| Message ID | 20210622121551.3398730-45-willy@infradead.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Folio-enabling the page cache | expand |
On Tue, Jun 22, 2021 at 01:15:49PM +0100, Matthew Wilcox (Oracle) wrote: > - * Return: The head page or shadow entry, %NULL if nothing is found. > + * Return: The folio, swap or shadow entry, %NULL if nothing is found. This (old and new) reads a little weird, given that it returns a struct folio, even if that happens to be a magic entry. Otherwise looks good: Reviewed-by: Christoph Hellwig <hch@lst.de>
On Wed, Jun 23, 2021 at 01:32:39PM +0200, Christoph Hellwig wrote: > On Tue, Jun 22, 2021 at 01:15:49PM +0100, Matthew Wilcox (Oracle) wrote: > > - * Return: The head page or shadow entry, %NULL if nothing is found. > > + * Return: The folio, swap or shadow entry, %NULL if nothing is found. > > This (old and new) reads a little weird, given that it returns a > struct folio, even if that happens to be a magic entry. Yeah. How about this? - * Return: The head page or shadow entry, %NULL if nothing is found. + * Return: The folio, swap or shadow entry, %NULL if nothing is found. */ -static struct page *mapping_get_entry(struct address_space *mapping, - pgoff_t index) +static void *mapping_get_entry(struct address_space *mapping, pgoff_t index) { I still use a struct folio in mapping_get_entry(), but this means that pagecache_get_page() doesn't change in this patch.
On Fri, Jun 25, 2021 at 04:29:47AM +0100, Matthew Wilcox wrote: > > > - * Return: The head page or shadow entry, %NULL if nothing is found. > > > + * Return: The folio, swap or shadow entry, %NULL if nothing is found. > > > > This (old and new) reads a little weird, given that it returns a > > struct folio, even if that happens to be a magic entry. > > Yeah. How about this? > > - * Return: The head page or shadow entry, %NULL if nothing is found. > + * Return: The folio, swap or shadow entry, %NULL if nothing is found. > */ > -static struct page *mapping_get_entry(struct address_space *mapping, > - pgoff_t index) > +static void *mapping_get_entry(struct address_space *mapping, pgoff_t index) > { > > I still use a struct folio in mapping_get_entry(), but this means that > pagecache_get_page() doesn't change in this patch. Much better, thanks.
diff --git a/mm/filemap.c b/mm/filemap.c index a174f8ce87ea..7d0b51f30223 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1754,49 +1754,43 @@ EXPORT_SYMBOL(page_cache_prev_miss); * @mapping: the address_space to search * @index: The page cache index. * - * Looks up the page cache slot at @mapping & @index. If there is a - * page cache page, the head page is returned with an increased refcount. + * Looks up the page cache entry at @mapping & @index. If it is a folio, + * it is returned with an increased refcount. If it is a shadow entry + * of a previously evicted folio, or a swap entry from shmem/tmpfs, + * it is returned without further action. * - * If the slot holds a shadow entry of a previously evicted page, or a - * swap entry from shmem/tmpfs, it is returned. - * - * Return: The head page or shadow entry, %NULL if nothing is found. + * Return: The folio, swap or shadow entry, %NULL if nothing is found. */ -static struct page *mapping_get_entry(struct address_space *mapping, +static struct folio *mapping_get_entry(struct address_space *mapping, pgoff_t index) { XA_STATE(xas, &mapping->i_pages, index); - struct page *page; + struct folio *folio; rcu_read_lock(); repeat: xas_reset(&xas); - page = xas_load(&xas); - if (xas_retry(&xas, page)) + folio = xas_load(&xas); + if (xas_retry(&xas, folio)) goto repeat; /* * A shadow entry of a recently evicted page, or a swap entry from * shmem/tmpfs. Return it without attempting to raise page count. */ - if (!page || xa_is_value(page)) + if (!folio || xa_is_value(folio)) goto out; - if (!page_cache_get_speculative(page)) + if (!folio_try_get_rcu(folio)) goto repeat; - /* - * Has the page moved or been split? - * This is part of the lockless pagecache protocol. See - * include/linux/pagemap.h for details. - */ - if (unlikely(page != xas_reload(&xas))) { - put_page(page); + if (unlikely(folio != xas_reload(&xas))) { + folio_put(folio); goto repeat; } out: rcu_read_unlock(); - return page; + return folio; } /** @@ -1836,10 +1830,12 @@ static struct page *mapping_get_entry(struct address_space *mapping, struct page *pagecache_get_page(struct address_space *mapping, pgoff_t index, int fgp_flags, gfp_t gfp_mask) { + struct folio *folio; struct page *page; repeat: - page = mapping_get_entry(mapping, index); + folio = mapping_get_entry(mapping, index); + page = &folio->page; if (xa_is_value(page)) { if (fgp_flags & FGP_ENTRY) return page;
The pagecache only contains folios, so indicate that this is definitely not a tail page. Shrinks mapping_get_entry() by 56 bytes, but grows pagecache_get_page() by 21 bytes as gcc makes slightly different hot/cold code decisions. A net reduction of 35 bytes of text. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/filemap.c | 38 +++++++++++++++++--------------------- 1 file changed, 17 insertions(+), 21 deletions(-)