fs: force_reval_path drop rcu-walk before d_invalidate (bb20c18d) · Commits · 戴 / test

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>

fs/namei.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

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