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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <20250806203705.2560493-1-dhowells@redhat.com> <2938703.1754673937@warthog.procyon.org.uk> To: Enzo Matsumiya Cc: dhowells@redhat.com, Steve French , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Wang Zhaolong , Stefan Metzmacher , Mina Almasry , linux-cifs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 00/31] netfs: [WIP] Allow the use of MSG_SPLICE_PAGES and use netmem allocator 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: <2942077.1754685186.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Fri, 08 Aug 2025 21:33:06 +0100 Message-ID: <2942078.1754685186@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Enzo Matsumiya wrote: > Anyway, if you want me to test, just send me the patches. > I have your linux-fs remote as well, if that's easier. If you look at: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/= ?h=3Dcifs-experimental You can see a patch with the subject "cifs: [!] FIX transport compression"= . Grab that and everything up to it. I'm pretty certain it won't work, but I can't test it. Well, maybe I can force it on and look at the packet trace if wireshark can handle it. Some things to note: (1) In smb_compress(), netfs_alloc_bvecq_buffer() is used to allocate the destination buffer and attach it to a bvecq, which it also allocates.= An iterator can be set on this to define part of the buffer to operate o= n. (2) vmap_bvecq() is used to map the source and the destination buffers. = It extracts the pages and then calls vmap() on them. (3) Space for the compression header is allocated by smb_send_rqst() in t= he first bvecq slot along with the rfc1002 header and transform header (= if sealing). A pointer is passed down to smb_compress(). (4) It attempts to adjust the values such that the compression header is included in the encrypted section if also sealing. However, it might= be better to have smb_compress() place it in the output buffer. (5) If compression is successful, smb_compress() switches the original bv= ecq and the output bvecq and moves the header segment from the original t= o the output. (6) If the compression algo returns -EMSGSIZE, then the compression heade= r is excluded from the header segment. David