From patchwork Mon Mar 11 16:50:11 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Wolf X-Patchwork-Id: 1054603 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=redhat.com Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 44J47P3TVyz9s55 for ; Tue, 12 Mar 2019 03:58:39 +1100 (AEDT) Received: from localhost ([127.0.0.1]:36810 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h3OG4-0000JT-Ga for incoming@patchwork.ozlabs.org; Mon, 11 Mar 2019 12:58:36 -0400 Received: from eggs.gnu.org ([209.51.188.92]:59362) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h3O9V-0003FI-VB for qemu-devel@nongnu.org; Mon, 11 Mar 2019 12:51:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h3O8G-0007dg-6e for qemu-devel@nongnu.org; Mon, 11 Mar 2019 12:50:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43914) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1h3O8E-0007bC-T9; Mon, 11 Mar 2019 12:50:31 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 24EA7307E049; Mon, 11 Mar 2019 16:50:30 +0000 (UTC) Received: from localhost.localdomain.com (ovpn-116-234.ams2.redhat.com [10.36.116.234]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7FEFD600CD; Mon, 11 Mar 2019 16:50:28 +0000 (UTC) From: Kevin Wolf To: qemu-block@nongnu.org Date: Mon, 11 Mar 2019 17:50:11 +0100 Message-Id: <20190311165017.32247-5-kwolf@redhat.com> In-Reply-To: <20190311165017.32247-1-kwolf@redhat.com> References: <20190311165017.32247-1-kwolf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Mon, 11 Mar 2019 16:50:30 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2 04/10] block: Make permission changes in reopen less wrong X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, pkrempa@redhat.com, berto@igalia.com, qemu-devel@nongnu.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The way that reopen interacts with permission changes has one big problem: Both operations are recursive, and the permissions are changes for each node in the reopen queue. For a simple graph that consists just of parent and child, .bdrv_check_perm will be called twice for the child, once recursively when adjusting the permissions of parent, and once again when the child itself is reopened. Even worse, the first .bdrv_check_perm call happens before .bdrv_reopen_prepare was called for the child and the second one is called afterwards. Making sure that .bdrv_check_perm (and the other permission callbacks) are called only once is hard. We can cope with multiple calls right now, but as soon as file-posix gets a dynamic auto-read-only that may need to open a new file descriptor, we get the additional requirement that all of them are after the .bdrv_reopen_prepare call. So reorder things in bdrv_reopen_multiple() to first call .bdrv_reopen_prepare for all involved nodes and only then adjust permissions. Signed-off-by: Kevin Wolf --- block.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-) diff --git a/block.c b/block.c index e18bd5eefd..9b9d25e843 100644 --- a/block.c +++ b/block.c @@ -1698,6 +1698,7 @@ static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared); typedef struct BlockReopenQueueEntry { bool prepared; + bool perms_checked; BDRVReopenState state; QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry; } BlockReopenQueueEntry; @@ -3166,6 +3167,16 @@ int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **er bs_entry->prepared = true; } + QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) { + BDRVReopenState *state = &bs_entry->state; + ret = bdrv_check_perm(state->bs, bs_queue, state->perm, + state->shared_perm, NULL, errp); + if (ret < 0) { + goto cleanup_perm; + } + bs_entry->perms_checked = true; + } + /* If we reach this point, we have success and just need to apply the * changes */ @@ -3174,7 +3185,20 @@ int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **er } ret = 0; +cleanup_perm: + QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) { + BDRVReopenState *state = &bs_entry->state; + + if (!bs_entry->perms_checked) { + continue; + } + if (ret == 0) { + bdrv_set_perm(state->bs, state->perm, state->shared_perm); + } else { + bdrv_abort_perm_update(state->bs); + } + } cleanup: QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) { if (ret) { @@ -3428,12 +3452,6 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, } while ((entry = qdict_next(reopen_state->options, entry))); } - ret = bdrv_check_perm(reopen_state->bs, queue, reopen_state->perm, - reopen_state->shared_perm, NULL, errp); - if (ret < 0) { - goto error; - } - ret = 0; /* Restore the original reopen_state->options QDict */ @@ -3500,9 +3518,6 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) bdrv_refresh_limits(bs, NULL); - bdrv_set_perm(reopen_state->bs, reopen_state->perm, - reopen_state->shared_perm); - new_can_write = !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE); if (!old_can_write && new_can_write && drv->bdrv_reopen_bitmaps_rw) { @@ -3534,8 +3549,6 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state) if (drv->bdrv_reopen_abort) { drv->bdrv_reopen_abort(reopen_state); } - - bdrv_abort_perm_update(reopen_state->bs); }