On Mon, Feb 10, 2014 at 12:54:59PM -0800, Nicholas A. Bellinger wrote:
> Hi Greg,
>
> On Mon, 2014-02-10 at 11:44 -0800, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
> > The patch below does not apply to the 3.13-stable tree.
> > If someone wants it applied there, or to any other stable or longterm
> > tree, then please email the backport, including the original git commit
> > id to <stable@xxxxxxxxxxxxxxx>.
> >
> > thanks,
> >
> > greg k-h
> >
> >
> > ------------------ original commit in Linus's tree ------------------
> >
> > From 5259a06ef97068b710f45d092a587e8d740f750f Mon Sep 17 00:00:00 2001
> > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> > Date: Tue, 28 Jan 2014 17:56:30 -0800
> > Subject: [PATCH] target: Fix percpu_ref_put race in transport_lun_remove_cmd
> >
> > This patch fixes a percpu_ref_put race for se_lun->lun_ref in
> > transport_lun_remove_cmd() where ->lun_ref could end up being
> > put more than once per command via different target completion
> > and fabric release contexts.
> >
> > It adds a cmpxchg() for se_cmd->lun_ref_active to ensure that
> > percpu_ref_put() is only ever called once per se_cmd.
> >
> > This bug was manifesting itself as a LUN shutdown regression
> > bug in >= v3.13 code, where percpu_ref_kill() would end up
> > hanging indefinately due to the incorrect percpu_ref count.
> >
> > (Change se_cmd->lun_ref_active from bool -> int to force at
> > least a 4-byte cmpxchg with MIPS ll/sc ins. - Fengguang)
> >
> > Reported-by: Tommy Apel <tommyapeldk@xxxxxxxxx>
> > Cc: Tommy Apel <tommyapeldk@xxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx> #3.13+
> > Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> >
> > diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> > index 51a9736be726..c50fd9f11aab 100644
> > --- a/drivers/target/target_core_transport.c
> > +++ b/drivers/target/target_core_transport.c
> > @@ -594,10 +594,11 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
> > {
> > struct se_lun *lun = cmd->se_lun;
> >
> > - if (!lun || !cmd->lun_ref_active)
> > + if (!lun)
> > return;
> >
> > - percpu_ref_put(&lun->lun_ref);
> > + if (cmpxchg(&cmd->lun_ref_active, true, false))
> > + percpu_ref_put(&lun->lun_ref);
> > }
> >
> > void transport_cmd_finish_abort(struct se_cmd *cmd, int remove)
> > diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
> > index d28418645b00..909dacbd230f 100644
> > --- a/include/target/target_core_base.h
> > +++ b/include/target/target_core_base.h
> > @@ -552,7 +552,7 @@ struct se_cmd {
> > void *priv;
> >
> > /* Used for lun->lun_ref counting */
> > - bool lun_ref_active;
> > + int lun_ref_active;
> >
> > /* DIF related members */
> > enum target_prot_op prot_op;
> >
>
>
> There is a small context change in target_core_base.h on this one..
>
> Please apply for v3.13.y code.
>
> Thank you,
>
> --nab
>
> diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
> index 91953da..dee2be1 100644
> --- a/drivers/target/target_core_transport.c
> +++ b/drivers/target/target_core_transport.c
> @@ -568,10 +568,11 @@ static void transport_lun_remove_cmd(struct se_cmd *cmd)
> {
> struct se_lun *lun = cmd->se_lun;
>
> - if (!lun || !cmd->lun_ref_active)
> + if (!lun)
> return;
This patch is corrupted and can't be applied at all, please fix your
email client to not convert tabs to spaces :(
Care to try it again?
thanks,
greg k-h
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