Messages in this thread | | | Date | Fri, 21 Apr 2006 11:21:58 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] sys_vmsplice |
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On Fri, Apr 21 2006, Andrew Morton wrote: > Jens Axboe <axboe@suse.de> 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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