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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <4413c4ed03696b76ccd7903a87bd4c72ad9c883e.camel@ibm.com> References: <4413c4ed03696b76ccd7903a87bd4c72ad9c883e.camel@ibm.com> <20250313233341.1675324-1-dhowells@redhat.com> <20250313233341.1675324-19-dhowells@redhat.com> To: Viacheslav Dubeyko Cc: dhowells@redhat.com, Alex Markuze , "slava@dubeyko.com" , "linux-block@vger.kernel.org" , "idryomov@gmail.com" , "jlayton@kernel.org" , "linux-fsdevel@vger.kernel.org" , "ceph-devel@vger.kernel.org" , "dongsheng.yang@easystack.cn" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 18/35] libceph, rbd: Convert some page arrays to ceph_databuf 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: <2680899.1742336740.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Tue, 18 Mar 2025 22:25:40 +0000 Message-ID: <2680900.1742336740@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Viacheslav Dubeyko wrote: > > /* > > * The response data for a STAT call consists of: > > @@ -2118,14 +2118,12 @@ static int rbd_osd_setup_stat(struct ceph_osd_= request *osd_req, int which) > > * le32 tv_nsec; > > * } mtime; > > */ > > - pages =3D ceph_alloc_page_vector(1, GFP_NOIO); > > - if (IS_ERR(pages)) > > - return PTR_ERR(pages); > > + dbuf =3D ceph_databuf_reply_alloc(1, 8 + sizeof(struct ceph_timespec= ), GFP_NOIO); > = > What this 8 + sizeof(struct ceph_timespec) means? Why do we use 8 here? = :) See the comment that's partially obscured by the patch hunk line: /* * The response data for a STAT call consists of: * le64 length; * struct { * le32 tv_sec; * le32 tv_nsec; * } mtime; */ If you want to clean up and formalise all of these sorts of things, you mi= ght need to invest in an rpcgen-like tool. I've occasionally toyed with the i= dea for afs in the kernel (I've hand-written all the marshalling/unmarshalling code in fs/afs/fsclient.c, fs/afs/yfsclient.c and fs/afs/vlclient.c, but t= here are some not-so-simple RPC calls to handle - FetchData and StoreData for example). David