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Wed, 21 Sep 2022 04:45:13 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.163]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8CA44492B06; Wed, 21 Sep 2022 04:45:13 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 6B46B21E6900; Wed, 21 Sep 2022 06:45:10 +0200 (CEST) From: Markus Armbruster To: Kevin Wolf Cc: Claudio Fontana , Richard Henderson , Paolo Bonzini , qemu-devel@nongnu.org, dinechin@redhat.com, Gerd Hoffmann , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Daniel P . =?utf-8?Q?Berrang=C3=A9?= , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v3 2/3] module: add Error arguments to module_load_one and module_load_qom_one References: <20220908145308.30282-1-cfontana@suse.de> <20220908145308.30282-3-cfontana@suse.de> <062faaa8-064c-f68a-e316-aaacb80efa5a@linaro.org> <3c6cb3ee-2470-654f-c2c4-3449861f9781@suse.de> <8682ad9f-aea8-0419-5ff6-c14493e4e980@suse.de> Date: Wed, 21 Sep 2022 06:45:10 +0200 In-Reply-To: (Kevin Wolf's message of "Tue, 20 Sep 2022 18:50:15 +0200") Message-ID: <87r105gwtl.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, 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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Kevin Wolf writes: > Am 08.09.2022 um 19:36 hat Claudio Fontana geschrieben: >> On 9/8/22 19:10, Claudio Fontana wrote: >> > On 9/8/22 18:03, Richard Henderson wrote: >> >> On 9/8/22 15:53, Claudio Fontana wrote: >> >>> @@ -446,8 +447,13 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags, >> >>> return -EINVAL; >> >>> } >> >>> >> >>> - block_module_load_one("dmg-bz2"); >> >>> - block_module_load_one("dmg-lzfse"); >> >>> + if (!block_module_load_one("dmg-bz2", &local_err) && local_err) { >> >>> + error_report_err(local_err); >> >>> + } >> >>> + local_err = NULL; >> >>> + if (!block_module_load_one("dmg-lzfse", &local_err) && local_err) { >> >>> + error_report_err(local_err); >> >>> + } >> >>> >> >>> s->n_chunks = 0; >> >>> s->offsets = s->lengths = s->sectors = s->sectorcounts = NULL; >> >> >> >> I wonder if these shouldn't fail hard if the modules don't exist? >> >> Or at least pass back the error. >> >> >> >> Kevin? >> >> is "dmg-bz" _required_ for dmg open to work? I suspect if the dmg >> image is not compressed, "dmg" can function even if the extra dmg-bz >> module is not loaded right? > > Indeed. The code seems to consider that the modules may not be present. > The behaviour in these cases is questionable (it seems to silently leave > the buffers as they are and return success), but the modules are clearly > optional. > >> I'd suspect we should then do: >> >> if (!block_module_load_one("dmg-bz2", &local_err)) { >> if (local_err) { >> error_report_err(local_err); >> return -EINVAL; >> } >> warn_report("dmg-bz2 is not present, dmg will skip bz2-compressed chunks */ >> } >> >> and same for dmg-lzfse...? > > Actually, I think during initialisation, we should just pass NULL as > errp and ignore any errors. > > When a request would access a block that can't be uncompressed because > of the missing module, that's where we can have a warn_report_once() and > arguably should fail the I/O request. Seems like asking for data corruption. To avoid it, the complete stack needs to handle I/O errors correctly. Can we detect presence of compressed blocks on open?