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([2a02:8071:5055:3f20:7ad9:a400:6d51:83e6]) by smtp.gmail.com with ESMTPSA id j17sm6723435wmq.41.2021.12.16.06.57.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Dec 2021 06:57:33 -0800 (PST) Message-ID: Date: Thu, 16 Dec 2021 15:57:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v5 10/31] block.c: modify .attach and .detach callbacks of child_of_bds To: Emanuele Giuseppe Esposito , qemu-block@nongnu.org References: <20211124064418.3120601-1-eesposit@redhat.com> <20211124064418.3120601-11-eesposit@redhat.com> From: Hanna Reitz In-Reply-To: <20211124064418.3120601-11-eesposit@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=hreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.718, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.034, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: , Cc: Kevin Wolf , Fam Zheng , Vladimir Sementsov-Ogievskiy , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Eduardo Habkost , Juan Quintela , qemu-devel@nongnu.org, John Snow , Richard Henderson , Markus Armbruster , "Dr. David Alan Gilbert" , Stefan Hajnoczi , Paolo Bonzini , Eric Blake Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 24.11.21 07:43, Emanuele Giuseppe Esposito wrote: > According to the assertions put in the previous patch, we should > first drain and then modify the ->children list. In this way > we prevent other iothreads to read the list while it is being > updated. > > In this case, moving the drain won't cause any harm, because > child is a parameter of the drain function so it will still be > included in the operation, despite not being in the list. Sounds good. > Signed-off-by: Emanuele Giuseppe Esposito > --- > block.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/block.c b/block.c > index 522a273140..5516c84ec4 100644 > --- a/block.c > +++ b/block.c > @@ -1416,6 +1416,7 @@ static void bdrv_child_cb_attach(BdrvChild *child) > { > BlockDriverState *bs = child->opaque; > > + bdrv_apply_subtree_drain(child, bs); > assert_bdrv_graph_writable(bs); > QLIST_INSERT_HEAD(&bs->children, child, next); > > @@ -1423,7 +1424,6 @@ static void bdrv_child_cb_attach(BdrvChild *child) > bdrv_backing_attach(child); > } > > - bdrv_apply_subtree_drain(child, bs); I think we should also remove the empty line above. Hanna > } > > static void bdrv_child_cb_detach(BdrvChild *child) > @@ -1434,10 +1434,9 @@ static void bdrv_child_cb_detach(BdrvChild *child) > bdrv_backing_detach(child); > } > > - bdrv_unapply_subtree_drain(child, bs); > - > assert_bdrv_graph_writable(bs); > QLIST_REMOVE(child, next); > + bdrv_unapply_subtree_drain(child, bs); > } > > static int bdrv_child_cb_update_filename(BdrvChild *c, BlockDriverState *base,