tree 4fbf9c7677acb03c23d05faba1a4b0bcfb6702b4
parent 1d589bb16b825b3a7b4edd34d997f1f1f953033d
author Nikanth Karthikesan <knikanth@novell.com> 1244663826 -0700
committer Jens Axboe <jens.axboe@oracle.com> 1244668035 +0200

block: prevent possible io_context->refcount overflow

Currently io_context has an atomic_t(32-bit) as refcount.  In the case of
cfq, for each device against whcih a task does I/O, a reference to the
io_context would be taken.  And when there are multiple process sharing
io_contexts(CLONE_IO) would also have a reference to the same io_context.

Theoretically the possible maximum number of processes sharing the same
io_context + the number of disks/cfq_data referring to the same io_context
can overflow the 32-bit counter on a very high-end machine.

Even though it is an improbable case, let us make it atomic_long_t.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>