On Fri, Apr 21 2006, Andrew Morton wrote:
> Jens Axboe <[email protected]> wrote:
> >
> > ...
> >
> > sys_splice() moves data to/from pipes with a file input/output. sys_vmsplice()
> > moves data to a pipe, with the input being a user address range instead.
> >
> > ...
> >
> > +static void *user_page_pipe_buf_map(struct file *file,
> > + struct pipe_inode_info *pipe,
> > + struct pipe_buffer *buf)
> > +{
> > + return kmap(buf->page);
> > +}
> > +
> > +static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,
> > + struct pipe_buffer *buf)
> > +{
> > + kunmap(buf->page);
> > +}
>
> All these new kmaps and kunmaps hurt. It's supposed to be
> kinda-deprecated and scales poorly. Oh well.
I know, it's not a new complaint and I fully agree. It's not too bad to
fix, it just needs 1/2 new pipe_buffer_ops hooks to split the mapping
from the 'checking' part. For now we blissfully ignore highmem boxes and
rejoice on 64-bit machines :-)
> > - while (i < nr_pages)
> > - page_cache_release(pages[i++]);
> > + while (i < spd->nr_pages)
> > + page_cache_release(spd->pages[i++]);
>
> grumble. I'm going to march over there and take away your `i' key. Or
> make it emit "page_nr".
;-)
> > +static long do_vmsplice(struct file *file, void __user *buffer, size_t len,
> > + unsigned int flags)
> > +{
> > + unsigned long uaddr = (unsigned long) buffer;
> > + struct pipe_inode_info *pipe;
> > + struct page *pages[PIPE_BUFFERS];
> > + unsigned int nr_pages;
> > + struct splice_pipe_desc spd = {
> > + .pages = pages,
> > + .len = len,
> > + .flags = flags,
> > + .ops = &user_page_pipe_buf_ops,
> > + };
> > +
> > + pipe = file->f_dentry->d_inode->i_pipe;
> > + if (unlikely(!pipe))
> > + return -EBADF;
> > +
> > + spd.offset = uaddr & ~PAGE_CACHE_MASK;
> > + nr_pages = (len + spd.offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
>
> Can I feed this 16TB of memory? If so, we just overflowed `nr_pages'.
I'll make it a long type instead.
> > --- a/include/asm-powerpc/unistd.h
> > +++ b/include/asm-powerpc/unistd.h
> > @@ -303,8 +303,9 @@ #define __NR_ppoll 281
> > #define __NR_unshare 282
> > #define __NR_splice 283
> > #define __NR_tee 284
> > +#define __NR_vmsplice 285
> >
> > -#define __NR_syscalls 285
> > +#define __NR_syscalls 286
> >
>
> Every time we do this the spufs build breaks:
>
> long spu_sys_callback(struct spu_syscall_block *s)
> {
> long (*syscall)(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
>
> BUILD_BUG_ON(ARRAY_SIZE(spu_syscall_table) != __NR_syscalls);
I'll leave the ppc syscall update out of it.
--
Jens Axboe
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