Re: [PATCH] Separate target visibility from reaped state information

[Bart Van Assche <bart.vanassche@sandisk.com>]

On 02/02/2016 03:46 AM, James Bottomley wrote:
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 4f18a85..00bc721 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1272,16 +1272,18 @@ static void __scsi_remove_target(struct scsi_target *starget)
>   void scsi_remove_target(struct device *dev)
>   {
>       struct Scsi_Host *shost = dev_to_shost(dev->parent);
> -     struct scsi_target *starget;
> +     struct scsi_target *starget, *last_target = NULL;
>       unsigned long flags;
>
>   restart:
>       spin_lock_irqsave(shost->host_lock, flags);
>       list_for_each_entry(starget, &shost->__targets, siblings) {
> -             if (starget->state == STARGET_DEL)
> +             if (starget->state == STARGET_DEL ||
> +                 starget == last_target)
>                       continue;
>               if (starget->dev.parent == dev || &starget->dev == dev) {
>                       kref_get(&starget->reap_ref);
> +                     last_target = starget;
>                       spin_unlock_irqrestore(shost->host_lock, flags);
>                       __scsi_remove_target(starget);
>                       scsi_target_reap(starget);

Hello James,

Do you think it is a robust approach to store the pointer to the last
removed target in the last_target variable ? What if e.g.
scsi_target_reap() frees the memory the last_target pointer points at
and another thread reallocates a scsi_target data structure ? Can that
last data structure have the same address as the contents of the
last_target variable ?

Thanks,

Bart.
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