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    SubjectRe: [PATCH 09/28] FS-Cache: Release page->private after failed readahead [try #2]
    Date
    On Thursday 06 December 2007 06:39, 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 is pretty nasty. I would suggest either to have the function
    return the number of pages that were added to pagecache, or just
    open code it.

    >
    > Signed-off-by: David Howells <dhowells@redhat.com>
    > ---
    >
    > mm/readahead.c | 39 +++++++++++++++++++++++++++++++++++++--
    > 1 files changed, 37 insertions(+), 2 deletions(-)
    >
    > diff --git a/mm/readahead.c b/mm/readahead.c
    > index c9c50ca..75aa6b6 100644
    > --- a/mm/readahead.c
    > +++ b/mm/readahead.c
    > @@ -44,6 +44,41 @@ 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 (TestSetPageLocked(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
    > @@ -65,14 +100,14 @@ 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)) {
    > - put_pages_list(pages);
    > + read_cache_pages_invalidate_pages(mapping, pages);
    > break;
    > }
    > task_io_account_read(PAGE_CACHE_SIZE);
    >


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