From: Evgeniy Dushistov <dushistov@mail.ru>
Date: Sat, 5 Aug 2006 19:13:55 +0000 (-0700)
Subject: [PATCH] ufs: ufs_get_locked_page() race fix
X-Git-Tag: v2.6.18-rc4~38
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=1fb32b7bd8203d0175649a75ede3ee7634d6a941;p=linux-2.6-omap-h63xx.git

[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 337cf2c46d1..005d6815adf 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;
 }