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    SubjectRe: [PATCH v4 2/7] deactivate invalidated pages
    On Tue, Dec 07, 2010 at 03:49:24PM +0100, Johannes Weiner wrote:
    > On Mon, Dec 06, 2010 at 02:29:10AM +0900, Minchan Kim wrote:
    > > Changelog since v3:
    > > - Change function comments - suggested by Johannes
    > > - Change function name - suggested by Johannes
    > > - add only dirty/writeback pages to deactive pagevec
    >
    > Why the extra check?
    >
    > > @@ -359,8 +360,16 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
    > > if (lock_failed)
    > > continue;
    > >
    > > - ret += invalidate_inode_page(page);
    > > -
    > > + ret = invalidate_inode_page(page);
    > > + /*
    > > + * If the page is dirty or under writeback, we can not
    > > + * invalidate it now. But we assume that attempted
    > > + * invalidation is a hint that the page is no longer
    > > + * of interest and try to speed up its reclaim.
    > > + */
    > > + if (!ret && (PageDirty(page) || PageWriteback(page)))
    > > + deactivate_page(page);
    >
    > The writeback completion handler does not take the page lock, so you
    > can still miss pages that finish writeback before this test, no?

    Yes. but I think it's rare and even though it happens, it's not critical.
    >
    > Can you explain why you felt the need to add these checks?

    invalidate_inode_page can return 0 although the pages is !{dirty|writeback}.
    Look invalidate_complete_page. As easiest example, if the page has buffer and
    try_to_release_page can't release the buffer, it could return 0.

    I want to check this.

    >
    > Thanks!
    >
    > Hannes

    --
    Kind regards,
    Minchan Kim


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