From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Amir Goldstein <amir73il@gmail.com>,
Steve French <smfrench@gmail.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Luis Henriques <lhenriques@suse.de>,
Trond Myklebust <trondmy@hammerspace.com>,
"samba-technical@lists.samba.org"
<samba-technical@lists.samba.org>,
"drinkcat@chromium.org" <drinkcat@chromium.org>,
"iant@google.com" <iant@google.com>,
"linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
"darrick.wong@oracle.com" <darrick.wong@oracle.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"jlayton@kernel.org" <jlayton@kernel.org>,
"llozano@chromium.org" <llozano@chromium.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
"miklos@szeredi.hu" <miklos@szeredi.hu>,
"viro@zeniv.linux.org.uk" <viro@zeniv.linux.org.uk>,
"dchinner@redhat.com" <dchinner@redhat.com>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"sfrench@samba.org" <sfrench@samba.org>,
"ceph-devel@vger.kernel.org" <ceph-devel@vger.kernel.org>
Subject: Re: [PATCH v2] vfs: prevent copy_file_range to copy across devices
Date: Thu, 18 Feb 2021 08:34:49 +0100 [thread overview]
Message-ID: <YC4YmTWtIgeyjZ6h@kroah.com> (raw)
In-Reply-To: <216103D5-0575-4BFC-9802-2C21A1B12DF9@dilger.ca>
On Wed, Feb 17, 2021 at 05:50:35PM -0700, Andreas Dilger wrote:
> On Feb 17, 2021, at 1:08 AM, Amir Goldstein <amir73il@gmail.com> wrote:
> >
> > You are missing my point.
> > Never mind which server. The server does not *need* to rely on
> > vfs_copy_file_range() to copy files from XFS to ext4.
> > The server is very capable of implementing the fallback generic copy
> > in case source/target fs do not support native {copy,remap}_file_range().
> >
> > w.r.t semantics of copy_file_range() syscall vs. the fallback to userespace
> > 'cp' tool (check source file size before copy or not), please note that the
> > semantics of CIFS_IOC_COPYCHUNK_FILE are that of the former:
> >
> > rc = cifs_file_copychunk_range(xid, src_file.file, 0, dst_file, 0,
> > src_inode->i_size, 0);
> >
> > It will copy zero bytes if advertised source file size if zero.
> >
> > NFS server side copy semantics are currently de-facto the same
> > because both the client and the server will have to pass through this
> > line in vfs_copy_file_range():
> >
> > if (len == 0)
> > return 0;
> >
> > IMO, and this opinion was voiced by several other filesystem developers,
> > the shortend copy semantics are the correct semantics for copy_file_range()
> > syscall as well as for vfs_copy_file_range() for internal kernel users.
> >
> > I guess what this means is that if the 'cp' tool ever tries an opportunistic
> > copy_file_range() syscall (e.g. --cfr=auto), it may result in zero size copy.
>
> Having a syscall that does the "wrong thing" when called on two files
> doesn't make sense. Expecting userspace to check whether source/target
> files supports CFR is also not practical. This is trivial for the
> kernel to determine and return -EOPNOTSUPP to the caller if the source
> file (procfs/sysfs/etc) does not work with CFR properly.
How does the kernel "know" that a specific file in a specific filesystem
will not work with CFR "properly"? That goes back to the original patch
which tried to label each and every filesystem type with a
"supported/not supported" type of flag, which was going to be a mess,
especially as it seems that this might be a file-specific thing, not a
filesystem-specific thing.
The goal of the patch _should_ be that the kernel figure it out itself,
but so far no one seems to be able to explain how that can be done :(
So, any hints?
