On Fri, Sep 26 2003, Steven Dake wrote:

Folks,
Thanks Matt and Jens for the debug help on the multipath problem.  I now
have a patch (attached) which solves the problem and makes multipath
work properly.   There are two types of "flags" that are used in a block
io request, bi_flags, and bi_rw.  bi_flags is used for flags to the
block level code, and bi_rw is used for flags to the low level device
drivers.  The code in the multipath driver used the wrong flag in the
wrong field.  In this case, the flag FASTFAIL (value 3) was being set to
the bi_flags field.  FASTFAIL is a hint to the low level driver that it
should try to fail out quickly.  Unfortunately, the value 3 is also
BIO_SEG_VALID, which is a flag to the block subsystem that the segments
shouldn't be recalculated.  The result was that the wrong field was set,
telling the block layer not to recalculate the segments resulting in
phys and hw segments of 0.  Not good.

Neil can you send upstream ?

Auch good catch! I'm sorry to say this is actually my fault...

-- 
Jens Axboe