From patchwork Mon Mar 10 07:26:04 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fam Zheng X-Patchwork-Id: 328473 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 5AC242C00D1 for ; Mon, 10 Mar 2014 18:31:58 +1100 (EST) Received: from localhost ([::1]:47093 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WMugm-00054L-7y for incoming@patchwork.ozlabs.org; Mon, 10 Mar 2014 03:31:56 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40477) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WMubl-0006e1-Ld for qemu-devel@nongnu.org; Mon, 10 Mar 2014 03:26:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WMubf-00079z-Kr for qemu-devel@nongnu.org; Mon, 10 Mar 2014 03:26:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53859) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WMubf-00079v-CN for qemu-devel@nongnu.org; Mon, 10 Mar 2014 03:26:39 -0400 Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s2A7Qbjl029868 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 10 Mar 2014 03:26:37 -0400 Received: from T430.nay.redhat.com ([10.66.6.152]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s2A7PtEv024065; Mon, 10 Mar 2014 03:26:33 -0400 From: Fam Zheng To: qemu-devel@nongnu.org Date: Mon, 10 Mar 2014 15:26:04 +0800 Message-Id: <1394436370-8908-9-git-send-email-famz@redhat.com> In-Reply-To: <1394436370-8908-1-git-send-email-famz@redhat.com> References: <1394436370-8908-1-git-send-email-famz@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: kwolf@redhat.com, benoit.canet@irqsave.net, rjones@redhat.com, jcody@redhat.com, armbru@redhat.com, ptoscano@redhat.com, imain@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Subject: [Qemu-devel] [PATCH v17 08/14] block: Support dropping active in bdrv_drop_intermediate X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Dropping intermediate could be useful both for commit and stream, and BDS refcnt plus bdrv_swap could do most of the job nicely. It also needs to work with op blockers. Signed-off-by: Fam Zheng --- block.c | 139 ++++++++++++++++++++++++++++----------------------------- block/commit.c | 2 +- 2 files changed, 70 insertions(+), 71 deletions(-) diff --git a/block.c b/block.c index 05f7766..0af7c62 100644 --- a/block.c +++ b/block.c @@ -2503,115 +2503,114 @@ BlockDriverState *bdrv_find_overlay(BlockDriverState *active, return overlay; } -typedef struct BlkIntermediateStates { - BlockDriverState *bs; - QSIMPLEQ_ENTRY(BlkIntermediateStates) entry; -} BlkIntermediateStates; - - /* - * Drops images above 'base' up to and including 'top', and sets the image - * above 'top' to have base as its backing file. + * Drops images above 'base' up to and including 'top', and sets new 'base' as + * backing_hd of top's overlay (the image orignally has 'top' as backing file). + * top's overlay may be NULL if 'top' is active, no such update needed. + * Requires that the top's overlay to 'top' is opened r/w. + * + * 1) This will convert the following chain: + * + * ... <- base <- ... <- top <- overlay <-... <- active * - * Requires that the overlay to 'top' is opened r/w, so that the backing file - * information in 'bs' can be properly updated. + * to + * + * ... <- base <- overlay <- active + * + * 2) It is allowed for bottom==base, in which case it converts: * - * E.g., this will convert the following chain: - * bottom <- base <- intermediate <- top <- active + * base <- ... <- top <- overlay <- ... <- active * * to * - * bottom <- base <- active + * base <- overlay <- active * - * It is allowed for bottom==base, in which case it converts: + * 2) It also allows active==top, in which case it converts: * - * base <- intermediate <- top <- active + * ... <- base <- ... <- top (active) * * to * - * base <- active + * ... <- base == active == top + * + * i.e. only base and lower remains: *top == *base when return. + * + * 3) If base==NULL, it will drop all the BDS below overlay