thanks,
greg k-h
next prev parent reply other threads:[~2021-02-18 7:50 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAOQ4uxiFGjdvX2-zh5o46pn7RZhvbGHH0wpzLPuPOom91FwWeQ@mail.gmail.com>
2021-02-15 15:43 ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Luis Henriques
2021-02-15 16:02 ` Trond Myklebust
2021-02-16 0:25 ` Steve French
2021-02-15 16:34 ` Amir Goldstein
2021-02-15 16:53 ` Trond Myklebust
2021-02-15 17:24 ` Amir Goldstein
2021-02-15 18:57 ` Trond Myklebust
2021-02-15 19:43 ` Amir Goldstein
2021-02-16 11:17 ` Luis Henriques
2021-02-16 11:28 ` gregkh
2021-02-16 12:01 ` Luis Henriques
2021-02-16 12:08 ` Greg KH
2021-02-16 13:51 ` Amir Goldstein
2021-02-16 16:42 ` Luis Henriques
2021-02-16 17:44 ` Amir Goldstein
2021-02-16 18:55 ` Luis Henriques
2021-02-16 19:20 ` Amir Goldstein
2021-02-16 19:27 ` Anna Schumaker
2021-02-16 19:31 ` Steve French
2021-02-16 19:40 ` Amir Goldstein
2021-02-16 21:15 ` Steve French
2021-02-17 8:08 ` Amir Goldstein
2021-02-17 17:26 ` [PATCH v3] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-17 20:47 ` Amir Goldstein
2021-02-18 0:56 ` Nicolas Boichat
2021-02-18 5:32 ` Olga Kornievskaia
2021-02-18 6:47 ` Amir Goldstein
2021-02-18 16:28 ` Olga Kornievskaia
2021-02-18 7:43 ` Christoph Hellwig
2021-02-18 0:50 ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Andreas Dilger
2021-02-18 7:34 ` gregkh [this message]
2021-02-16 18:54 ` Andreas Dilger
2021-02-17 4:45 ` Nicolas Boichat
2021-02-18 7:42 ` Christoph Hellwig
2021-02-18 9:10 ` Amir Goldstein
2021-02-18 10:29 ` Luis Henriques
2021-02-18 12:15 ` Luis Henriques
2021-02-18 12:49 ` Amir Goldstein
2021-02-18 14:36 ` [PATCH v4] vfs: fix copy_file_range regression in cross-fs copies Luis Henriques
2021-02-18 14:58 ` Amir Goldstein
2021-02-18 15:17 ` [PATCH v5] " Luis Henriques
2021-02-18 15:53 ` Amir Goldstein
2021-02-18 16:35 ` Luis Henriques
2021-02-18 17:18 ` [PATCH v6] " Luis Henriques
2021-02-19 21:18 ` Olga Kornievskaia
2021-02-19 21:52 ` Amir Goldstein
2021-02-21 19:58 ` [PATCH v7] " Luis Henriques
2021-02-22 3:00 ` Nicolas Boichat
2021-02-22 10:24 ` [PATCH v8] " Luis Henriques
2021-02-22 10:46 ` Amir Goldstein
2021-02-22 16:25 ` dai.ngo
2021-02-23 10:32 ` Luis Henriques
2021-02-23 15:28 ` Amir Goldstein
2021-02-23 15:29 ` dai.ngo
2021-02-23 16:02 ` dai.ngo
2021-02-23 16:47 ` Amir Goldstein
2021-02-23 16:57 ` dai.ngo
[not found] ` <e3eed18b-fc7e-e687-608b-7f662017329c@oracle.com>
2021-02-23 17:33 ` Amir Goldstein
2021-02-24 0:13 ` dai.ngo
2021-02-23 17:56 ` Luis Henriques
2021-02-23 17:13 ` Olga Kornievskaia
2021-02-24 1:00 ` Olga Kornievskaia
2021-02-24 10:23 ` Luis Henriques
2021-02-24 10:44 ` Nicolas Boichat
2021-04-09 5:23 ` Nicolas Boichat
2021-04-09 13:39 ` Luis Henriques
2021-04-09 13:50 ` Amir Goldstein
2021-04-23 4:40 ` Nicolas Boichat
2021-05-03 8:54 ` Luis Henriques
2021-02-24 14:23 ` [PATCH] copy_file_range.2: Kernel v5.12 updates Luis Henriques
2021-02-24 16:10 ` Amir Goldstein
2021-02-25 10:21 ` Luis Henriques
2021-02-26 10:13 ` Alejandro Colomar (man-pages)
2021-02-26 10:34 ` Amir Goldstein
2021-02-26 11:15 ` Alejandro Colomar (man-pages)
2021-02-26 13:59 ` Jeff Layton
2021-02-26 21:26 ` Alejandro Colomar (man-pages)
2021-02-26 22:18 ` Alejandro Colomar (man-pages)
2021-02-27 5:41 ` Amir Goldstein
2021-02-27 12:20 ` Alejandro Colomar (man-pages)
2021-02-27 13:49 ` [RFC v2] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-02-27 16:00 ` Amir Goldstein
2021-02-27 23:08 ` [PATCH] copy_file_range.2: Kernel v5.12 updates Steve French
2021-02-28 7:35 ` Amir Goldstein
2021-02-28 22:25 ` Steve French
2021-03-01 6:18 ` Amir Goldstein
2021-03-01 14:41 ` [RFC v3] copy_file_range.2: Update cross-filesystem support for 5.12 Alejandro Colomar
2021-03-01 14:58 ` Amir Goldstein
2021-03-04 9:38 ` [RFC v4] " Alejandro Colomar
2021-03-04 17:13 ` Darrick J. Wong
2021-03-04 18:24 ` Alejandro Colomar (man-pages)
2021-03-04 23:50 ` Darrick J. Wong
2021-02-18 20:41 ` [PATCH v2] vfs: prevent copy_file_range to copy across devices Steve French
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