[SCSI] mpt2sas: Improvement were made to better protect the sas_device,...
[SCSI] mpt2sas: Improvement were made to better protect the sas_device, raid_device, and expander_device lists There were possible race conditions surrounding reading an object from the link list while from another context in the driver was removing it. The nature of this enhancement is to rearrange locking so the link lists are better protected. Change set: (1) numerous routines were rearranged so spin locks are held through the entire time a link list object is being read from or written to. (2) added new routines for object deletion from link list. Thus ensuring lock was held during the deletion of the link list object, then and memory for object freed outside the lock. The memory was freed outside the lock so driver had access to device object info which was required for notifying the scsi mid layer that a device was getting deleted. (3) added the ioc->blocking_handles parameter. This is a bitmask used to identify which devices need blocking when there is device loss. This was introduced so that lock can be held for the entire time traversing the link list objects, and the bitmask was set to indicate which device handles need blocking. Oustide the lock the ioc->blocking_handles bitmask is traversed, with the respective device handle the scsi mid layer is called for moving devices into blocking state. Signed-off-by: NNagalakshmi Nandigama <nagalakshmi.nandigama@lsi.com> Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>
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