Commit Graph

5 Commits

Author SHA1 Message Date
Vladimir Sementsov-Ogievskiy f66b1f0e27 block: drop empty .bdrv_close handlers
.bdrv_close handler is optional after previous commit, no needs to keep
empty functions more.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-08-15 12:50:39 +02:00
Fam Zheng 0b9fd3f467 block: Use BdrvChild to discard
Other I/O functions are already using a BdrvChild pointer in the API, so
make discard do the same. It makes it possible to initiate the same
permission checks before doing I/O, and much easier to share the
helper functions for this, which will be added and used by write,
truncate and copy range paths.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-07-10 16:01:52 +02:00
Kevin Wolf 061ca8a368 block: Convert .bdrv_truncate callback to coroutine_fn
bdrv_truncate() is an operation that can block (even for a quite long
time, depending on the PreallocMode) in I/O paths that shouldn't block.
Convert it to a coroutine_fn so that we have the infrastructure for
drivers to make their .bdrv_co_truncate implementation asynchronous.

This change could potentially introduce new race conditions because
bdrv_truncate() isn't necessarily executed atomically any more. Whether
this is a problem needs to be evaluated for each block driver that
supports truncate:

* file-posix/win32, gluster, iscsi, nfs, rbd, ssh, sheepdog: The
  protocol drivers are trivially safe because they don't actually yield
  yet, so there is no change in behaviour.

* copy-on-read, crypto, raw-format: Essentially just filter drivers that
  pass the request to a child node, no problem.

* qcow2: The implementation modifies metadata, so it needs to hold
  s->lock to be safe with concurrent I/O requests. In order to avoid
  double locking, this requires pulling the locking out into
  preallocate_co() and using qcow2_write_caches() instead of
  bdrv_flush().

* qed: Does a single header update, this is fine without locking.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2018-06-29 14:20:56 +02:00
Max Reitz 228345bf5d block: Support BDRV_REQ_WRITE_UNCHANGED in filters
Update the rest of the filter drivers to support
BDRV_REQ_WRITE_UNCHANGED.  They already forward write request flags to
their children, so we just have to announce support for it.

This patch does not cover the replication driver because that currently
does not support flags at all, and because it just grabs the WRITE
permission for its children when it can, so we should be fine just
submitting the incoming WRITE_UNCHANGED requests as normal writes.

It also does not cover format drivers for similar reasons.  They all use
bdrv_format_default_perms() as their .bdrv_child_perm() implementation
so they just always grab the WRITE permission for their file children
whenever possible.  In addition, it often would be difficult to
ascertain whether incoming unchanging writes end up as unchanging writes
in their files.  So we just leave them as normal potentially changing
writes.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20180421132929.21610-7-mreitz@redhat.com
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-05-15 16:15:21 +02:00
Max Reitz 6c6f24fd84 block: Add COR filter driver
This adds a simple copy-on-read filter driver.  It relies on the already
existing COR functionality in the central block layer code, which may be
moved here once we no longer need it there.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20180421132929.21610-2-mreitz@redhat.com
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-05-15 16:15:21 +02:00