[PATCH AUTOSEL for 4.15 067/124] staging: lustre: disable preempt while sampling processor id.

[Sasha Levin]

From: NeilBrown <ne...@suse.com>

[ Upstream commit dbeccabf5294e80f7cc9ee566746c42211bed736 ]

Calling smp_processor_id() without disabling preemption
triggers a warning (if CONFIG_DEBUG_PREEMPT).
I think the result of cfs_cpt_current() is only used as a hint for
load balancing, rather than as a precise and stable indicator of
the current CPU.  So it doesn't need to be called with
preemption disabled.

So disable preemption inside cfs_cpt_current() to silence the warning.

Signed-off-by: NeilBrown <ne...@suse.com>
Reviewed-by: Andreas Dilger <andreas.dil...@intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c 
b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
index 51823ce71773..a013f7eb208f 100644
--- a/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
+++ b/drivers/staging/lustre/lnet/libcfs/linux/linux-cpu.c
@@ -529,19 +529,20 @@ EXPORT_SYMBOL(cfs_cpt_spread_node);
 int
 cfs_cpt_current(struct cfs_cpt_table *cptab, int remap)
 {
-       int cpu = smp_processor_id();
-       int cpt = cptab->ctb_cpu2cpt[cpu];
+       int cpu;
+       int cpt;
 
-       if (cpt < 0) {
-               if (!remap)
-                       return cpt;
+       preempt_disable();
+       cpu = smp_processor_id();
+       cpt = cptab->ctb_cpu2cpt[cpu];
 
+       if (cpt < 0 && remap) {
                /* don't return negative value for safety of upper layer,
                 * instead we shadow the unknown cpu to a valid partition ID
                 */
                cpt = cpu % cptab->ctb_nparts;
        }
-
+       preempt_enable();
        return cpt;
 }
 EXPORT_SYMBOL(cfs_cpt_current);
-- 
2.14.1