Before we start changing the page order we better get some debugging
in there that trips us up whenever a wrong order page shows up in a
mapping. This will be helpful for converting new filesystems to
utilize higher orders.

Signed-off-by: Christoph Lameter <[EMAIL PROTECTED]>

---
 mm/filemap.c |   19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

Index: linux-2.6.21-rc7/mm/filemap.c
===================================================================
--- linux-2.6.21-rc7.orig/mm/filemap.c  2007-04-24 11:45:26.000000000 -0700
+++ linux-2.6.21-rc7/mm/filemap.c       2007-04-24 11:46:04.000000000 -0700
@@ -127,6 +127,7 @@ void remove_from_page_cache(struct page 
        struct address_space *mapping = page->mapping;
 
        BUG_ON(!PageLocked(page));
+       VM_BUG_ON(mapping_order(mapping) != compound_order(page));
 
        write_lock_irq(&mapping->tree_lock);
        __remove_from_page_cache(page);
@@ -268,6 +269,7 @@ int wait_on_page_writeback_range(struct 
                        if (page->index > end)
                                continue;
 
+                       VM_BUG_ON(mapping_order(mapping) != 
compound_order(page));
                        wait_on_page_writeback(page);
                        if (PageError(page))
                                ret = -EIO;
@@ -439,6 +441,7 @@ int add_to_page_cache(struct page *page,
 {
        int error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
 
+       VM_BUG_ON(mapping_order(mapping) != compound_order(page));
        if (error == 0) {
                write_lock_irq(&mapping->tree_lock);
                error = radix_tree_insert(&mapping->page_tree, offset, page);
@@ -598,8 +601,10 @@ struct page * find_get_page(struct addre
 
        read_lock_irq(&mapping->tree_lock);
        page = radix_tree_lookup(&mapping->page_tree, offset);
-       if (page)
+       if (page) {
+               VM_BUG_ON(mapping_order(mapping) != compound_order(page));
                page_cache_get(page);
+       }
        read_unlock_irq(&mapping->tree_lock);
        return page;
 }
@@ -624,6 +629,7 @@ struct page *find_lock_page(struct addre
 repeat:
        page = radix_tree_lookup(&mapping->page_tree, offset);
        if (page) {
+               VM_BUG_ON(mapping_order(mapping) != compound_order(page));
                page_cache_get(page);
                if (TestSetPageLocked(page)) {
                        read_unlock_irq(&mapping->tree_lock);
@@ -685,6 +691,7 @@ repeat:
                } else if (err == -EEXIST)
                        goto repeat;
        }
+       VM_BUG_ON(mapping_order(mapping) != compound_order(page));
        if (cached_page)
                page_cache_release(cached_page);
        return page;
@@ -716,8 +723,10 @@ unsigned find_get_pages(struct address_s
        read_lock_irq(&mapping->tree_lock);
        ret = radix_tree_gang_lookup(&mapping->page_tree,
                                (void **)pages, start, nr_pages);
-       for (i = 0; i < ret; i++)
+       for (i = 0; i < ret; i++) {
+               VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
                page_cache_get(pages[i]);
+       }
        read_unlock_irq(&mapping->tree_lock);
        return ret;
 }
@@ -747,6 +756,7 @@ unsigned find_get_pages_contig(struct ad
                if (pages[i]->mapping == NULL || pages[i]->index != index)
                        break;
 
+               VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
                page_cache_get(pages[i]);
                index++;
        }
@@ -774,8 +784,10 @@ unsigned find_get_pages_tag(struct addre
        read_lock_irq(&mapping->tree_lock);
        ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
                                (void **)pages, *index, nr_pages, tag);
-       for (i = 0; i < ret; i++)
+       for (i = 0; i < ret; i++) {
+               VM_BUG_ON(mapping_order(mapping) != compound_order(pages[i]));
                page_cache_get(pages[i]);
+       }
        if (ret)
                *index = pages[ret - 1]->index + 1;
        read_unlock_irq(&mapping->tree_lock);
@@ -2457,6 +2469,7 @@ int try_to_release_page(struct page *pag
        struct address_space * const mapping = page->mapping;
 
        BUG_ON(!PageLocked(page));
+       VM_BUG_ON(mapping_order(mapping) != compound_order(page));
        if (PageWriteback(page))
                return 0;
 

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