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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20250313233341.1675324-1-dhowells@redhat.com> <20250313233341.1675324-20-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 19/35] libceph, ceph: Convert users of ceph_pagelist 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: <2680946.1742336824.1@warthog.procyon.org.uk> Date: Tue, 18 Mar 2025 22:27:04 +0000 Message-ID: <2680947.1742336824@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Viacheslav Dubeyko wrote: > > /* > > - * number of encoded locks is stable, so copy to pagelist > > + * number of encoded locks is stable, so copy to databuf > > */ > > struct_len = 2 * sizeof(u32) + > > (num_fcntl_locks + num_flock_locks) * > > I think we have too many mysterious equations in CephFS code. :) That's not particularly a function of these patches. > > - err = ceph_pagelist_reserve(pagelist, > > - sizeof(u64) + sizeof(u32) + > > - pathlen + sizeof(rec.v1)); > > + err = ceph_databuf_reserve(dbuf, > > + sizeof(u64) + sizeof(u32) + > > + pathlen + sizeof(rec.v1), > > + GFP_NOFS); > > Yeah, another mysterious calculation. Why do we add sizeof(u64) and > sizeof(u32) here? Protocol element space. David