On Fri, Oct 19, 2018 at 6:30 PM Olga Kornievskaia <olga.kornievskaia@xxxxxxxxx> wrote: > > From: Olga Kornievskaia <kolga@xxxxxxxxxx> > > Allow copy_file_range to copy between different superblocks but only > of the same file system types. This feature was of interest to CIFS > as well as NFS. > > This feature is needed by NFSv4.2 to perform file copy operation on > the same server or file copy between different NFSv4.2 servers. > > If a file system's fileoperations copy_file_range operation prohibits > cross-device copies, fall back to do_splice_direct. This would be > needed for the NFS (destination) server side implementation of the > file copy and currently for CIFS. > > Besides NFS, there is only 1 implementor of the copy_file_range FS > operation -- CIFS. CIFS assumes incoming file descriptors are both > CIFS but it will check if they are coming from different servers and > return error code to fall back to do_splice_direct. > > NFS will allow for copies between different NFS servers. > > Adding to the vfs.txt documentation to explicitly warn about allowing > for different superblocks of the same file type to be passed into the > copy_file_range for the future users of copy_file_range method. > > Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx> > --- > Documentation/filesystems/vfs.txt | 4 +++- > fs/read_write.c | 13 ++++++------- > 2 files changed, 9 insertions(+), 8 deletions(-) > > diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt > index a6c6a8a..5e520de 100644 > --- a/Documentation/filesystems/vfs.txt > +++ b/Documentation/filesystems/vfs.txt > @@ -958,7 +958,9 @@ otherwise noted. > > fallocate: called by the VFS to preallocate blocks or punch a hole. > > - copy_file_range: called by the copy_file_range(2) system call. > + copy_file_range: called by copy_file_range(2) system call. This method > + works on two file descriptors that might reside on > + different superblocks of the same type of file system. > > clone_file_range: called by the ioctl(2) system call for FICLONERANGE and > FICLONE commands. > diff --git a/fs/read_write.c b/fs/read_write.c > index c60790f..474e740 100644 > --- a/fs/read_write.c > +++ b/fs/read_write.c > @@ -1578,10 +1578,6 @@ ssize_t vfs_copy_file_range(struct file *file_in, loff_t pos_in, > (file_out->f_flags & O_APPEND)) > return -EBADF; > > - /* this could be relaxed once a method supports cross-fs copies */ > - if (inode_in->i_sb != inode_out->i_sb) > - return -EXDEV; > - You need to hoist this limitation to clone_file_range() syscall, because you are not allowed to change user facing behavior. Maybe you can later add a uapi flag for copy_file_range() to explicitly allow for cross-sb copy? Maybe you can add the flag now for internal use - only nfsv4 will pass that flag to the vfs helper and system call will verify that flags == 0. Thanks, Amir.
