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From:   Olga Kornievskaia <olga.kornievskaia@gmail.com>
Date:   Wed, 29 May 2019 16:09:41 -0400
Message-ID: <CAN-5tyF9OnRsF_dgtx8aUGFB5tUUs=JK1wzXvRGo3za8jfpJdQ@mail.gmail.com>
Subject: Re: [PATCH v3 13/13] vfs: allow copy_file_range to copy across devices
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     "Darrick J . Wong" <darrick.wong@oracle.com>,
        Dave Chinner <david@fromorbit.com>,
        Christoph Hellwig <hch@lst.de>,
        linux-xfs <linux-xfs@vger.kernel.org>,
        Luis Henriques <lhenriques@suse.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        ceph-devel@vger.kernel.org, linux-nfs <linux-nfs@vger.kernel.org>,
        CIFS <linux-cifs@vger.kernel.org>,
        Steve French <stfrench@microsoft.com>,
        Dave Chinner <dchinner@redhat.com>
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Sender: linux-nfs-owner@vger.kernel.org
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On Wed, May 29, 2019 at 1:43 PM Amir Goldstein <amir73il@gmail.com> wrote:
>
> We want to enable cross-filesystem copy_file_range functionality
> where possible, so push the "same superblock only" checks down to
> the individual filesystem callouts so they can make their own
> decisions about cross-superblock copy offload and fallack to
> generic_copy_file_range() for cross-superblock copy.
>
> [Amir] We do not call ->remap_file_range() in case the inodes are not
> on the same sb and do not call ->copy_file_range() in case the inodes
> are not on the same filesystem type.
>
> This changes behavior of the copy_file_range(2) syscall, which will
> now allow cross filesystem in-kernel copy.  CIFS already supports
> cross-superblock copy, between two shares to the same server. This
> functionality will now be available via the copy_file_range(2) syscall.
>
> Cc: Steve French <stfrench@microsoft.com>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/ceph/file.c    |  4 +++-
>  fs/cifs/cifsfs.c  |  2 +-
>  fs/fuse/file.c    |  5 ++++-
>  fs/nfs/nfs4file.c |  5 ++++-
>  fs/read_write.c   | 20 ++++++++++++++------
>  5 files changed, 26 insertions(+), 10 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index 8a70708e1aca..e9614d686301 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1909,6 +1909,8 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
>
>         if (src_inode == dst_inode)
>                 return -EINVAL;
> +       if (src_inode->i_sb != dst_inode->i_sb)
> +               return -EXDEV;
>         if (ceph_snap(dst_inode) != CEPH_NOSNAP)
>                 return -EROFS;
>
> @@ -2126,7 +2128,7 @@ static ssize_t ceph_copy_file_range(struct file *src_file, loff_t src_off,
>         ret = __ceph_copy_file_range(src_file, src_off, dst_file, dst_off,
>                                      len, flags);
>
> -       if (ret == -EOPNOTSUPP)
> +       if (ret == -EOPNOTSUPP || ret == -EXDEV)
>                 ret = generic_copy_file_range(src_file, src_off, dst_file,
>                                               dst_off, len, flags);
>         return ret;
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index ab6c5c24146d..83956452c108 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -1154,7 +1154,7 @@ static ssize_t cifs_copy_file_range(struct file *src_file, loff_t off,
>                                         len, flags);
>         free_xid(xid);
>
> -       if (rc == -EOPNOTSUPP)
> +       if (rc == -EOPNOTSUPP || rc == -EXDEV)
>                 rc = generic_copy_file_range(src_file, off, dst_file,
>                                              destoff, len, flags);
>         return rc;
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 7f33d68f66d9..eab00cd089e8 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -3126,6 +3126,9 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
>         if (fc->no_copy_file_range)
>                 return -EOPNOTSUPP;
>
> +       if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> +               return -EXDEV;
> +
>         inode_lock(inode_out);
>
>         err = file_modified(file_out);
> @@ -3187,7 +3190,7 @@ static ssize_t fuse_copy_file_range(struct file *src_file, loff_t src_off,
>         ret = __fuse_copy_file_range(src_file, src_off, dst_file, dst_off,
>                                      len, flags);
>
> -       if (ret == -EOPNOTSUPP)
> +       if (ret == -EOPNOTSUPP || ret == -EXDEV)
>                 ret = generic_copy_file_range(src_file, src_off, dst_file,
>                                               dst_off, len, flags);
>         return ret;
> diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
> index 4842f3ab3161..f4157eb1f69d 100644
> --- a/fs/nfs/nfs4file.c
> +++ b/fs/nfs/nfs4file.c
> @@ -133,6 +133,9 @@ static ssize_t __nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
>                                       struct file *file_out, loff_t pos_out,
>                                       size_t count, unsigned int flags)
>  {
> +       /* Only offload copy if superblock is the same */
> +       if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> +               return -EXDEV;
>         if (!nfs_server_capable(file_inode(file_out), NFS_CAP_COPY))
>                 return -EOPNOTSUPP;
>         if (file_inode(file_in) == file_inode(file_out))
> @@ -148,7 +151,7 @@ static ssize_t nfs4_copy_file_range(struct file *file_in, loff_t pos_in,
>
>         ret = __nfs4_copy_file_range(file_in, pos_in, file_out, pos_out, count,
>                                      flags);
> -       if (ret == -EOPNOTSUPP)
> +       if (ret == -EOPNOTSUPP || ret == -EXDEV)
>                 ret = generic_copy_file_range(file_in, pos_in, file_out,
>                                               pos_out, count, flags);
>         return ret;
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 706ea5f276a7..d8930bb735cb 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1618,7 +1618,18 @@ static ssize_t do_copy_file_range(struct file *file_in, loff_t pos_in,
>                                   struct file *file_out, loff_t pos_out,
>                                   size_t len, unsigned int flags)
>  {
> -       if (file_out->f_op->copy_file_range)
> +       /*
> +        * Although we now allow filesystems to handle cross sb copy, passing
> +        * an inode of the wrong filesystem type to filesystem operation can
> +        * often result in an attempt to dereference the wrong concrete inode
> +        * struct, so avoid doing that until we really have a good reason.
> +        * The incentive for passing inode from different sb to filesystem is
> +        * NFS cross server copy and for that use case, enforcing same
> +        * filesystem type is acceptable.
> +        */
> +       if (file_out->f_op->copy_file_range &&
> +           file_inode(file_in)->i_sb->s_type ==
> +           file_inode(file_out)->i_sb->s_type)

