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Age	Commit message (Collapse)	Author	Files	Lines
2018-06-29	block: Convert .bdrv_truncate callback to coroutine_fn	Kevin Wolf	1	-4/+4
	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>
2018-05-15	block: Support BDRV_REQ_WRITE_UNCHANGED in filters	Max Reitz	1	-4/+6
	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	block: Add COR filter driver	Max Reitz	1	-0/+171
	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>