linux-kernel - [PATCH]: ufs: ufs_get_locked

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Date:	Mon, 31 Jul 2006 16:57:02 +0400
From:	Evgeniy Dushistov <dushistov@...l.ru>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:	Andrew Morton <akpm@...l.org>
Subject: [PATCH]: ufs: ufs_get_locked_patch 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 check it if page not NULL.

Signed-off-by: Evgeniy Dushistov <dushistov@...l.ru>


---


Index: linux-2.6.18-rc2-mm1/fs/ufs/util.c
===================================================================
--- linux-2.6.18-rc2-mm1.orig/fs/ufs/util.c
+++ linux-2.6.18-rc2-mm1/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 != mapping ||
+			     page->index != index)) {
+			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;
 }

-- 
/Evgeniy

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