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SubjectRe: [PATCH v4 2/2] mpt2sas: Refcount fw_events and fix unsafe list usage
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On Fri, Aug 14, 2015 at 7:18 AM, Calvin Owens <calvinowens@fb.com> wrote:
> The fw_event_work struct is concurrently referenced at shutdown, so
> add a refcount to protect it, and refactor the code to use it.
>
> Additionally, refactor _scsih_fw_event_cleanup_queue() such that it
> no longer iterates over the list without holding the lock, since
> _firmware_event_work() concurrently deletes items from the list.
>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Calvin Owens <calvinowens@fb.com>

Tested-by: Chaitra Basappa <chaitra.basappa@avagotech.com>
ACK-by: Sreekanth Reddy <sreekanth.reddy@avagotech.com>

> ---
> Changes in v4: None
>
> Changes in v3:
> * Add a break condition to the REMOVE_UNRESPONDING_DEVICES fw_event,
> which can loop over a sleep forever (5m+ at least) at unloading. I
> don't think anything prevented this before, but taking the fw_event
> object off the list at the top of _firmware_event_work() seems to have
> made it more likely to happen.
>
> Changes in v2:
> * Squished patches 4-6 into one patch
> * Remove the fw_event from fw_event_list at the start of
> _firmware_event_work()
> * Explicitly seperate fw_event_list removal from fw_event freeing
>
> drivers/scsi/mpt2sas/mpt2sas_scsih.c | 112 ++++++++++++++++++++++++++++-------
> 1 file changed, 91 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/scsi/mpt2sas/mpt2sas_scsih.c b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> index 5eca3a4..c0ff55b 100644
> --- a/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> +++ b/drivers/scsi/mpt2sas/mpt2sas_scsih.c
> @@ -176,9 +176,37 @@ struct fw_event_work {
> u8 VP_ID;
> u8 ignore;
> u16 event;
> + struct kref refcount;
> char event_data[0] __aligned(4);
> };
>
> +static void fw_event_work_free(struct kref *r)
> +{
> + kfree(container_of(r, struct fw_event_work, refcount));
> +}
> +
> +static void fw_event_work_get(struct fw_event_work *fw_work)
> +{
> + kref_get(&fw_work->refcount);
> +}
> +
> +static void fw_event_work_put(struct fw_event_work *fw_work)
> +{
> + kref_put(&fw_work->refcount, fw_event_work_free);
> +}
> +
> +static struct fw_event_work *alloc_fw_event_work(int len)
> +{
> + struct fw_event_work *fw_event;
> +
> + fw_event = kzalloc(sizeof(*fw_event) + len, GFP_ATOMIC);
> + if (!fw_event)
> + return NULL;
> +
> + kref_init(&fw_event->refcount);
> + return fw_event;
> +}
> +
> /* raid transport support */
> static struct raid_template *mpt2sas_raid_template;
>
> @@ -2872,36 +2900,39 @@ _scsih_fw_event_add(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work *fw_event)
> return;
>
> spin_lock_irqsave(&ioc->fw_event_lock, flags);
> + fw_event_work_get(fw_event);
> list_add_tail(&fw_event->list, &ioc->fw_event_list);
> INIT_DELAYED_WORK(&fw_event->delayed_work, _firmware_event_work);
> + fw_event_work_get(fw_event);
> queue_delayed_work(ioc->firmware_event_thread,
> &fw_event->delayed_work, 0);
> spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
> }
>
> /**
> - * _scsih_fw_event_free - delete fw_event
> + * _scsih_fw_event_del_from_list - delete fw_event from the list
> * @ioc: per adapter object
> * @fw_event: object describing the event
> * Context: This function will acquire ioc->fw_event_lock.
> *
> - * This removes firmware event object from link list, frees associated memory.
> + * If the fw_event is on the fw_event_list, remove it and do a put.
> *
> * Return nothing.
> */
> static void
> -_scsih_fw_event_free(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work
> +_scsih_fw_event_del_from_list(struct MPT2SAS_ADAPTER *ioc, struct fw_event_work
> *fw_event)
> {
> unsigned long flags;
>
> spin_lock_irqsave(&ioc->fw_event_lock, flags);
> - list_del(&fw_event->list);
> - kfree(fw_event);
> + if (!list_empty(&fw_event->list)) {
> + list_del_init(&fw_event->list);
> + fw_event_work_put(fw_event);
> + }
> spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
> }
>
> -
> /**
> * _scsih_error_recovery_delete_devices - remove devices not responding
> * @ioc: per adapter object
> @@ -2916,13 +2947,14 @@ _scsih_error_recovery_delete_devices(struct MPT2SAS_ADAPTER *ioc)
> if (ioc->is_driver_loading)
> return;
>
> - fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
> + fw_event = alloc_fw_event_work(0);
> if (!fw_event)
