On Mon, Jan 13, 2014 at 11:01:32AM +0900, Minchan Kim wrote:
> On Fri, Jan 10, 2014 at 01:10:39PM -0500, Johannes Weiner wrote:
> > shmem mappings already contain exceptional entries where swap slot
> > information is remembered.
> >
> > To be able to store eviction information for regular page cache,
> > prepare every site dealing with the radix trees directly to handle
> > entries other than pages.
> >
> > The common lookup functions will filter out non-page entries and
> > return NULL for page cache holes, just as before. But provide a raw
> > version of the API which returns non-page entries as well, and switch
> > shmem over to use it.
> >
> > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx>
Thanks, Minchan!
> > @@ -890,6 +973,73 @@ repeat:
> > EXPORT_SYMBOL(find_or_create_page);
> >
> > /**
> > + * __find_get_pages - gang pagecache lookup
> > + * @mapping: The address_space to search
> > + * @start: The starting page index
> > + * @nr_pages: The maximum number of pages
> > + * @pages: Where the resulting pages are placed
>
> where is @indices?
Fixed :)
> > @@ -894,6 +894,53 @@ EXPORT_SYMBOL(__pagevec_lru_add);
> >
> > /**
> > * pagevec_lookup - gang pagecache lookup
>
> __pagevec_lookup?
>
> > + * @pvec: Where the resulting entries are placed
> > + * @mapping: The address_space to search
> > + * @start: The starting entry index
> > + * @nr_pages: The maximum number of entries
>
> missing @indices?
>
> > + *
> > + * pagevec_lookup() will search for and return a group of up to
> > + * @nr_pages pages and shadow entries in the mapping. All entries are
> > + * placed in @pvec. pagevec_lookup() takes a reference against actual
> > + * pages in @pvec.
> > + *
> > + * The search returns a group of mapping-contiguous entries with
> > + * ascending indexes. There may be holes in the indices due to
> > + * not-present entries.
> > + *
> > + * pagevec_lookup() returns the number of entries which were found.
>
> __pagevec_lookup
Yikes, all three fixed.
> > @@ -22,6 +22,22 @@
> > #include <linux/cleancache.h>
> > #include "internal.h"
> >
> > +static void clear_exceptional_entry(struct address_space *mapping,
> > + pgoff_t index, void *entry)
> > +{
> > + /* Handled by shmem itself */
> > + if (shmem_mapping(mapping))
> > + return;
> > +
> > + spin_lock_irq(&mapping->tree_lock);
> > + /*
> > + * Regular page slots are stabilized by the page lock even
> > + * without the tree itself locked. These unlocked entries
> > + * need verification under the tree lock.
> > + */
>
> Could you explain why repeated spin_lock with irq disabled isn't problem
> in truncation path?
To modify the cache tree, we have to take the IRQ-safe tree_lock, this
is no different than removing a page (see truncate_complete_page).
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