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Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <749dc130afd32accfd156b06f297585a56af47f3.camel@ibm.com> References: <749dc130afd32accfd156b06f297585a56af47f3.camel@ibm.com> <20250313233341.1675324-1-dhowells@redhat.com> <20250313233341.1675324-24-dhowells@redhat.com> To: Viacheslav Dubeyko , Ilya Dryomov Cc: dhowells@redhat.com, Alex Markuze , "slava@dubeyko.com" , "linux-block@vger.kernel.org" , "jlayton@kernel.org" , "linux-fsdevel@vger.kernel.org" , "ceph-devel@vger.kernel.org" , "dongsheng.yang@easystack.cn" , "linux-kernel@vger.kernel.org" Subject: Why use plain numbers and totals rather than predef'd constants for RPC sizes? Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3172945.1742482785.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Thu, 20 Mar 2025 14:59:45 +0000 Message-ID: <3172946.1742482785@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Viacheslav Dubeyko wrote: > > - dbuf =3D ceph_databuf_reply_alloc(1, 8 + sizeof(struct ceph_timespec= ), GFP_NOIO); > > - if (!dbuf) > > + request =3D ceph_databuf_reply_alloc(1, 8 + sizeof(struct ceph_times= pec), GFP_NOIO); > = > Ditto. Why do we have 8 + sizeof(struct ceph_timespec) here? Because that's the size of the composite protocol element. As to why it's using a total of plain integers and sizeofs rather than constant macros, Ilya is the person to ask according to git blame;-). I would probably prefer sizeof(__le64) here over 8, but I didn't want to change it too far from the existing code. If you want macro constants for these sorts of things, someone else who kn= ows the protocol better needs to do that. You could probably write something = to generate them (akin to rpcgen). David