On Mon, Feb 15, 2021 at 10:11 AM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Mon, 2021-02-15 at 15:43 +0000, Luis Henriques wrote: > > Nicolas Boichat reported an issue when trying to use the > > copy_file_range > > syscall on a tracefs file. It failed silently because the file > > content is > > generated on-the-fly (reporting a size of zero) and copy_file_range > > needs > > to know in advance how much data is present. > > That explanation makes no sense whatsoever. copy_file_range is a non- > atomic operation and so the file can change while being copied. Any > determination of 'how much data is present' that is made in advance > would therefore be a flaw in the copy process being used (i.e. > do_splice_direct()). Does sendfile() also 'issue' in the same way? I agree that the explanation of the tracefs problem motivating this patch doesn't make sense. -- Thanks, Steve
