Messages in this thread Patch in this message | | | Date | Mon, 29 Apr 2002 20:24:46 +0530 | From | Suparna Bhattacharya <> | Subject | [PATCH]Fix: Init page count for all pages during higher order allocs |
| |
The call to set_page_count(page, 1) in page_alloc.c appears to happen only for the first page, for order 1 and higher allocations. This leaves the count for the rest of the pages in that block uninitialised.
We ran into this while working on some lkcd changes where we check the page count to help exclude unreferenced pages, and found that we were missing some referenced pages too (e.g the second page of thread_info/stack pages which involve order 1 allocations)
Here is a patch from Bharata B. Rao that sets the page count for all the pages allocated. This is along the same lines as the code in slab.c to issue SET_PAGE_CACHE/SET_PAGE_SLAB on all the pages in an allocated block based on the slab order. (That code seems to be preceded by a somewhat scary comment so hope there is nothing to be concerned about; are there any caveats ? )
Comments ? Does this look like the right thing to do ?
Regards Suparna
--- 2418-pure/mm/page_alloc.c Tue Feb 26 01:08:14 2002 +++ linux-2.4.18+lkcd/mm/page_alloc.c Mon Apr 29 14:16:37 2002 @@ -181,7 +181,7 @@ static struct page * rmqueue(zone_t *zone, unsigned int order) { free_area_t * area = zone->free_area + order; - unsigned int curr_order = order; + unsigned int i, curr_order = order; struct list_head *head, *curr; unsigned long flags; struct page *page; @@ -206,13 +206,18 @@ page = expand(zone, page, index, order, curr_order, area); spin_unlock_irqrestore(&zone->lock, flags); - set_page_count(page, 1); - if (BAD_RANGE(zone,page)) - BUG(); - if (PageLRU(page)) - BUG(); - if (PageActive(page)) - BUG(); + i = 1UL << order; + page += i; + do { + page--; + set_page_count(page, 1); + if (BAD_RANGE(zone,page)) + BUG(); + if (PageLRU(page)) + BUG(); + if (PageActive(page)) + BUG(); + } while (--i); return page; } curr_order++; @@ -236,6 +241,7 @@ { struct page * page = NULL; int __freed = 0; + unsigned int i; if (!(gfp_mask & __GFP_WAIT)) goto out; @@ -264,25 +270,29 @@ if (tmp->index == order && memclass(tmp->zone, classzone)) { list_del(entry); current->nr_local_pages--; - set_page_count(tmp, 1); - page = tmp; - if (page->buffers) - BUG(); - if (page->mapping) - BUG(); - if (!VALID_PAGE(page)) - BUG(); - if (PageSwapCache(page)) - BUG(); - if (PageLocked(page)) - BUG(); - if (PageLRU(page)) - BUG(); - if (PageActive(page)) - BUG(); - if (PageDirty(page)) - BUG(); + i = 1UL << order; + page = tmp + i; + do { + page--; + set_page_count(page, 1); + if (page->buffers) + BUG(); + if (page->mapping) + BUG(); + if (!VALID_PAGE(page)) + BUG(); + if (PageSwapCache(page)) + BUG(); + if (PageLocked(page)) + BUG(); + if (PageLRU(page)) + BUG(); + if (PageActive(page)) + BUG(); + if (PageDirty(page)) + BUG(); + } while (--i); break; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |