| Message ID | 20210304093806.10589-1-alx.manpages@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC,v4] copy_file_range.2: Update cross-filesystem support for 5.12 | expand |
On Thu, Mar 04, 2021 at 10:38:07AM +0100, Alejandro Colomar wrote: > Linux 5.12 fixes a regression. > > Cross-filesystem (introduced in 5.3) copies were buggy. > > Move the statements documenting cross-fs to BUGS. > Kernels 5.3..5.11 should be patched soon. > > State version information for some errors related to this. > > Reported-by: Luis Henriques <lhenriques@suse.de> > Reported-by: Amir Goldstein <amir73il@gmail.com> > Related: <https://lwn.net/Articles/846403/> > Cc: Greg KH <gregkh@linuxfoundation.org> > Cc: Michael Kerrisk <mtk.manpages@gmail.com> > Cc: Anna Schumaker <anna.schumaker@netapp.com> > Cc: Jeff Layton <jlayton@kernel.org> > Cc: Steve French <sfrench@samba.org> > Cc: Miklos Szeredi <miklos@szeredi.hu> > Cc: Trond Myklebust <trond.myklebust@hammerspace.com> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: "Darrick J. Wong" <darrick.wong@oracle.com> > Cc: Dave Chinner <dchinner@redhat.com> > Cc: Nicolas Boichat <drinkcat@chromium.org> > Cc: Ian Lance Taylor <iant@google.com> > Cc: Luis Lozano <llozano@chromium.org> > Cc: Andreas Dilger <adilger@dilger.ca> > Cc: Olga Kornievskaia <aglo@umich.edu> > Cc: Christoph Hellwig <hch@infradead.org> > Cc: ceph-devel <ceph-devel@vger.kernel.org> > Cc: linux-kernel <linux-kernel@vger.kernel.org> > Cc: CIFS <linux-cifs@vger.kernel.org> > Cc: samba-technical <samba-technical@lists.samba.org> > Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org> > Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org> > Cc: Walter Harms <wharms@bfs.de> > Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> > --- > > v3: > - Don't remove some important text. > - Reword BUGS. > v4: > - Reword. > - Link to BUGS. > > Thanks, Amir, for all the help and better wordings. > > Cheers, > > Alex > > --- > man2/copy_file_range.2 | 27 +++++++++++++++++++++++---- > 1 file changed, 23 insertions(+), 4 deletions(-) > > diff --git a/man2/copy_file_range.2 b/man2/copy_file_range.2 > index 611a39b80..f58bfea8f 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 > +.BR EOPNOTSUPP " (since Linux 5.12)" > +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. > @@ -184,10 +187,17 @@ or > .I fd_out > refers to an active swap file. > .TP > -.B EXDEV > +.BR EXDEV " (before Linux 5.3)" > +The files referred to by > +.IR fd_in " and " fd_out > +are not on the same filesystem. > +.TP > +.BR EXDEV " (since Linux 5.12)" > 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 filesystem, > +and the source and target filesystems are not of the same type, > +or do not support cross-filesystem copy. > .SH VERSIONS > The > .BR copy_file_range () > @@ -200,8 +210,11 @@ Areas of the API that weren't clearly defined were clarified and the API bounds > are much more strictly checked than on earlier kernels. > 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. > +Since Linux 5.12, > +cross-filesystem copies can be achieved > +when both filesystems are of the same type, > +and that filesystem implements support for it. > +See BUGS for behavior prior to 5.12. > .SH CONFORMING TO > The > .BR copy_file_range () > @@ -226,6 +239,12 @@ gives filesystems an opportunity to implement "copy acceleration" techniques, > such as the use of reflinks (i.e., two or more inodes that share > pointers to the same copy-on-write disk blocks) > or server-side-copy (in the case of NFS). > +.SH BUGS > +In Linux kernels 5.3 to 5.11, > +cross-filesystem copies were implemented by the kernel, > +if the operation was not supported by individual filesystems. > +However, on some virtual filesystems, > +the call failed to copy, while still reporting success. ...success, or merely a short copy? (The rest looks reasonable (at least by c_f_r standards) to me.) --D > .SH EXAMPLES > .EX > #define _GNU_SOURCE > -- > 2.30.1.721.g45526154a5 >
Hi Darrick, On 3/4/21 6:13 PM, Darrick J. Wong wrote: > On Thu, Mar 04, 2021 at 10:38:07AM +0100, Alejandro Colomar wrote: >> +However, on some virtual filesystems, >> +the call failed to copy, while still reporting success. > > ...success, or merely a short copy? Okay. > > (The rest looks reasonable (at least by c_f_r standards) to me.) I'm curious, what does "c_f_r standards" mean? :) Cheers, Alex
