From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: [PATCH v2] md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list Date: Tue, 5 Sep 2017 22:50:13 -0700 Message-ID: <20170906055013.63i4zshqxxtm6x6d@kernel.org> References: <1504666955-15635-1-git-send-email-dennisyang@qnap.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1504666955-15635-1-git-send-email-dennisyang@qnap.com> Sender: linux-raid-owner@vger.kernel.org To: Dennis Yang Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-raid.ids On Wed, Sep 06, 2017 at 11:02:35AM +0800, Dennis Yang wrote: > In release_stripe_plug(), if a stripe_head has its STRIPE_ON_UNPLUG_LIST > set, it indicates that this stripe_head is already in the raid5_plug_cb > list and release_stripe() would be called instead to drop a reference > count. Otherwise, the STRIPE_ON_UNPLUG_LIST bit would be set for this > stripe_head and it will get queued into the raid5_plug_cb list. > > Since break_stripe_batch_list() did not preserve STRIPE_ON_UNPLUG_LIST, > A stripe could be re-added to plug list while it is still on that list > in the following situation. If stripe_head A is added to another > stripe_head B's batch list, in this case A will have its > batch_head != NULL and be added into the plug list. After that, > stripe_head B gets handled and called break_stripe_batch_list() to > reset all the batched stripe_head(including A which is still on > the plug list)'s state and reset their batch_head to NULL. > Before the plug list gets processed, if there is another write request > comes in and get stripe_head A, A will have its batch_head == NULL > (cleared by calling break_stripe_batch_list() on B) and be added to > plug list once again. applied, thanks! > Signed-off-by: Dennis Yang > --- > drivers/md/raid5.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c > index e92dd2d..faf3cfd 100644 > --- a/drivers/md/raid5.c > +++ b/drivers/md/raid5.c > @@ -4611,7 +4611,8 @@ static void break_stripe_batch_list(struct stripe_head *head_sh, > > set_mask_bits(&sh->state, ~(STRIPE_EXPAND_SYNC_FLAGS | > (1 << STRIPE_PREREAD_ACTIVE) | > - (1 << STRIPE_DEGRADED)), > + (1 << STRIPE_DEGRADED) | > + (1 << STRIPE_ON_UNPLUG_LIST)), > head_sh->state & (1 << STRIPE_INSYNC)); > > sh->check_state = head_sh->check_state; > -- > 1.9.1 >