From: Nick Piggin <npiggin@kernel.dk>
Date: Fri, 14 Jan 2011 02:35:53 +0000 (+0000)
Subject: fs: force_reval_path drop rcu-walk before d_invalidate
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bb20c18db6fbb5e6ba499c76473a487d35073467;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

fs: force_reval_path drop rcu-walk before d_invalidate

d_revalidate can return in rcu-walk mode even when it returns 0.  We can't just
call any old dcache function on rcu-walk dentry (the dentry is unstable, so
even through d_lock can safely be taken, the result may no longer be what we
expect -- careful re-checks would be required). So just drop rcu in this case.

(I missed this conversion when switching to the rcu-walk convention that Linus
suggested)

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
---

diff --git a/fs/namei.c b/fs/namei.c
index 19433cdba011..0f02359ce685 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -583,6 +583,13 @@ void release_open_intent(struct nameidata *nd)
 		fput(nd->intent.open.file);
 }
 
+/*
+ * Call d_revalidate and handle filesystems that request rcu-walk
+ * to be dropped. This may be called and return in rcu-walk mode,
+ * regardless of success or error. If -ECHILD is returned, the caller
+ * must return -ECHILD back up the path walk stack so path walk may
+ * be restarted in ref-walk mode.
+ */
 static int d_revalidate(struct dentry *dentry, struct nameidata *nd)
 {
 	int status;
@@ -673,6 +680,9 @@ force_reval_path(struct path *path, struct nameidata *nd)
 		return 0;
 
 	if (!status) {
+		/* Don't d_invalidate in rcu-walk mode */
+		if (nameidata_drop_rcu(nd))
+			return -ECHILD;
 		d_invalidate(dentry);
 		status = -ESTALE;
 	}