smartctl likes to read SMART data into 512 byte buffers which it allocates on the stack.  While this _should_ work just fine, I have found that sometimes, when using SATA over SAS (-d sat) with an MPT Fusion HBA, smartctl's buffer gets broken into 2 Scatter Gather Elements (probably because the 512 byte buffer stradles a page boundary).  Sometimes, only the first of these gets filled before the mpt driver records a timeout and subsequently resets the SAS bus.

I have not fully diagnosed the problem or had time to write a sample code'let that can reproduce it.  But in the mean time, this patch moves the data buffer from the stack to the heap where it will be aligned to avoid a page boundary.

Hopefully I will have time to diagnose the real problem and either fix it (if it's in the driver) or send in a bug report to LSI (if it's in the MPT controller).

thanx,
brad

Fix: Attached is a patch to the port that adds a patch that makes shure the data buffers used to read smart attributes and logs do not straddle page boundaries.

Patch attached with submission follows:
How-To-Repeat: pray.  Then on a 64bit system, with an 8gig LSI MPT SAS controler
           Mpi Version 1.5.20.0
             FWVersion 1.28.0.0
or           FWVersion 1.28.2.0
connected to a SATA drive, turn on all available debugging in CAM and the MPT driver.

run smartctl -d sat -r ioctl -a /dev/da<foo>

sometimes, if you're 'lucky', you'll see a bus reset, and smartcl will fail to get some of it's SMART data.