On Wed, May 29, 2019 at 5:03 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>
> On Wed, May 29, 2019 at 11:09 PM Olga Kornievskaia
> <olga.kornievskaia@xxxxxxxxx> wrote:
> >
> > On Wed, May 29, 2019 at 1:43 PM Amir Goldstein <amir73il@xxxxxxxxx> 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@xxxxxxxxxxxxx>
> > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> > > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> > > Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > ---
> > > 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.
> >
>
> That will require more delicate patches to filesystems.
> Are you saying there is a *good* reason to do that now?
> Is nfs copy offload expected to be between different types of nfs
> file_system_type?
So I had to setup a test case to perhaps give you a good reason. An
NFS server might have an export that's a referral to another server.
In this case the NFS client gets an ERR_MOVED and would mount the 2nd
server. It shows up as a submount and it would have a different file
system type. Having that check would prevent the NFS client from doing
an NFS copy_file_range between those 2 servers and instead VFS would
fallback to the generic_copy_file_range.
So why is hard(er) to push the check that ->s_types are the same for
the input and output files into the filesystems like it's done in this
patch with the ->i_sb checks?
