[PATCH] ufs: ufs_get_locked_page() race fix

As discussed earlier:
http://lkml.org/lkml/2006/6/28/136
this patch fixes such issue:

`ufs_get_locked_page' takes page from cache
after that `vmtruncate' takes page and deletes it from cache
`ufs_get_locked_page' locks page, and reports about EIO error.

Also because of find_lock_page always return valid page or NULL, we have no
need to check it if page not NULL.

Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 7 deletions

diff --git a/fs/ufs/util.c b/fs/ufs/util.c
index 337cf2c46d10..005d6815adf5 100644
--- a/fs/ufs/util.c
+++ b/fs/ufs/util.c
@@ -257,6 +257,7 @@ try_again:
                 page = read_cache_page(mapping, index,
                                        (filler_t*)mapping->a_ops->readpage,
                                        NULL);
+
                 if (IS_ERR(page)) {
                         printk(KERN_ERR "ufs_change_blocknr: "
                                "read_cache_page error: ino %lu, index: %lu\n",
@@ -266,6 +267,13 @@ try_again:
 
                 lock_page(page);
 
+                if (unlikely(page->mapping == NULL)) {
+                        /* Truncate got there first */
+                        unlock_page(page);
+                        page_cache_release(page);
+                        goto try_again;
+                }
+
                 if (!PageUptodate(page) || PageError(page)) {
                         unlock_page(page);
                         page_cache_release(page);
@@ -275,15 +283,8 @@ try_again:
                                mapping->host->i_ino, index);
 
                         page = ERR_PTR(-EIO);
-                        goto out;
                 }
         }
-
-        if (unlikely(!page->mapping || !page_has_buffers(page))) {
-                unlock_page(page);
-                page_cache_release(page);
-                goto try_again;/*we really need these buffers*/
-        }
 out:
         return page;
 }