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    SubjectRe: FS-Cache: Add a helper to bulk uncache pages on an inode
    From
    On Thu, Jul 7, 2011 at 22:59, Linux Kernel Mailing List
    <linux-kernel@vger.kernel.org> wrote:
    >    FS-Cache: Add a helper to bulk uncache pages on an inode
    >
    >    Add an FS-Cache helper to bulk uncache pages on an inode.  This will
    >    only work for the circumstance where the pages in the cache correspond
    >    1:1 with the pages attached to an inode's page cache.
    >
    >    This is required for CIFS and NFS: When disabling inode cookie, we were
    >    returning the cookie and setting cifsi->fscache to NULL but failed to
    >    invalidate any previously mapped pages.  This resulted in "Bad page
    >    state" errors and manifested in other kind of errors when running
    >    fsstress.  Fix it by uncaching mapped pages when we disable the inode
    >    cookie.
    >
    >    This patch should fix the following oops and "Bad page state" errors
    >    seen during fsstress testing.

    > --- a/fs/fscache/page.c
    > +++ b/fs/fscache/page.c
    > @@ -954,3 +954,47 @@ void fscache_mark_pages_cached(struct fscache_retrieval *op,
    >        pagevec_reinit(pagevec);
    >  }
    >  EXPORT_SYMBOL(fscache_mark_pages_cached);
    > +
    > +/*
    > + * Uncache all the pages in an inode that are marked PG_fscache, assuming them
    > + * to be associated with the given cookie.
    > + */
    > +void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
    > +                                      struct inode *inode)
    > +{
    > +       struct address_space *mapping = inode->i_mapping;
    > +       struct pagevec pvec;
    > +       pgoff_t next;
    > +       int i;
    > +
    > +       _enter("%p,%p", cookie, inode);
    > +
    > +       if (!mapping || mapping->nrpages == 0) {
    > +               _leave(" [no pages]");
    > +               return;
    > +       }
    > +
    > +       pagevec_init(&pvec, 0);
    > +       next = 0;
    > +       while (next <= (loff_t)-1 &&

    On m68k, I get:

    fs/fscache/page.c: In function ‘__fscache_uncache_all_inode_pages’:
    fs/fscache/page.c:979: warning: comparison is always false due to
    limited range of data type

    next is pgoff_t, which is defined to unsigned long by default, unless
    overridden by the arch
    (hmm, no single arch seems to do that?).
    loff_t is (signed) long long.

    > +              pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)
    > +              ) {
    > +               for (i = 0; i < pagevec_count(&pvec); i++) {
    > +                       struct page *page = pvec.pages[i];
    > +                       pgoff_t page_index = page->index;
    > +
    > +                       ASSERTCMP(page_index, >=, next);
    > +                       next = page_index + 1;
    > +
    > +                       if (PageFsCache(page)) {
    > +                               __fscache_wait_on_page_write(cookie, page);
    > +                               __fscache_uncache_page(cookie, page);
    > +                       }
    > +               }
    > +               pagevec_release(&pvec);
    > +               cond_resched();
    > +       }
    > +
    > +       _leave("");
    > +}

    Gr{oetje,eeting}s,

                            Geert

    --
    Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

    In personal conversations with technical people, I call myself a hacker. But
    when I'm talking to journalists I just say "programmer" or something like that.
                                    -- Linus Torvalds
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