On Mon, 10 Sep 2007 15:13:19 -0700 (PDT) [email protected] (Paul Menage) wrote:
> Add a BUG_ON() to check for passing an unreferenced dentry to dput().
>
> This is analogous to the similar check in dget(), and will make
> reference-counting bugs in filesystems more immediately obvious. (I
> just spent a while debugging an oops that turned out to be due to
> broken fs reference counting.)
>
> Signed-off-by: Paul Menage <[email protected]>
>
> ---
> fs/dcache.c | 1 +
> 1 file changed, 1 insertion(+)
>
> Index: container-2.6.23-rc3-mm1/fs/dcache.c
> ===================================================================
> --- container-2.6.23-rc3-mm1.orig/fs/dcache.c
> +++ container-2.6.23-rc3-mm1/fs/dcache.c
> @@ -176,6 +176,7 @@ void dput(struct dentry *dentry)
> if (!dentry)
> return;
>
> + BUG_ON(!atomic_read(&dentry->d_count));
> repeat:
> if (atomic_read(&dentry->d_count) == 1)
> might_sleep();
eek, much too aggressive.
I added this:
--- a/fs/dcache.c~add-a-refcount-check-in-dput
+++ a/fs/dcache.c
@@ -176,6 +176,7 @@ void dput(struct dentry *dentry)
if (!dentry)
return;
+ WARN_ON_ONCE(!atomic_read(&dentry->d_count));
repeat:
if (atomic_read(&dentry->d_count) == 1)
might_sleep();
_
to the -mm-only-debugging-patches section of the -mm tree.
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