during the current transaction.
This is required by the following commits to fix a data corruption bug.
Fixes: 7431b7835f ("dm: add clone target")
Cc: stable@vger.kernel.org # v5.4+
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
If we are in a place where it is known that interrupts are enabled,
functions spin_lock_irq/spin_unlock_irq should be used instead of
spin_lock_irqsave/spin_unlock_irqrestore.
spin_lock_irq and spin_unlock_irq are faster because they don't need to
push and pop the flags register.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Add the dm-clone target, which allows cloning of arbitrary block
devices.
dm-clone produces a one-to-one copy of an existing, read-only source
device into a writable destination device: It presents a virtual block
device which makes all data appear immediately, and redirects reads and
writes accordingly.
The main use case of dm-clone is to clone a potentially remote,
high-latency, read-only, archival-type block device into a writable,
fast, primary-type device for fast, low-latency I/O. The cloned device
is visible/mountable immediately and the copy of the source device to
the destination device happens in the background, in parallel with user
I/O.
When the cloning completes, the dm-clone table can be removed altogether
and be replaced, e.g., by a linear table, mapping directly to the
destination device.
For further information and examples of how to use dm-clone, please read
Documentation/admin-guide/device-mapper/dm-clone.rst
Suggested-by: Vangelis Koukis <vkoukis@arrikto.com>
Co-developed-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Nikos Tsironis