Re: [RFC][PATCH 1/3] radix priority search tree - objrmap complexity fix

[Andrea Arcangeli <andrea@suse.de>]

On Wed, Mar 31, 2004 at 07:28:51PM +0200, Andrea Arcangeli wrote:
> if they run into trouble I'll return to the pagecache API adding the
> GFP_KERNEL and check for oom failure.

there were troubles with the header indeed. So I went back to the
pagecache version (now fixed with GFP_KERNEL and oom retval checking).

the oops I've got with the header trouble was weird (but at least the
previous radix_tree_delete crash is gone), so it's not completely clear
if this will be enough to make it work as well as it was working before
the -mm writeback changes. I tried to reproduce but apparently acpi is
doing nothing here for a echo 4 > sleep :/.

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 02:09:53.846664248 +0200
+++ x/mm/page_io.c	2004-04-01 02:11:41.526294456 +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 +151,11 @@ 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;
+	}
 
 	if (rw == READ) {
 		ret = swap_readpage(NULL, page);
@@ -161,7 +164,12 @@ 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);	/* For add_to_page_cache() */
+
 	if (ret == 0 && (!PageUptodate(page) || PageError(page)))
 		ret = -EIO;
 	return ret;