[GFS2] Bug fix to gfs2_readpages()

This fixes a bug where we were releasing a page incorrectly
sometimes when reading a stuffed file. This fixes the bug
that Kevin reported when using Xen.

Cc: Kevin Anderson <kanderso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 27ce30148e69350088215e809a3642ac3253d51d..2c4ec5cf21ffebac2d30a4f36ec295d58645d4bc 100644 (file)
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -249,8 +249,6 @@ out_unlock:
        goto out;
 }
 
-#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
-
 /**
  * gfs2_readpages - Read a bunch of pages at once
  *
@@ -290,7 +288,8 @@ static int gfs2_readpages(struct file *file, struct address_space *mapping,
                struct pagevec lru_pvec;
                pagevec_init(&lru_pvec, 0);
                for (page_idx = 0; page_idx < nr_pages; page_idx++) {
-                       struct page *page = list_to_page(pages);
+                       struct page *page = list_entry(pages->prev, struct page, lru);
+                       prefetchw(&page->flags);
                        list_del(&page->lru);
                        if (!add_to_page_cache(page, mapping,
                                               page->index, GFP_KERNEL)) {
@@ -298,8 +297,9 @@ static int gfs2_readpages(struct file *file, struct address_space *mapping,
                                unlock_page(page);
                                if (!pagevec_add(&lru_pvec, page))
                                         __pagevec_lru_add(&lru_pvec);
+                       } else {
+                               page_cache_release(page);
                        }
-                       page_cache_release(page);
                }
                pagevec_lru_add(&lru_pvec);
                ret = 0;
@@ -321,7 +321,7 @@ out_noerror:
 out_unlock:
        /* unlock all pages, we can't do any I/O right now */
        for (page_idx = 0; page_idx < nr_pages; page_idx++) {
-               struct page *page = list_to_page(pages);
+               struct page *page = list_entry(pages->prev, struct page, lru);
                list_del(&page->lru);
                unlock_page(page);
                page_cache_release(page);