This series of patches reimplements the way rbd requests are managed. The motivation for doing this is that the existing code assumes in places that every I/O request was associated with a Linux request initiated from the block layer. In order to support layered rbd images, we need to initiate rbd image requests within rbd. In addition, the size of an rbd object in a parent image could be smaller than the object size in the child. That means satisfying a request to a single object in the child image may require issuing requests to multiple objects in the parent. This too was not easily supported by the existing code. In this new code, we distinguish between an "image request" and an "object request." An image request is an I/O operation defined in terms of an entire rbd image--its offset and length are relative to the image as a whole. An object request is a request targeted at a single rbd object. An image request is implemented using one or more object requests, but individual object requests can also be used for doing things like reading or operating on the rbd image header object. The new code also more clearly separates itself from the osd client, especially with respect to request completion. Each object request supplies a common callback function with its osd client request. This callback handles certain rbd-specific tasks, like zero-filling portions of a read buffer that were not supplied by the. A simple wait routine is now supplied to allow synchronous completion of an object request. This set of changes is available in the ceph-client git repository branch "wip-rbd-review". That branch also begins with three unrelated commits (which I recently posted for review) and ends with two others (which are temporary and there only to test with version 2 image support enabled). -Alex [PATCH 01/12] rbd: new request tracking code [PATCH 02/12] rbd: kill rbd_rq_fn() and all other related code [PATCH 03/12] rbd: kill rbd_req_coll and rbd_request [PATCH 04/12] rbd: implement sync object read with new code [PATCH 05/12] rbd: get rid of rbd_req_sync_read() [PATCH 06/12] rbd: implement watch/unwatch with new code [PATCH 07/12] rbd: get rid of rbd_req_sync_watch() [PATCH 08/12] rbd: use new code for notify ack [PATCH 09/12] rbd: get rid of rbd_req_sync_notify_ack() [PATCH 10/12] rbd: send notify ack asynchronously [PATCH 11/12] rbd: implement sync method with new code [PATCH 12/12] rbd: get rid of rbd_req_sync_exec() -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
