K 10
svn:author
V 5
gibbs
K 8
svn:date
V 27
2012-03-01T19:09:28.538021Z
K 7
svn:log
V 4018
MFC r231743,231836-231837,231839,231883,232308
    Xen PV block interface enhancements

Approved by:  re (kib)
Reviewed by:  cperciva
Tested by:    cperciva
Sponsored by: Spectra Logic Corporation

r231743
=======
Enhance documentation, improve interoperability, and fix defects in
FreeBSD's front and back Xen blkif interface drivers.

sys/dev/xen/blkfront/block.h:
sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkback/blkback.c:
	Replace FreeBSD specific multi-page ring impelementation with
	support for both the Citrix and Amazon/RedHat versions of this
	extension.

sys/dev/xen/blkfront/blkfront.c:
	o Add a per-instance sysctl tree that exposes all negotiated
	  transport parameters (ring pages, max number of requests,
	  max request size, max number of segments).
	o In blkfront_vdevice_to_unit() add a missing return statement
	  so that we properly identify the unit number for high numbered
	  xvd devices.

sys/dev/xen/blkback/blkback.c:
	o Add static dtrace probes for several events in this driver.
	o Defer connection shutdown processing until the front-end
	  enters the closed state.  This avoids prematurely tearing
	  down the connection when buggy front-ends transition to the
	  closing state, even though the device is open and they
	  veto the close request from the tool stack.
	o Add nodes for maximum request size and the number of active
	  ring pages to the exising, per-instance, sysctl tree.
	o Miscelaneous style cleanup.

sys/xen/interface/io/blkif.h:
	o Add extensive documentation of the XenStore nodes used to
	  implement the blkif interface.
	o Document the startup sequence between a front and back driver.
	o Add structures and documenatation for the "discard" feature
	  (AKA Trim).
	o Cleanup some definitions related to FreeBSD's request
	  number/size/segment-limit extension.

sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkback/blkback.c:
sys/xen/xenbus/xenbusvar.h:
	Add the convenience function xenbus_get_otherend_state() and
	use it to simplify some logic in both block-front and block-back.

r231836
=======
Fix "_" vs. "-" typo in a comment.  No functional changes.

r231837
=======
Fix typo in a printf string: "specificed" -> "specified".

r231839
=======
Fix a bug in the calculation of the maximum I/O request size.
The previous code did not limit the I/O request size based on
the maximum number of segments supported by the back-end.  In
current practice, since the only back-end supporting chained
requests is the FreeBSD implementation, this limit was never
exceeded.

sys/dev/xen/blkfront/block.h:
	Add two macros, XBF_SEGS_TO_SIZE() and XBF_SIZE_TO_SEGS(),
	to centralize the logic of reserving a segment to deal with
	non-page-aligned I/Os.

sys/dev/xen/blkfront/blkfront.c:
	o When negotiating transfer parameters, limit the
	  max_request_size we use and publish, if it is greater
	  than the maximum, unaligned, I/O we can support with
	  the number of segments advertised by the backend.
	o Don't unilaterally reduce the I/O size published to
	  the disk layer by a single page.  max_request_size
	  is already properly limited in the transfer parameter
	  negotiation code.
	o Fix typos in printf strings:
		"max_requests_segments" -> "max_request_segments"
		"specificed" -> "specified"

r231883
=======
Fix regression in the handling of blkback close events for
devices that are unplugged via QEMU.

sys/dev/xen/blkback/blkback.c:
	Toolstack initiated closures change the frontend's state
	to Closing.  The backend must change to Closing as well,
	even if we can't actually close yet, in order for the
	frontend to notice and start the closing process.

r232308
=======
blkif interface comment cleanups.  No functional changes

sys/xen/interface/io/blkif.h:
	o Insert space in "Red Hat".
	o Fix typo "discard-aligment" -> "discard-alignment"
	o Fix typo "unamp" -> "unmap"
	o Fix typo "formated" -> "formatted"
	o Clarify the text for "params".
	o Clarify the text for "sector-size".
	o Clarify the text for "max-requests" in the backend section.

END