The btrfs clone ioctls are now adopted by other file systems, with NFS
and CIFS already having support for them, and XFS being under active
development.  To avoid growth of various slightly incompatible
implementations, add one to the VFS.  Note that clones are different from
file copies in several ways:

 - they are atomic vs other writers
 - they support whole file clones
 - they support 64-bit legth clones
 - they do not allow partial success (aka short writes)
 - clones are expected to be a fast metadata operation

Because of that it would be rather cumbersome to try to piggyback them on
top of the recent clone_file_range infrastructure.  The converse isn't
true and the clone_file_range system call could try clone file range as
a first attempt to copy, something that further patches will enable.

Based on earlier work from Peng Tao.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

FSCTL_SRV_COPYCHUNK_WRITE only requires that the source and target
be on the same server (not the same volume or same share),
so relax the existing check (which required them to be on
the same share). Note that this works to Windows (and presumably
most other NAS) but Samba requires that the source
and target be on the same share.  Moving a file across
shares is a common use case and can be very heplful (100x faster).

Signed-off-by: Steve French <steve.french@primarydata.com>
Reviewed-by: David Disseldorp <ddiss@samba.org>

This might lead to local privilege escalation (code execution as
kernel) for systems where the following conditions are met:

 - CONFIG_CIFS_SMB2 and CONFIG_CIFS_POSIX are enabled
 - a cifs filesystem is mounted where:
  - the mount option "vers" was used and set to a value >=2.0
  - the attacker has write access to at least one file on the filesystem

To attack this, an attacker would have to guess the target_tcon
pointer (but guessing wrong doesn't cause a crash, it just returns an
error code) and win a narrow race.

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Jann Horn <jann@thejh.net>
Signed-off-by: Steve French <smfrench@gmail.com>

The server exports information about the share and underlying
device under an SMB3 export, including its attributes and
capabilities, which is stored by cifs.ko when first connecting
to the share.

Add ioctl to cifs.ko to allow user space smb3 helper utilities
(in cifs-utils) to display this (e.g. via smb3util).

This information is also useful for debugging and for
resolving configuration errors.

Signed-off-by: Steve French <steve.french@primarydata.com>

set integrity increases reliability of files stored on SMB3 servers.
Add ioctl to allow setting this on files on SMB3 and later mounts.

Signed-off-by: Steve French <steve.french@primarydata.com>

 Getting fantastic copy performance with cp --reflink over SMB3.11
 using the new FSCTL_DUPLICATE_EXTENTS.

 This FSCTL was added in the SMB3.11 dialect (testing was
 against REFS file system) so have put it as a 3.11 protocol
 specific operation ("vers=3.1.1" on the mount).  Tested at
 the SMB3 plugfest in Redmond.

 It depends on the new FS Attribute (BLOCK_REFCOUNTING) which
 is used to advertise support for the ability to do this ioctl
 (if you can support multiple files pointing to the same block
 than this refcounting ability or equivalent is needed to
 support the new reflink-like duplicate extent SMB3 ioctl.

Signed-off-by: Steve French <steve.french@primarydata.com>

It really needs to check that src is non-directory *and* use
{un,}lock_two_nodirectories().  As it is, it's trivial to cause
double-lock (ioctl(fd, CIFS_IOC_COPYCHUNK_FILE, fd)) and if the
last argument is an fd of directory, we are asking for trouble
by violating the locking order - all directories go before all
non-directories.  If the last argument is an fd of parent
directory, it has 50% odds of locking child before parent,
which will cause AB-BA deadlock if we race with unlink().

Cc: stable@vger.kernel.org @ 3.13+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Libo Chen <clbchenlibo.chen@huawei.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

Change cifs.ko to using CIFS_IOCTL_COPYCHUNK instead
of BTRFS_IOC_CLONE to avoid confusion about whether
copy-on-write is required or optional for this operation.

SMB2/SMB3 copyoffload had used the BTRFS_IOC_CLONE ioctl since
they both speed up copy by offloading the copy rather than
passing many read and write requests back and forth and both have
identical syntax (passing file handles), but for SMB2/SMB3
CopyChunk the server is not required to use copy-on-write
to make a copy of the file (although some do), and Christoph
has commented that since CopyChunk does not require
copy-on-write we should not reuse BTRFS_IOC_CLONE.

This patch renames the ioctl to use a cifs specific IOCTL
CIFS_IOCTL_COPYCHUNK.  This ioctl is particularly important
for SMB2/SMB3 since large file copy over the network otherwise
can be very slow, and with this is often more than 100 times
faster putting less load on server and client.

Note that if a copy syscall is ever introduced, depending on
its requirements/format it could end up using one of the other
three methods that CIFS/SMB2/SMB3 can do for copy offload,
but this method is particularly useful for file copy
and broadly supported (not just by Samba server).

Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: David Disseldorp <ddiss@samba.org>

This first patch adds the ability for us to do a server side copy
(ie fast copy offloaded to the server to perform, aka refcopy)

"cp --reflink"

of one file to another located on the same server.  This
is much faster than traditional copy (which requires
reading and writing over the network and extra
memcpys).

This first version is not going to be copy
files larger than about 1MB (to Samba) until I add
support for multiple chunks and for autoconfiguring
the chunksize.

It includes:
1) processing of the ioctl
2) marshalling and sending the SMB2/SMB3 fsctl over the network
3) simple parsing of the response

It does not include yet (these will be in followon patches to come soon):
1) support for multiple chunks
2) support for autoconfiguring and remembering the chunksize
3) Support for the older style copychunk which Samba 4.1 server supports
(because this requires write permission on the target file, which
cp does not give you, apparently per-posix).  This may require
a distinct tool (other than cp) and other ioctl to implement.

Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>