From: Amir Goldstein <amir73il@gmail.com>
To: "Alejandro Colomar (man-pages)" <alx.manpages@gmail.com>
Cc: Luis Henriques <lhenriques@suse.de>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Anna Schumaker <anna.schumaker@netapp.com>,
Jeff Layton <jlayton@kernel.org>,
Steve French <sfrench@samba.org>,
Miklos Szeredi <miklos@szeredi.hu>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Dave Chinner <dchinner@redhat.com>,
Greg KH <gregkh@linuxfoundation.org>,
Nicolas Boichat <drinkcat@chromium.org>,
Ian Lance Taylor <iant@google.com>,
Luis Lozano <llozano@chromium.org>,
Andreas Dilger <adilger@dilger.ca>,
Olga Kornievskaia <aglo@umich.edu>,
Christoph Hellwig <hch@infradead.org>,
ceph-devel <ceph-devel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
CIFS <linux-cifs@vger.kernel.org>,
samba-technical <samba-technical@lists.samba.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
linux-man <linux-man@vger.kernel.org>
Subject: Re: [PATCH] copy_file_range.2: Kernel v5.12 updates
Date: Sat, 27 Feb 2021 07:41:18 +0200 [thread overview]
Message-ID: <CAOQ4uxgFCBNwRD7e1srwaVrZMGfOE_JXENL4Q2En52srdj2AYA@mail.gmail.com> (raw)
In-Reply-To: <6b896b29-6fc1-0586-ef31-f2f3298b56b0@gmail.com>
On Sat, Feb 27, 2021 at 12:19 AM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
>
> Hello Amir, Luis,
>
> On 2/24/21 5:10 PM, Amir Goldstein wrote:
> > On Wed, Feb 24, 2021 at 4:22 PM Luis Henriques <lhenriques@suse.de> wrote:
> >>
> >> Update man-page with recent changes to this syscall.
> >>
> >> Signed-off-by: Luis Henriques <lhenriques@suse.de>
> >> ---
> >> Hi!
> >>
> >> Here's a suggestion for fixing the manpage for copy_file_range(). Note that
> >> I've assumed the fix will hit 5.12.
> >>
> >> man2/copy_file_range.2 | 10 +++++++++-
> >> 1 file changed, 9 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/man2/copy_file_range.2 b/man2/copy_file_range.2
> >> index 611a39b8026b..b0fd85e2631e 100644
> >> --- a/man2/copy_file_range.2
> >> +++ b/man2/copy_file_range.2
> >> @@ -169,6 +169,9 @@ Out of memory.
> >> .B ENOSPC
> >> There is not enough space on the target filesystem to complete the copy.
> >> .TP
> >> +.B EOPNOTSUPP
>
> I'll add the kernel version here:
>
> .BR EOPNOTSUPP " (since Linux 5.12)"
Error could be returned prior to 5.3 and would be probably returned
by future stable kernels 5.3..5.12 too
>
> >> +The filesystem does not support this operation >> +.TP
> >> .B EOVERFLOW
> >> The requested source or destination range is too large to represent in the
> >> specified data types.
> >> @@ -187,7 +190,7 @@ refers to an active swap file.
> >> .B EXDEV
> >> The files referred to by
> >> .IR fd_in " and " fd_out
> >> -are not on the same mounted filesystem (pre Linux 5.3).
> >> +are not on the same mounted filesystem (pre Linux 5.3 and post Linux 5.12).
>
> I'm not sure that 'mounted' adds any value here. Would you remove the
> word here?
See rename(2). 'mounted' in this context is explained there.
HOWEVER, it does not fit here.
copy_file_range() IS allowed between two mounts of the same filesystem instance.
To make things more complicated, it appears that cross mount clone is not
allowed via FICLONE/FICLONERANGE ioctl, so ioctl_ficlonerange(2) man page
also uses the 'mounted filesystem' terminology for EXDEV
As things stand now, because of the fallback to clone logic,
copy_file_range() provides a way for users to clone across different mounts
of the same filesystem instance, which they cannot do with the FICLONE ioctl.
Fun :)
BTW, I don't know if preventing cross mount clone was done intentionally,
but as I wrote in a comment in the code once:
/*
* FICLONE/FICLONERANGE ioctls enforce that src and dest files are on
* the same mount. Practically, they only need to be on the same file
* system.
*/
>
> It reads as if two separate devices with the same filesystem type would
> still give this error.
>
> Per the LWN.net article Amir shared, this is permitted ("When called
> from user space, copy_file_range() will only try to copy a file across
> filesystems if the two are of the same type").
>
> This behavior was slightly different before 5.3 AFAICR (was it?) ("until
> then, copy_file_range() refused to copy between files that were not
> located on the same filesystem."). If that's the case, I'd specify the
> difference, or more probably split the error into two, one before 5.3,
> and one since 5.12.
>
True.
> >
> > I think you need to drop the (Linux range) altogether.
>
> I'll keep the range. Users of 5.3..5.11 might be surprised if the
> filesystems are different and they don't get an error, I think.
>
> I reworded it to follow other pages conventions:
>
> .BR EXDEV " (before Linux 5.3; or since Linux 5.12)"
>
> which renders as:
>
> EXDEV (before Linux 5.3; or since Linux 5.12)
> The files referred to by fd_in and fd_out are not on
> the same mounted filesystem.
>
drop 'mounted'
>
> > What's missing here is the NFS cross server copy use case.
> > Maybe:
> >
> > ...are not on the same mounted filesystem and the source and target filesystems
> > do not support cross-filesystem copy.
>
> Yes.
>
> Again, this wasn't true before 5.3, right?
>
Right.
Actually, v5.3 provides the vfs capabilities for filesystems to support
cross fs copy. I am not sure if NFS already implements cross fs copy in
v5.3 and not sure about cifs. Need to get input from nfs/cis developers
or dig in the release notes for server-side copy.
> >
> > You may refer the reader to VERSIONS section where it will say which
> > filesystems support cross-fs copy as of kernel version XXX (i.e. cifs and nfs).
> >
> >> .SH VERSIONS
> >> The
> >> .BR copy_file_range ()
> >> @@ -202,6 +205,11 @@ Applications should target the behaviour and requirements of 5.3 kernels.
> >> .PP
> >> First support for cross-filesystem copies was introduced in Linux 5.3.
> >> Older kernels will return -EXDEV when cross-filesystem copies are attempted.
> >> +.PP
> >> +After Linux 5.12, support for copies between different filesystems was dropped.
> >> +However, individual filesystems may still provide
> >> +.BR copy_file_range ()
> >> +implementations that allow copies across different devices.
> >
> > Again, this is not likely to stay uptodate for very long.
> > The stable kernels are expected to apply your patch (because it fixes
> > a regression)
> > so this should be phrased differently.
> > If it were me, I would provide all the details of the situation to
> > Michael and ask him
> > to write the best description for this section.
>
> I'll look into more detail at this part in a later review.
>
>
> On 2/26/21 11:34 AM, Amir Goldstein wrote:
> > Is this detailed enough? ;-)
> >
> > https://lwn.net/Articles/846403/
>
> Yes, it is!
>
Thanks to LWN :)
Thanks,
Amir.
next prev parent reply other threads:[~2021-02-27 5:42 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
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 [this message]
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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