[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>

diff --git a/fs/ufs/util.c b/fs/ufs/util.c
index 337cf2c..005d681 100644 (file)
--- 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;
 }