block: Range check cpu in blk_cpu_to_group
While testing CPU DLPAR, the following problem was discovered.
We were DLPAR removing the first CPU, which in this case was
logical CPUs 0-3. CPUs 0-2 were already marked offline and
we were in the process of offlining CPU 3. After marking
the CPU inactive and offline in cpu_disable, but before the
cpu was completely idle (cpu_die), we ended up in __make_request
on CPU 3. There we looked at the topology map to see which CPU
to complete the I/O on and found no CPUs in the cpu_sibling_map.
This resulted in the block layer setting the completion cpu
to be NR_CPUS, which then caused an oops when we tried to
complete the I/O.
Fix this by sanity checking the value we return from blk_cpu_to_group
to be a valid cpu value.
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk.h b/block/blk.h
index 6e7dc87..d6b911a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -142,14 +142,18 @@
static inline int blk_cpu_to_group(int cpu)
{
+ int group = NR_CPUS;
#ifdef CONFIG_SCHED_MC
const struct cpumask *mask = cpu_coregroup_mask(cpu);
- return cpumask_first(mask);
+ group = cpumask_first(mask);
#elif defined(CONFIG_SCHED_SMT)
- return cpumask_first(topology_thread_cpumask(cpu));
+ group = cpumask_first(topology_thread_cpumask(cpu));
#else
return cpu;
#endif
+ if (likely(group < NR_CPUS))
+ return group;
+ return cpu;
}
/*