On Thu, Mar 04, 2021 at 07:24:02PM +0100, Alejandro Colomar (man-pages) wrote: > Hi Darrick, > > On 3/4/21 6:13 PM, Darrick J. Wong wrote: > > On Thu, Mar 04, 2021 at 10:38:07AM +0100, Alejandro Colomar wrote: > > > +However, on some virtual filesystems, > > > +the call failed to copy, while still reporting success. > > > > ...success, or merely a short copy? > > Okay. > > > > > (The rest looks reasonable (at least by c_f_r standards) to me.) > > I'm curious, what does "c_f_r standards" mean? :) c_f_r is shorthand for "copy_file_range". As for standards... well... I'll just say that this being the /second/ major shift in behavior reflects our poor community development processes. The door to general cross-fs copies should not have been thrown open with as little testing as it did. There are legendary dchinner rants about how obviously broken the generic fallback was when it was introduced. There's a reason why we usually wire up new kernel functionality on an opt-in basis, and that is to foster gradual enablement as QA resources permit. It's one thing for maintainers to blow up their own subsystems in isolation, and an entirely different thing to do it between projects with no coordination. Did c_f_r work between an ext4 and an xfs? I have no idea. It seemed to work between xfses of a similar vintage and featureset, at least, but that's about as much testing as I have ever managed. --D > > Cheers, > > Alex > > -- > Alejandro Colomar > Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/ > http://www.alejandro-colomar.es/
diff --git a/man2/copy_file_range.2 b/man2/copy_file_range.2 index 611a39b80..f58bfea8f 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 +.BR EOPNOTSUPP " (since Linux 5.12)" +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. @@ -184,10 +187,17 @@ or .I fd_out refers to an active swap file. .TP -.B EXDEV +.BR EXDEV " (before Linux 5.3)" +The files referred to by +.IR fd_in " and " fd_out +are not on the same filesystem. +.TP +.BR EXDEV " (since Linux 5.12)" 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 filesystem, +and the source and target filesystems are not of the same type, +or do not support cross-filesystem copy. .SH VERSIONS The .BR copy_file_range () @@ -200,8 +210,11 @@ Areas of the API that weren't clearly defined were clarified and the API bounds are much more strictly checked than on earlier kernels. 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. +Since Linux 5.12, +cross-filesystem copies can be achieved +when both filesystems are of the same type, +and that filesystem implements support for it. +See BUGS for behavior prior to 5.12. .SH CONFORMING TO The .BR copy_file_range () @@ -226,6 +239,12 @@ gives filesystems an opportunity to implement "copy acceleration" techniques, such as the use of reflinks (i.e., two or more inodes that share pointers to the same copy-on-write disk blocks) or server-side-copy (in the case of NFS). +.SH BUGS +In Linux kernels 5.3 to 5.11, +cross-filesystem copies were implemented by the kernel, +if the operation was not supported by individual filesystems. +However, on some virtual filesystems, +the call failed to copy, while still reporting success. .SH EXAMPLES .EX #define _GNU_SOURCE
Linux 5.12 fixes a regression. Cross-filesystem (introduced in 5.3) copies were buggy. Move the statements documenting cross-fs to BUGS. Kernels 5.3..5.11 should be patched soon. State version information for some errors related to this. Reported-by: Luis Henriques <lhenriques@suse.de> Reported-by: Amir Goldstein <amir73il@gmail.com> Related: <https://lwn.net/Articles/846403/> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Anna Schumaker <anna.schumaker@netapp.com> Cc: Jeff Layton <jlayton@kernel.org> Cc: Steve French <sfrench@samba.org> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Dave Chinner <dchinner@redhat.com> Cc: Nicolas Boichat <drinkcat@chromium.org> Cc: Ian Lance Taylor <iant@google.com> Cc: Luis Lozano <llozano@chromium.org> Cc: Andreas Dilger <adilger@dilger.ca> Cc: Olga Kornievskaia <aglo@umich.edu> Cc: Christoph Hellwig <hch@infradead.org> Cc: ceph-devel <ceph-devel@vger.kernel.org> Cc: linux-kernel <linux-kernel@vger.kernel.org> Cc: CIFS <linux-cifs@vger.kernel.org> Cc: samba-technical <samba-technical@lists.samba.org> Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org> Cc: Linux NFS Mailing List <linux-nfs@vger.kernel.org> Cc: Walter Harms <wharms@bfs.de> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com> --- v3: - Don't remove some important text. - Reword BUGS. v4: - Reword. - Link to BUGS. Thanks, Amir, for all the help and better wordings. Cheers, Alex --- man2/copy_file_range.2 | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-)