Re: [patch 2/4] vfs: add set_page_dirty_notag

[Peter Zijlstra <peterz@infradead.org>]

On Fri, 2009-02-13 at 14:56 +0300, Edward Shishkin wrote:

> ---
>  include/linux/mm.h  |    1 +
>  mm/page-writeback.c |   28 ++++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
> 
> --- mmotm.orig/include/linux/mm.h
> +++ mmotm/include/linux/mm.h
> @@ -841,6 +841,7 @@ int redirty_page_for_writepage(struct wr
>  				struct page *page);
>  int set_page_dirty(struct page *page);
>  int set_page_dirty_lock(struct page *page);
> +int set_page_dirty_notag(struct page *page);
>  int clear_page_dirty_for_io(struct page *page);
>  
>  extern unsigned long move_page_tables(struct vm_area_struct *vma,
> --- mmotm.orig/mm/page-writeback.c
> +++ mmotm/mm/page-writeback.c
> @@ -1248,6 +1248,34 @@ int __set_page_dirty_nobuffers(struct pa
>  EXPORT_SYMBOL(__set_page_dirty_nobuffers);
>  
>  /*
> + * The same as __set_page_dirty_nobuffers, but this function
> + * 1) doesn't tag the page in its radix tree;
> + * 2) makes an assumption that there is no races with truncate.
> + * 3) is not for anonymous or swap pages.
> + */
> +int set_page_dirty_notag(struct page *page)
> +{
> +	struct address_space *mapping = page->mapping;
> +
> +	if (!TestSetPageDirty(page)) {
> +		WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
> +		if (mapping_cap_account_dirty(mapping)) {
> +			preempt_disable();
> +			__inc_zone_page_state(page, NR_FILE_DIRTY);
> +			__inc_bdi_stat(mapping->backing_dev_info,
> +				       BDI_RECLAIMABLE);
> +			task_dirty_inc(current);
> +			task_io_account_write(PAGE_CACHE_SIZE);
> +			preempt_enable();
> +		}
> +		__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
> +		return 1;
> +	}
> +	return 0;
> +}
> +EXPORT_SYMBOL(set_page_dirty_notag);
> +

Eew, so reiser4 will totally side-step the regular vm inode writeback
paths -- or is this fixed by a more elaborate than usual
a_ops->writepages() ?