From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 1 Apr 2004 17:15:34 +0200 From: Andrea Arcangeli Subject: Re: [RFC][PATCH 1/3] radix priority search tree - objrmap complexity fix Message-ID: <20040401151534.GJ18585@dualathlon.random> References: <20040401020126.GW2143@dualathlon.random> <20040401133555.GC18585@dualathlon.random> <20040401150911.GI18585@dualathlon.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040401150911.GI18585@dualathlon.random> Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: Andrew Morton , vrajesh@umich.edu, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: > diff -urNp --exclude CVS --exclude BitKeeper --exclude {arch} --exclude .arch-ids x-ref/mm/page_io.c x/mm/page_io.c > --- x-ref/mm/page_io.c 2004-04-01 17:07:10.231289760 +0200 > +++ x/mm/page_io.c 2004-04-01 17:07:33.182800600 +0200 > @@ -139,7 +139,7 @@ struct address_space_operations swap_aop > > /* > * A scruffy utility function to read or write an arbitrary swap page > - * and wait on the I/O. > + * and wait on the I/O. The caller must have a ref on the page. > */ > int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page) > { > @@ -151,8 +151,16 @@ int rw_swap_page_sync(int rw, swp_entry_ > lock_page(page); > > BUG_ON(page->mapping); > - page->mapping = &swapper_space; > - page->index = entry.val; > + ret = add_to_page_cache(page, &swapper_space, entry.val, GFP_KERNEL); > + if (unlikely(ret)) { > + unlock_page(page); > + return ret; > + } > + /* > + * get one more reference to make page non-exclusive so > + * remove_exclusive_swap_page won't mess with it. > + */ > + page_cache_get(page); > > if (rw == READ) { > ret = swap_readpage(NULL, page); > @@ -161,7 +169,13 @@ int rw_swap_page_sync(int rw, swp_entry_ > ret = swap_writepage(page, &swap_wbc); > wait_on_page_writeback(page); > } > - page->mapping = NULL; > + > + lock_page(page); > + remove_from_page_cache(page); > + unlock_page(page); > + page_cache_release(page); > + page_cache_release(page); /* For add_to_page_cache() */ > + > if (ret == 0 && (!PageUptodate(page) || PageError(page))) > ret = -EIO; > return ret; incrementally to the above I applied this hardness checks in the anon-vma patch, so we're safe against the problem Andrew outlined (somebody attempting to do swapin/swapouts of anonymous pages through that interface, something that shouldn't happen since we want only the VM to deal with userspace mapped pages). @@ -149,8 +149,14 @@ int rw_swap_page_sync(int rw, swp_entry_ }; lock_page(page); - + /* + * This library call can be only used to do I/O + * on _private_ pages just allocated with alloc_pages(). + */ BUG_ON(page->mapping); + BUG_ON(PageSwapCache(page)); + BUG_ON(PageAnon(page)); + BUG_ON(PageLRU(page)); ret = add_to_page_cache(page, &swapper_space, entry.val, GFP_KERNEL); if (unlikely(ret)) { unlock_page(page); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: aart@kvack.org