[PATCH 05/43] FS-Cache: Release page->private after failed readahead [ver #46]

[Nick Piggin]

On Thursday 02 April 2009 10:03:47 David Howells wrote:
> The attached patch causes read_cache_pages() to release page-private data
> on a page for which add_to_page_cache() fails or the filler function 
fails.
> This permits pages with caching references associated with them to be
> cleaned up.
>
> The invalidatepage() address space op is called (indirectly) to do the
> honours.

This does not release the page for which the filler function fails.
It releases for all pages that do not get put on the LRU.

I guess that's just a changelog bug.

I don't have a problem with this if it is significantly easier to do
here than the caller -- it should be a slowpath.


>
> Signed-off-by: David Howells <dhowells at redhat.com>
> Acked-by: Steve Dickson <steved at redhat.com>
> Acked-by: Trond Myklebust <Trond.Myklebust at netapp.com>
> ---
>
>  include/linux/page-flags.h |    2 +-
>  mm/readahead.c             |   39 +++++++++++++++++++++++++++++++++++++--
>  2 files changed, 38 insertions(+), 3 deletions(-)
>
>
> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
> index 61df177..9d99e74 100644
> --- a/include/linux/page-flags.h
> +++ b/include/linux/page-flags.h
> @@ -182,7 +182,7 @@ static inline int TestClearPage##uname(struct page
> *page) { return 0; }
>
>  struct page;	/* forward declaration */
>
> -TESTPAGEFLAG(Locked, locked)
> +TESTPAGEFLAG(Locked, locked) TESTSETFLAG(Locked, locked)
>  PAGEFLAG(Error, error)
>  PAGEFLAG(Referenced, referenced) TESTCLEARFLAG(Referenced, referenced)
>  PAGEFLAG(Dirty, dirty) TESTSCFLAG(Dirty, dirty) __CLEARPAGEFLAG(Dirty,
> dirty) diff --git a/mm/readahead.c b/mm/readahead.c
> index 9ce303d..6be9275 100644
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -31,6 +31,41 @@ EXPORT_SYMBOL_GPL(file_ra_state_init);
>
>  #define list_to_page(head) (list_entry((head)->prev, struct page, lru))
>
> +/*
> + * see if a page needs releasing upon read_cache_pages() failure
> + * - the caller of read_cache_pages() may have set PG_private before
> calling, + *   such as the NFS fs marking pages that are cached locally on
> disk, thus we + *   need to give the fs a chance to clean up in the event
> of an error + */
> +static void read_cache_pages_invalidate_page(struct address_space
> *mapping, +					     struct page 
*page)
> +{
> +	if (PagePrivate(page)) {
> +		if (!trylock_page(page))
> +			BUG();
> +		page->mapping = mapping;
> +		do_invalidatepage(page, 0);
> +		page->mapping = NULL;
> +		unlock_page(page);
> +	}
> +	page_cache_release(page);
> +}
> +
> +/*
> + * release a list of pages, invalidating them first if need be
> + */
> +static void read_cache_pages_invalidate_pages(struct address_space
> *mapping, +					      struct 
list_head *pages)
> +{
> +	struct page *victim;
> +
> +	while (!list_empty(pages)) {
> +		victim = list_to_page(pages);
> +		list_del(&victim->lru);
> +		read_cache_pages_invalidate_page(mapping, victim);
> +	}
> +}
> +
>  /**
>   * read_cache_pages - populate an address space with some pages & start
> reads against them * @mapping: the address_space
> @@ -52,14 +87,14 @@ int read_cache_pages(struct address_space *mapping,
> struct list_head *pages, list_del(&page->lru);
>  		if (add_to_page_cache_lru(page, mapping,
>  					page->index, GFP_KERNEL)) 
{
> -			page_cache_release(page);
> +			read_cache_pages_invalidate_page(mapping, 
page);
>  			continue;
>  		}
>  		page_cache_release(page);
>
>  		ret = filler(data, page);
>  		if (unlikely(ret)) {
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