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| Started by | Dennis Yang <dennisyang@qnap.com> |
|---|---|
| First post | 2017-09-06 05:10 +0200 |
| Last post | 2017-09-06 08:00 +0200 |
| Articles | 2 — 2 participants |
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[PATCH v2] md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list Dennis Yang <dennisyang@qnap.com> - 2017-09-06 05:10 +0200
Re: [PATCH v2] md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list Shaohua Li <shli@kernel.org> - 2017-09-06 08:00 +0200
| From | Dennis Yang <dennisyang@qnap.com> |
|---|---|
| Date | 2017-09-06 05:10 +0200 |
| Subject | [PATCH v2] md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list |
| Message-ID | <umyT0-3GR-17@gated-at.bofh.it> |
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. Signed-off-by: Dennis Yang <dennisyang@qnap.com> --- 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
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| From | Shaohua Li <shli@kernel.org> |
|---|---|
| Date | 2017-09-06 08:00 +0200 |
| Subject | Re: [PATCH v2] md/raid5: preserve STRIPE_ON_UNPLUG_LIST in break_stripe_batch_list |
| Message-ID | <umBxv-5mw-7@gated-at.bofh.it> |
| In reply to | #1727130 |
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 <dennisyang@qnap.com> > --- > 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 >
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