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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20260304140328.112636-1-dhowells@redhat.com> <20260304140328.112636-3-dhowells@redhat.com> To: Christoph Hellwig Cc: dhowells@redhat.com, Matthew Wilcox , Jens Axboe , Leon Romanovsky , Christian Brauner , Paulo Alcantara , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Paulo Alcantara , Steve French , Namjae Jeon , Tom Talpey , Chuck Lever Subject: Re: [RFC PATCH 02/17] vfs: Implement a FIEMAP callback Precedence: bulk X-Mailing-List: netfs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Wed, 04 Mar 2026 14:21:54 +0000 Message-ID: <114166.1772634114@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: a4KHc-ZkqbO4IRTKUeGsOUR-y8iM8d2X-LxbteYFe50_1772634121 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-ID: <114165.1772634114.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Christoph Hellwig wrote: > On Wed, Mar 04, 2026 at 02:03:09PM +0000, David Howells wrote: > > Implement a callback in the internal kernel FIEMAP API so that kernel u= sers > > can make use of it as the filler function expects to write to userspace= . > > This allows the FIEMAP data to be captured and parsed. This is useful = for > > cachefiles and also potentially for knfsd and ksmbd to implement their > > equivalents of FIEMAP remotely rather than using SEEK_DATA/SEEK_HOLE. >=20 > Hell no. FIEMAP is purely a debugging toool and must not get anywhere > near a data path. NAK to all of this. So I have to stick with SEEK_DATA/SEEK_HOLE for this? (Before you ask, yes, I do want to keep track of this myself, but working o= ut the best way to do that without reinventing the filesystem is the issue - well, that and finding time to do it). David