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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58760 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9qGk-00024Z-7J for qemu-devel@archiver.kernel.org; Wed, 10 Feb 2021 09:15:02 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37524) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9qFk-0001QI-LI for qemu-devel@nongnu.org; Wed, 10 Feb 2021 09:14:00 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:37551) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9qFi-0003B8-VO for qemu-devel@nongnu.org; Wed, 10 Feb 2021 09:14:00 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612966437; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=t+3FvZtDceuylzhsnQQhaMcF9rKQ9MXFZBNz6oshfUo=; b=iaqpISuUVqmPUqIJZQLarMGmQ7BOm45JQiwtp4CbMAPP74PVuKUhbvQBiMt6mCGi914LI3 HlqeChEEwmY4bnqIHe2ReSrXLw/QSPTNdVuSMOEMeroaAXx4lVEaH6l2Cl/El37LiC4wF+ WgisB3ajjOXzYKf/kOClXzf94YCTr+s= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-304-mNtCmSocNkOIc2_3d2sWTw-1; Wed, 10 Feb 2021 09:13:53 -0500 X-MC-Unique: mNtCmSocNkOIc2_3d2sWTw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B3307801976; Wed, 10 Feb 2021 14:13:51 +0000 (UTC) Received: from merkur.fritz.box (ovpn-115-33.ams2.redhat.com [10.36.115.33]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2F0985D75A; Wed, 10 Feb 2021 14:13:50 +0000 (UTC) Date: Wed, 10 Feb 2021 15:13:48 +0100 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v2 30/36] block: bdrv_reopen_multiple: refresh permissions on updated graph Message-ID: <20210210141348.GD5144@merkur.fritz.box> References: <20201127144522.29991-1-vsementsov@virtuozzo.com> <20201127144522.29991-31-vsementsov@virtuozzo.com> <20210205175706.GI7072@merkur.fritz.box> <88b2a88e-e5dd-9ce6-a11c-20ba2c4befa9@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <88b2a88e-e5dd-9ce6-a11c-20ba2c4befa9@virtuozzo.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-block@nongnu.org, armbru@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, den@openvz.org, jsnow@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 08.02.2021 um 12:21 hat Vladimir Sementsov-Ogievskiy geschrieben: > 05.02.2021 20:57, Kevin Wolf wrote: > > Am 27.11.2020 um 15:45 hat Vladimir Sementsov-Ogievskiy geschrieben: > > > Move bdrv_reopen_multiple to new paradigm of permission update: > > > first update graph relations, then do refresh the permissions. > > > > > > We have to modify reopen process in file-posix driver: with new scheme > > > we don't have prepared permissions in raw_reopen_prepare(), so we > > > should reconfigure fd in raw_check_perm(). Still this seems more native > > > and simple anyway. > > > > Hm... The diffstat shows that it is simpler because it needs less code. > > > > But relying on the permission change callbacks for getting a new file > > descriptor that changes more than just permissions doesn't feel > > completely right either. Can we even expect the permission callbacks to > > be called when the permissions aren't changed? > > With new scheme permission update becomes an obvious step of > bdrv_reopen_multiple(): we do call bdrv_list_refresh_perms(), for the > list of all touched nodes and all their subtrees. And callbacks are > called unconditionally bdrv_node_refresh_perm()->bdrv_drv_set_perm(). > So, I think, we can rely on it. Probably worth one-two comments. Yes, some comments in the right places that we must call the driver callbacks even if the permissions are the same as before wouldn't hurt. > > > > But then, reopen and permission updates were already a bit entangled > > before. If we can guarantee that the permission functions will always be > > called, even if the permissions don't change, I guess it's okay. > > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy > > > --- > > > include/block/block.h | 2 +- > > > block.c | 183 +++++++++++------------------------------- > > > block/file-posix.c | 84 +++++-------------- > > > 3 files changed, 70 insertions(+), 199 deletions(-) > > > > > > diff --git a/include/block/block.h b/include/block/block.h > > > index 0f21ef313f..82271d9ccd 100644 > > > --- a/include/block/block.h > > > +++ b/include/block/block.h > > > @@ -195,7 +195,7 @@ typedef struct BDRVReopenState { > > > BlockdevDetectZeroesOptions detect_zeroes; > > > bool backing_missing; > > > bool replace_backing_bs; /* new_backing_bs is ignored if this is false */ > > > - BlockDriverState *new_backing_bs; /* If NULL then detach the current bs */ > > > + BlockDriverState *old_backing_bs; /* keep pointer for permissions update */ > > > uint64_t perm, shared_perm; > > > > perm and shared_perm are unused now and can be removed. > > > > > QDict *options; > > > QDict *explicit_options; > > > diff --git a/block.c b/block.c > > > index 617cba9547..474e624152 100644 > > > --- a/block.c > > > +++ b/block.c > > > @@ -103,8 +103,9 @@ static int bdrv_attach_child_common(BlockDriverState *child_bs, > > > GSList **tran, Error **errp); > > > static void bdrv_remove_backing(BlockDriverState *bs, GSList **tran); > > > -static int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue > > > - *queue, Error **errp); > > > +static int bdrv_reopen_prepare(BDRVReopenState *reopen_state, > > > + BlockReopenQueue *queue, > > > + GSList **set_backings_tran, Error **errp); > > > static void bdrv_reopen_commit(BDRVReopenState *reopen_state); > > > static void bdrv_reopen_abort(BDRVReopenState *reopen_state); > > > @@ -2403,6 +2404,7 @@ static void bdrv_list_abort_perm_update(GSList *list) > > > } > > > } > > > +__attribute__((unused)) > > > static void bdrv_abort_perm_update(BlockDriverState *bs) > > > { > > > g_autoptr(GSList) list = bdrv_topological_dfs(NULL, NULL, bs); > > > @@ -2498,6 +2500,7 @@ char *bdrv_perm_names(uint64_t perm) > > > * > > > * Needs to be followed by a call to either bdrv_set_perm() or > > > * bdrv_abort_perm_update(). */ > > > +__attribute__((unused)) > > > static int bdrv_check_update_perm(BlockDriverState *bs, BlockReopenQueue *q, > > > uint64_t new_used_perm, > > > uint64_t new_shared_perm, > > > @@ -4100,10 +4103,6 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue, > > > bs_entry->state.explicit_options = explicit_options; > > > bs_entry->state.flags = flags; > > > - /* This needs to be overwritten in bdrv_reopen_prepare() */ > > > - bs_entry->state.perm = UINT64_MAX; > > > - bs_entry->state.shared_perm = 0; > > > - > > > /* > > > * If keep_old_opts is false then it means that unspecified > > > * options must be reset to their original value. We don't allow > > > @@ -4186,40 +4185,37 @@ BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue, > > > */ > > > int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp) > > > { > > > - int ret = -1; > > > + int ret = 0; > > > > I would prefer to leave this right before the 'goto cleanup'. > > > > Not sure if I fully understand all consequences yet, but overall, apart > > from my concerns about file-posix and the potential AioContext locking > > problems, this looks like a nice simplification of the process. > > > > Come to think of it, the AioContext handling is probably wrong already > > before your series. reopen_commit for one node could move the whole tree > > to a different context and then the later nodes would all be processed > > while holding the wrong lock. > > > > Probably proper way is to acquire all involved aio contexts as I do in > 29 and update aio-context updating functions to work in such > conditions(all aio contexts are already acquired by caller). Well, as we already discussed, patch 29 is probably wrong in its current form. But you seemed to have a solution in mind, which will hopefully work here, too. Kevin