> return;
>
> fw_event->event = MPT2SAS_REMOVE_UNRESPONDING_DEVICES;
> fw_event->ioc = ioc;
> _scsih_fw_event_add(ioc, fw_event);
> + fw_event_work_put(fw_event);
> }
>
> /**
> @@ -2936,12 +2968,29 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc)
> {
> struct fw_event_work *fw_event;
>
> - fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
> + fw_event = alloc_fw_event_work(0);
> if (!fw_event)
> return;
> fw_event->event = MPT2SAS_PORT_ENABLE_COMPLETE;
> fw_event->ioc = ioc;
> _scsih_fw_event_add(ioc, fw_event);
> + fw_event_work_put(fw_event);
> +}
> +
> +static struct fw_event_work *dequeue_next_fw_event(struct MPT2SAS_ADAPTER *ioc)
> +{
> + unsigned long flags;
> + struct fw_event_work *fw_event = NULL;
> +
> + spin_lock_irqsave(&ioc->fw_event_lock, flags);
> + if (!list_empty(&ioc->fw_event_list)) {
> + fw_event = list_first_entry(&ioc->fw_event_list,
> + struct fw_event_work, list);
> + list_del_init(&fw_event->list);
> + }
> + spin_unlock_irqrestore(&ioc->fw_event_lock, flags);
> +
> + return fw_event;
> }
>
> /**
> @@ -2956,17 +3005,25 @@ mpt2sas_port_enable_complete(struct MPT2SAS_ADAPTER *ioc)
> static void
> _scsih_fw_event_cleanup_queue(struct MPT2SAS_ADAPTER *ioc)
> {
> - struct fw_event_work *fw_event, *next;
> + struct fw_event_work *fw_event;
>
> if (list_empty(&ioc->fw_event_list) ||
> !ioc->firmware_event_thread || in_interrupt())
> return;
>
> - list_for_each_entry_safe(fw_event, next, &ioc->fw_event_list, list) {
> - if (cancel_delayed_work_sync(&fw_event->delayed_work)) {
> - _scsih_fw_event_free(ioc, fw_event);
> - continue;
> - }
> + while ((fw_event = dequeue_next_fw_event(ioc))) {
> + /*
> + * Wait on the fw_event to complete. If this returns 1, then
> + * the event was never executed, and we need a put for the
> + * reference the delayed_work had on the fw_event.
> + *
> + * If it did execute, we wait for it to finish, and the put will
> + * happen from _firmware_event_work()
> + */
> + if (cancel_delayed_work_sync(&fw_event->delayed_work))
> + fw_event_work_put(fw_event);
> +
> + fw_event_work_put(fw_event);
> }
> }
>
> @@ -4447,13 +4504,14 @@ _scsih_send_event_to_turn_on_pfa_led(struct MPT2SAS_ADAPTER *ioc, u16 handle)
> {
> struct fw_event_work *fw_event;
>
> - fw_event = kzalloc(sizeof(struct fw_event_work), GFP_ATOMIC);
> + fw_event = alloc_fw_event_work(0);
> if (!fw_event)
> return;
> fw_event->event = MPT2SAS_TURN_ON_PFA_LED;
> fw_event->device_handle = handle;
> fw_event->ioc = ioc;
> _scsih_fw_event_add(ioc, fw_event);
> + fw_event_work_put(fw_event);
> }
>
> /**
> @@ -7554,17 +7612,27 @@ _firmware_event_work(struct work_struct *work)
> struct fw_event_work, delayed_work.work);
> struct MPT2SAS_ADAPTER *ioc = fw_event->ioc;
>
> + _scsih_fw_event_del_from_list(ioc, fw_event);
> +
> /* the queue is being flushed so ignore this event */
> - if (ioc->remove_host ||
> - ioc->pci_error_recovery) {
> - _scsih_fw_event_free(ioc, fw_event);
> + if (ioc->remove_host || ioc->pci_error_recovery) {
> + fw_event_work_put(fw_event);
> return;
> }
>
> switch (fw_event->event) {
> case MPT2SAS_REMOVE_UNRESPONDING_DEVICES:
> - while (scsi_host_in_recovery(ioc->shost) || ioc->shost_recovery)
> + while (scsi_host_in_recovery(ioc->shost) ||
> + ioc->shost_recovery) {
> + /*
> + * If we're unloading, bail. Otherwise, this can become
> + * an infinite loop.
> + */
> + if (ioc->remove_host)
> + goto out;
> +
> ssleep(1);
> + }
> _scsih_remove_unresponding_sas_devices(ioc);
> _scsih_scan_for_devices_after_reset(ioc);
> break;
> @@ -7613,7 +7681,8 @@ _firmware_event_work(struct work_struct *work)
> _scsih_sas_ir_operation_status_event(ioc, fw_event);
> break;
> }
> - _scsih_fw_event_free(ioc, fw_event);
> +out:
> + fw_event_work_put(fw_event);
> }
>
> /**
> @@ -7751,7 +7820,7 @@ mpt2sas_scsih_event_callback(struct MPT2SAS_ADAPTER *ioc, u8 msix_index,
> }
>
> sz = le16_to_cpu(mpi_reply->EventDataLength) * 4;
> - fw_event = kzalloc(sizeof(*fw_event) + sz, GFP_ATOMIC);
> + fw_event = alloc_fw_event_work(sz);
> if (!fw_event) {
> printk(MPT2SAS_ERR_FMT "failure at %s:%d/%s()!\n",
> ioc->name, __FILE__, __LINE__, __func__);
> @@ -7764,6 +7833,7 @@ mpt2sas_scsih_event_callback(struct MPT2SAS_ADAPTER *ioc, u8 msix_index,
> fw_event->VP_ID = mpi_reply->VP_ID;
> fw_event->event = event;
> _scsih_fw_event_add(ioc, fw_event);
> + fw_event_work_put(fw_event);
> return;
> }
>
> --
> 2.5.0
>


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