On Mon, 20 Oct 2008 20:11:56 +0200 Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:
> +ssize_t generic_file_splice_write_file_nolock(struct pipe_inode_info *pipe,
> + struct file *out, loff_t *ppos,
> + size_t len, unsigned int flags)
> +{
> + struct address_space *mapping = out->f_mapping;
> + struct inode *inode = mapping->host;
> + struct splice_desc sd = {
> + .total_len = len,
> + .flags = flags,
> + .pos = *ppos,
> + .u.file = out,
> + };
> + ssize_t ret;
> +
> + mutex_lock(&pipe->inode->i_mutex);
> + ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
> + mutex_unlock(&pipe->inode->i_mutex);
> +
> + if (ret > 0) {
> + unsigned long nr_pages;
> +
> + *ppos += ret;
> + nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
> +
> + if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(inode))) {
> + int er;
> +
> + er = sync_page_range_nolock(inode, mapping, *ppos, ret);
> + if (er)
> + ret = er;
> + }
> + balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(generic_file_splice_write_file_nolock);
I don't think the balance_dirty_pages() is needed if we just did the
sync_page_range().
But really it'd be better if the throttling happened down in
pipe_to_file(), on a per-page basis. As it stands we can dirty an
arbitrary number of pagecache pages without throttling. I think?
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