[openib-general] SRP [PATCH 0/4] Kernel support for removal and restoration of target

[Ishai Rabinovitz]

Hi Roland,

I'm sending 4 patches that implement kernel support for removal and restoration
of a target (will be used by ibsrpdm).

Some comments about them

1) The first patch splits reconnect to 2 two functions: _srp_remove_target 
   and _srp_restore_target. _srp_remove_target uses the functions I sent in 
   previous patch (Misc cleanups in ib_srp). If you want I can resend this 
   patch without using the previous patch (But then there will be a problem 
   with the previous patch :(  ).

2) These patches implement the following behavior: When someone writes the
   string "remove" to /sys/class/scsi_host/host?/remove_target the corresponding
   target goes to a DISCONNECTED state (After closing the cm, and reset all 
   pending requests).
   Now when the scsi performs queuecommand to this host a SCSI_MLQUEUE_HOST_BUSY
   is returned. These causes the scsi layer to wait until the target turns
   to LIVE state. This is very nice if the user that initiated the remove_target
   knows what he is doing and will perform a restore_target later. On the other 
   hand it may be problematic if the target remains DISCONNECTED and user
   applications that try to access this target remain stuck in the kernel (in 
   the scsi layer)
   I've several ideas on how to handle it (have a timeout after which 
   queuecommand will return fail, try to perform a restore_target after a
   timeout, make sure the daemon will run a restore_target after a timeout) 
   but I'm not sure they are the correct thing to do. I'm waiting for
   suggestions.
   In any case I believe we should apply these patches and add solution to
   this problem later.

Please comment.

-- 
Ishai Rabinovitz