Re: [PATCH v3 3/3] mm: Wait for writeback when grabbing pages to begin a write

Christoph Hellwig
2011-05-04T18:48:15Z

On Wed, May 04, 2011 at 10:42:27AM -0700, Darrick J. Wong wrote:
> When grabbing a page for a buffered IO write, the mm should wait for writeback
> on the page to complete so that the page does not become writable during the IO
> operation.
>
> Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
> ---
>
> mm/filemap.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index c641edf..c22675f 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -2287,8 +2287,10 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
> gfp_notmask = __GFP_FS;
> repeat:
> page = find_lock_page(mapping, index);
> - if (page)
> + if (page) {
> + wait_on_page_writeback(page);
> return page;
> + }

goto found;

>
> page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~gfp_notmask);
> if (!page)
> @@ -2301,6 +2303,7 @@ repeat:
> goto repeat;
> return NULL;
> }

found:
> + wait_on_page_writeback(page);
> return page;
> }
> EXPORT_SYMBOL(grab_cache_page_write_begin);