From: David Laight <David.Laight@ACULAB.COM>
To: 'David Howells' <dhowells@redhat.com>
Cc: Steve French <smfrench@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Shyam Prasad N <nspmangalore@gmail.com>,
Rohith Surabattula <rohiths.msft@gmail.com>,
Tom Talpey <tom@talpey.com>, Stefan Metzmacher <metze@samba.org>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
Jeff Layton <jlayton@kernel.org>,
"linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Steve French <sfrench@samba.org>
Subject: RE: [RFC 08/13] cifs: Add a function to read into an iter from a socket
Date: Thu, 26 Jan 2023 16:09:05 +0000 [thread overview]
Message-ID: <5d0bc437eebb4d5aa4774962a4970095@AcuMS.aculab.com> (raw)
In-Reply-To: <2862713.1674747841@warthog.procyon.org.uk>
From: David Howells
> Sent: 26 January 2023 15:44
...
> > I'm also not 100% sure that taking a copy of an iov_iter is a good idea.
>
> It shouldn't matter as the only problematic iterator is ITER_PIPE (advancing
> that has side effects) - and splice_read is handled specially by patch 4. The
> problem with splice_read with the way cifs works is that it likes to subdivide
> its read/write requests across multiple reqs and then subsubdivide them if
> certain types of failure occur. But you can't do that with ITER_PIPE.
I was thinking that even if ok at the moment it might be troublesome later.
Somewhere I started writing a patch to put the iov_cache[] for user
requests into the same structure as the iterator.
Copying those might cause oddities.
> I build an ITER_BVEC from ITER_PIPE, ITER_UBUF and ITER_IOVEC in the top
> levels with pins inserted as appropriate and hand the ITER_BVEC down. For
> user-backed iterators it has to be done this way because the I/O may get
> shuffled off to a different thread.
For sub-page sided transfers it is probably worth doing a bounce buffer
copy of user requests - just to save all the complex page pinning code.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-01-26 16:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 21:45 [RFC 00/13] smb3: Use iov_iters down to the network transport and fix DIO page pinning David Howells
2023-01-25 21:45 ` [RFC 01/13] netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator David Howells
2023-01-25 21:45 ` [RFC 02/13] netfs: Add a function to extract an iterator into a scatterlist David Howells
2023-01-25 21:45 ` [RFC 03/13] cifs: Fix oops due to uncleared server->smbd_conn in reconnect David Howells
2023-01-25 21:45 ` [RFC 04/13] cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE David Howells
2023-01-25 21:45 ` [RFC 05/13] cifs: Add a function to build an RDMA SGE list from an iterator David Howells
2023-01-25 21:45 ` [RFC 06/13] cifs: Add a function to Hash the contents of " David Howells
2023-01-27 10:27 ` Herbert Xu
2023-01-27 10:33 ` David Howells
2023-01-27 10:38 ` Herbert Xu
2023-01-25 21:45 ` [RFC 07/13] cifs: Add some helper functions David Howells
2023-01-25 21:45 ` [RFC 08/13] cifs: Add a function to read into an iter from a socket David Howells
2023-01-26 9:27 ` David Laight
2023-01-26 15:44 ` David Howells
2023-01-26 16:09 ` David Laight [this message]
2023-01-26 16:41 ` David Howells
2023-01-25 21:45 ` [RFC 09/13] cifs: Change the I/O paths to use an iterator rather than a page list David Howells
2023-01-25 21:45 ` [RFC 10/13] cifs: Build the RDMA SGE list directly from an iterator David Howells
2023-01-25 21:45 ` [RFC 11/13] cifs: Remove unused code David Howells
2023-01-25 21:45 ` [RFC 12/13] cifs: Fix problem with encrypted RDMA data read David Howells
2023-01-25 21:45 ` [RFC 13/13] cifs: DIO to/from KVEC-type iterators should now work David Howells
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