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Mon, 27 May 2024 10:41:43 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D231A200A381; Mon, 27 May 2024 10:41:42 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id BF5E921E6757; Mon, 27 May 2024 12:41:41 +0200 (CEST) From: Markus Armbruster To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: qemu-devel@nongnu.org, fam@euphon.net, kwolf@redhat.com, hreitz@redhat.com, marcandre.lureau@redhat.com, peterx@redhat.com, farosas@suse.de, pbonzini@redhat.com, richard.henderson@linaro.org, qemu-block@nongnu.org Subject: Re: [PATCH 4/6] cpus: Improve error messages on memsave, pmemsave write error In-Reply-To: ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Mon, 13 May 2024 16:58:11 +0200") References: <20240513141703.549874-1-armbru@redhat.com> <20240513141703.549874-5-armbru@redhat.com> <5ad42c0c-abd0-4fce-8204-9effa4765ab8@linaro.org> <87r0e56a8p.fsf@pond.sub.org> Date: Mon, 27 May 2024 12:41:41 +0200 Message-ID: <871q5nedui.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 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: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.145, 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_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org Philippe Mathieu-Daud=C3=A9 writes: > On 13/5/24 16:45, Markus Armbruster wrote: >> Philippe Mathieu-Daud=C3=A9 writes: >>=20 >>> On 13/5/24 16:17, Markus Armbruster wrote: >>>> qmp_memsave() and qmp_pmemsave() report fwrite() error as >>>> >>>> An IO error has occurred >>>> >>>> Improve this to >>>> >>>> writing memory to '' failed >>>> >>>> Signed-off-by: Markus Armbruster >>>> --- >>>> system/cpus.c | 6 ++++-- >>>> 1 file changed, 4 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/system/cpus.c b/system/cpus.c >>>> index 68d161d96b..f8fa78f33d 100644 >>>> --- a/system/cpus.c >>>> +++ b/system/cpus.c >>>> @@ -813,7 +813,8 @@ void qmp_memsave(int64_t addr, int64_t size, const= char *filename, >>>> goto exit; >>>> } >>>> if (fwrite(buf, 1, l, f) !=3D l) { >>>> - error_setg(errp, QERR_IO_ERROR); >>>> + error_setg(errp, "writing memory to '%s' failed", >>>> + filename); >>>> goto exit; >>>> } >>>> addr +=3D l; >>>> @@ -843,7 +844,8 @@ void qmp_pmemsave(int64_t addr, int64_t size, cons= t char *filename, >>>> l =3D size; >>>> cpu_physical_memory_read(addr, buf, l); >>>> if (fwrite(buf, 1, l, f) !=3D l) { >>>> - error_setg(errp, QERR_IO_ERROR); >>>> + error_setg(errp, "writing memory to '%s' failed", >>>> + filename); >>> >>> What about including errno with error_setg_errno()? >> >> Sure fwrite() fails with errno reliably set? The manual page doesn't >> mention it... > > Indeed. I can see some uses in the code base: > > qemu-io-cmds.c:409: if (ferror(f)) { > qemu-io-cmds.c-410- perror(file_name); This is after fread(), which isn't specified to set errno, either. > qga/commands-posix.c-632- write_count =3D fwrite(buf, 1, count, fh); > qga/commands-posix.c:633: if (ferror(fh)) { > qga/commands-posix.c-634- error_setg_errno(errp, errno, "failed to= write to file"); This one is after fwrite(), like the code I'm changing. > util/qemu-config.c:152: if (ferror(fp)) { > util/qemu-config.c-153- loc_pop(&loc); > util/qemu-config.c-154- error_setg_errno(errp, errno, "Cannot read= config file"); This is after fgets(), which isn't specified to set errno, either. All three uses feel iffy to me. They work if the stream's error indicator is clear before fread() / fwrite() / fgets(), and it is set there, and the reason for it being set is something that sets errno (such as a failed system call, which seems likely), and errno remains untouched until after ferror(). Too much "if", "seems likely" for my taste. > Regardless, > > Reviewed-by: Philippe Mathieu-Daud=C3=A9 Thanks!