From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 51594C3ABD8 for ; Wed, 14 May 2025 16:53:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uFFLq-0001LY-E0; Wed, 14 May 2025 12:53:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uFFLo-0001Gn-US for qemu-devel@nongnu.org; Wed, 14 May 2025 12:53:00 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uFFLn-0005zU-Ey for qemu-devel@nongnu.org; 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Wed, 14 May 2025 16:52:50 +0000 (UTC) Received: from redhat.com (unknown [10.44.33.207]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0E03730001A1; Wed, 14 May 2025 16:52:46 +0000 (UTC) Date: Wed, 14 May 2025 18:52:44 +0200 From: Kevin Wolf To: Fiona Ebner Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, den@virtuozzo.com, andrey.drobyshev@virtuozzo.com, hreitz@redhat.com, stefanha@redhat.com, eblake@redhat.com, jsnow@redhat.com, vsementsov@yandex-team.ru Subject: Re: [PATCH 03/11] block/snapshot: move drain outside of read-locked bdrv_snapshot_delete() Message-ID: References: <20250508140936.3344485-1-f.ebner@proxmox.com> <20250508140936.3344485-4-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250508140936.3344485-4-f.ebner@proxmox.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -37 X-Spam_score: -3.8 X-Spam_bar: --- X-Spam_report: (-3.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.686, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 08.05.2025 um 16:09 hat Fiona Ebner geschrieben: > This is in preparation to mark bdrv_drained_begin() as GRAPH_UNLOCKED. > > More granular draining is not trivially possible, because > bdrv_snapshot_delete() can recursively call itself. > > Signed-off-by: Fiona Ebner > --- > block/snapshot.c | 18 ++++++++++++------ > blockdev.c | 25 +++++++++++++++++-------- > qemu-img.c | 2 ++ > 3 files changed, 31 insertions(+), 14 deletions(-) > > diff --git a/block/snapshot.c b/block/snapshot.c > index 22567f1fb9..7788e1130b 100644 > --- a/block/snapshot.c > +++ b/block/snapshot.c > @@ -327,7 +327,7 @@ int bdrv_snapshot_goto(BlockDriverState *bs, > > /** > * Delete an internal snapshot by @snapshot_id and @name. > - * @bs: block device used in the operation > + * @bs: block device used in the operation, needs to be drained Forgot to add this piece of nitpicking on the previous patch: Other places say "must be drained", which I slightly prefer because of how RFC 2119 has "MUST", but not "NEEDS TO". Matter of taste, I guess, but if you agree, we could change it for the non-RFC series. > * @snapshot_id: unique snapshot ID, or NULL > * @name: snapshot name, or NULL > * @errp: location to store error > @@ -356,6 +356,8 @@ int bdrv_snapshot_delete(BlockDriverState *bs, > BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs); > int ret; > > + assert(qatomic_read(&bs->quiesce_counter) > 0); > + > GLOBAL_STATE_CODE(); > > if (!drv) { > @@ -368,9 +370,6 @@ int bdrv_snapshot_delete(BlockDriverState *bs, > return -EINVAL; > } > > - /* drain all pending i/o before deleting snapshot */ > - bdrv_drained_begin(bs); > - > if (drv->bdrv_snapshot_delete) { > ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp); > } else if (fallback_bs) { > @@ -382,7 +381,6 @@ int bdrv_snapshot_delete(BlockDriverState *bs, > ret = -ENOTSUP; > } > > - bdrv_drained_end(bs); > return ret; > } > > @@ -573,9 +571,13 @@ int bdrv_all_delete_snapshot(const char *name, > GList *iterbdrvs; > > GLOBAL_STATE_CODE(); > - GRAPH_RDLOCK_GUARD_MAINLOOP(); > + > + bdrv_drain_all_begin(); > + bdrv_graph_rdlock_main_loop(); > > if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) { > + bdrv_graph_rdunlock_main_loop(); > + bdrv_drain_all_end(); > return -1; > } I think this wants to be changed into: ret = bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp); if (ret < 0) { goto out; } (Changing the return value from -1 to -errno is fine for the callers.) > @@ -594,12 +596,16 @@ int bdrv_all_delete_snapshot(const char *name, > if (ret < 0) { > error_prepend(errp, "Could not delete snapshot '%s' on '%s': ", > name, bdrv_get_device_or_node_name(bs)); > + bdrv_graph_rdunlock_main_loop(); > + bdrv_drain_all_end(); > return -1; > } Same here. > > iterbdrvs = iterbdrvs->next; > } > > + bdrv_graph_rdunlock_main_loop(); > + bdrv_drain_all_end(); > return 0; > } Kevin