While I'm not sure how much I care (vs wanting at least this much of
cross device copy available) but in NFS there are several NFS
file_system_type defined which would disallow a copy between them
(like nfs4_remote_fs_type, nfs4_remote_referral_fs_type, and good old
nfs4_fs_type).

One idea would be to push the check into the filesystems themselves.

>                 return file_out->f_op->copy_file_range(file_in, pos_in,
>                                                        file_out, pos_out,
>                                                        len, flags);
> @@ -1641,10 +1652,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
>         if (flags != 0)
>                 return -EINVAL;
>
> -       /* this could be relaxed once a method supports cross-fs copies */
> -       if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
> -               return -EXDEV;
> -
>         ret = generic_copy_file_checks(file_in, pos_in, file_out, pos_out, &len,
>                                        flags);
>         if (unlikely(ret))
> @@ -1667,7 +1674,8 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in,
>          * Try cloning first, this is supported by more file systems, and
>          * more efficient if both clone and copy are supported (e.g. NFS).
>          */
> -       if (file_in->f_op->remap_file_range) {
> +       if (file_in->f_op->remap_file_range &&
> +           file_inode(file_in)->i_sb == file_inode(file_out)->i_sb) {
>                 loff_t cloned;
>
>                 cloned = file_in->f_op->remap_file_range(file_in, pos_in,
> --
> 2.17.1
>