Re: [PATCH] namei: results of d_is_negative() should be checked after dentry revalidation

[Linus Torvalds]

On Fri, Oct 9, 2015 at 10:44 AM, Trond Myklebust
<trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>
> The issue is that revalidation may cause the dentry to be dropped in NFS
> if, say, the client notes that the directory timestamps have changed.

Ack.

We've had this bug before, where we returned something else than
-ENOCHLD while we were doing RCU lookups. See for example commit
97242f99a013 ("link_path_walk(): be careful when failing with
ENOTDIR").

So in general, we should always (a) either verify all sequence points
or (b) return -ENOCHLD to go into slow mode. The patch seems

However, this thing was explicitly made to be this way by commit
766c4cbfacd8 ("namei: d_is_negative() should be checked before ->d_seq
validation"), so while my gut feel is to consider this fix
ObviouslyCorrect(tm), I will delay it a bit in the hope to get an ACK
and comment from Al about the patch.

Al?

                  Linus
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