On Tue, Dec 18, 2007 at 09:59:22PM +0000, Hugh Dickins wrote:
> add_to_swap_cache doesn't amount to much: merge it into its sole caller
> read_swap_cache_async. But we'll be needing to call __add_to_swap_cache
> from shmem.c, so promote it to the new add_to_swap_cache. Both were
> static, so there's no interface confusion to worry about.
>
> And lose that inappropriate "Anon pages are already on the LRU" comment
> in the merging: they're not already on the LRU, as Nick Piggin noticed.
>
> Signed-off-by: Hugh Dickins <[email protected]>
No problems with me. Actually it is nice to make add_to_swap_cache
more closely match add_to_page_cache.
>
> mm/swap_state.c | 53 ++++++++++++++++------------------------------
> 1 file changed, 19 insertions(+), 34 deletions(-)
>
> --- tmpfs1/mm/swap_state.c 2007-12-05 16:42:16.000000000 +0000
> +++ tmpfs2/mm/swap_state.c 2007-12-05 16:42:16.000000000 +0000
> @@ -64,10 +64,10 @@ void show_swap_cache_info(void)
> }
>
> /*
> - * __add_to_swap_cache resembles add_to_page_cache on swapper_space,
> + * add_to_swap_cache resembles add_to_page_cache on swapper_space,
> * but sets SwapCache flag and private instead of mapping and index.
> */
> -static int __add_to_swap_cache(struct page *page, swp_entry_t entry,
> +static int add_to_swap_cache(struct page *page, swp_entry_t entry,
> gfp_t gfp_mask)
> {
> int error;
> @@ -94,28 +94,6 @@ static int __add_to_swap_cache(struct pa
> return error;
> }
>
> -static int add_to_swap_cache(struct page *page, swp_entry_t entry,
> - gfp_t gfp_mask)
> -{
> - int error;
> -
> - BUG_ON(PageLocked(page));
> - if (!swap_duplicate(entry))
> - return -ENOENT;
> -
> - SetPageLocked(page);
> - error = __add_to_swap_cache(page, entry, gfp_mask & GFP_KERNEL);
> - /*
> - * Anon pages are already on the LRU, we don't run lru_cache_add here.
> - */
> - if (error) {
> - ClearPageLocked(page);
> - swap_free(entry);
> - return error;
> - }
> - return 0;
> -}
> -
> /*
> * This must be called only on pages that have
> * been verified to be in the swap cache.
> @@ -165,7 +143,7 @@ int add_to_swap(struct page * page, gfp_
> /*
> * Add it to the swap cache and mark it dirty
> */
> - err = __add_to_swap_cache(page, entry,
> + err = add_to_swap_cache(page, entry,
> gfp_mask|__GFP_NOMEMALLOC|__GFP_NOWARN);
>
> switch (err) {
> @@ -210,7 +188,7 @@ void delete_from_swap_cache(struct page
> */
> int move_to_swap_cache(struct page *page, swp_entry_t entry)
> {
> - int err = __add_to_swap_cache(page, entry, GFP_ATOMIC);
> + int err = add_to_swap_cache(page, entry, GFP_ATOMIC);
> if (!err) {
> remove_from_page_cache(page);
> page_cache_release(page); /* pagecache ref */
> @@ -335,16 +313,21 @@ struct page *read_swap_cache_async(swp_e
> }
>
> /*
> + * Swap entry may have been freed since our caller observed it.
> + */
> + if (!swap_duplicate(entry))
> + break;
> +
> + /*
> * Associate the page with swap entry in the swap cache.
> - * May fail (-ENOENT) if swap entry has been freed since
> - * our caller observed it. May fail (-EEXIST) if there
> - * is already a page associated with this entry in the
> - * swap cache: added by a racing read_swap_cache_async,
> - * or by try_to_swap_out (or shmem_writepage) re-using
> - * the just freed swap entry for an existing page.
> + * May fail (-EEXIST) if there is already a page associated
> + * with this entry in the swap cache: added by a racing
> + * read_swap_cache_async, or add_to_swap or shmem_writepage
> + * re-using the just freed swap entry for an existing page.
> * May fail (-ENOMEM) if radix-tree node allocation failed.
> */
> - err = add_to_swap_cache(new_page, entry, gfp_mask);
> + SetPageLocked(new_page);
> + err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
> if (!err) {
> /*
> * Initiate read into locked page and return.
> @@ -353,7 +336,9 @@ struct page *read_swap_cache_async(swp_e
> swap_readpage(NULL, new_page);
> return new_page;
> }
> - } while (err != -ENOENT && err != -ENOMEM);
> + ClearPageLocked(new_page);
> + swap_free(entry);
> + } while (err != -ENOMEM);
>
> if (new_page)
> page_cache_release(new_page);
--
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