and set its + * backing_hd to NULL. I.e.: * - * Error conditions: - * if active == top, that is considered an error + * base(NULL) <- ... <- overlay <- ... <- active + * + * to + * + * overlay <- ... <- active * */ int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top, BlockDriverState *base) { - BlockDriverState *intermediate; - BlockDriverState *base_bs = NULL; - BlockDriverState *new_top_bs = NULL; - BlkIntermediateStates *intermediate_state, *next; - int ret = -EIO; - - QSIMPLEQ_HEAD(states_to_delete, BlkIntermediateStates) states_to_delete; - QSIMPLEQ_INIT(&states_to_delete); + BlockDriverState *drop_start, *overlay, *bs; + int ret = -EINVAL; - if (!top->drv || !base->drv) { + assert(active); + assert(top); + /* Verify that top is in backing chain of active */ + bs = active; + while (bs && bs != top) { + bs = bs->backing_hd; + } + if (!bs) { goto exit; } + /* Verify that base is in backing chain of top */ + if (base) { + while (bs && bs != base) { + bs = bs->backing_hd; + } + if (bs != base) { + goto exit; + } + } - new_top_bs = bdrv_find_overlay(active, top); - - if (new_top_bs == NULL) { - /* we could not find the image above 'top', this is an error */ + if (!top->drv || (base && !base->drv)) { goto exit; } - - /* special case of new_top_bs->backing_hd already pointing to base - nothing - * to do, no intermediate images */ - if (new_top_bs->backing_hd == base) { + if (top == base) { + ret = 0; + goto exit; + } else if (top == active) { + assert(base); + drop_start = active->backing_hd; + bdrv_swap(active, base); + base->backing_hd = NULL; + bdrv_unref(drop_start); ret = 0; goto exit; } - intermediate = top; - - /* now we will go down through the list, and add each BDS we find - * into our deletion queue, until we hit the 'base' - */ - while (intermediate) { - intermediate_state = g_malloc0(sizeof(BlkIntermediateStates)); - intermediate_state->bs = intermediate; - QSIMPLEQ_INSERT_TAIL(&states_to_delete, intermediate_state, entry); - - if (intermediate->backing_hd == base) { - base_bs = intermediate->backing_hd; - break; - } - intermediate = intermediate->backing_hd; - } - if (base_bs == NULL) { - /* something went wrong, we did not end at the base. safely - * unravel everything, and exit with error */ + overlay = bdrv_find_overlay(active, top); + if (!overlay) { goto exit; } - - /* success - we can delete the intermediate states, and link top->base */ - ret = bdrv_change_backing_file(new_top_bs, base_bs->filename, - base_bs->drv ? base_bs->drv->format_name : ""); + ret = bdrv_change_backing_file(overlay, + base ? base->filename : NULL, + base ? base->drv->format_name : NULL); if (ret) { goto exit; } - new_top_bs->backing_hd = base_bs; - bdrv_refresh_limits(new_top_bs); - - QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) { - /* so that bdrv_close() does not recursively close the chain */ - intermediate_state->bs->backing_hd = NULL; - bdrv_unref(intermediate_state->bs); + bs = overlay->backing_hd; + bdrv_set_backing_hd(overlay, base); + if (base) { + bdrv_ref(base); + } + if (bs) { + bdrv_unref(bs); } ret = 0; - exit: - QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry, next) { - g_free(intermediate_state); - } return ret; } - static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset, size_t size) { diff --git a/block/commit.c b/block/commit.c index acec4ac..ac598d6 100644 --- a/block/commit.c +++ b/block/commit.c @@ -73,6 +73,7 @@ static void coroutine_fn commit_run(void *opaque) int bytes_written = 0; int64_t base_len; + overlay_bs = bdrv_find_overlay(active, top); ret = s->common.len = bdrv_getlength(top); @@ -154,7 +155,6 @@ exit_restore_reopen: if (s->base_flags != bdrv_get_flags(base)) { bdrv_reopen(base, s->base_flags, NULL); } - overlay_bs = bdrv_find_overlay(active, top); if (overlay_bs && s->orig_overlay_flags != bdrv_get_flags(overlay_bs)) { bdrv_reopen(overlay_bs, s->orig_overlay_flags, NULL); }