[PATCH] net: rds: fix per-cpu helper usage

[Gerald Schaefer]

commit ae4b46e9d "net: rds: use this_cpu_* per-cpu helper" broke per-cpu
handling for rds. chpfirst is the result of __this_cpu_read(), so it is
an absolute pointer and not __percpu. Therefore, __this_cpu_write()
should not operate on chpfirst, but rather on cache->percpu->first, just
like __this_cpu_read() did before.

Cc: <sta...@vger.kernel.org> # 3.8+
Signed-off-byd Gerald Schaefer <gerald....@de.ibm.com>
---
net/rds/ib_recv.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c
index 8eb9501..b7ebe23 100644
--- a/net/rds/ib_recv.c
+++ b/net/rds/ib_recv.c
@@ -421,8 +421,7 @@ static void rds_ib_recv_cache_put(struct list_head *new_item,
struct rds_ib_refill_cache *cache)
{
unsigned long flags;
- struct list_head *old;
- struct list_head __percpu *chpfirst;
+ struct list_head *old, *chpfirst;

local_irq_save(flags);

@@ -432,7 +431,7 @@ static void rds_ib_recv_cache_put(struct list_head *new_item,
else /* put on front */
list_add_tail(new_item, chpfirst);

- __this_cpu_write(chpfirst, new_item);
+ __this_cpu_write(cache->percpu->first, new_item);
__this_cpu_inc(cache->percpu->count);

if (__this_cpu_read(cache->percpu->count) < RDS_IB_RECYCLE_BATCH_COUNT)
@@ -452,7 +451,7 @@ static void rds_ib_recv_cache_put(struct list_head *new_item,
} while (old);


- __this_cpu_write(chpfirst, NULL);
+ __this_cpu_write(cache->percpu->first, NULL);
__this_cpu_write(cache->percpu->count, 0);
end:
local_irq_restore(flags);
--
1.8.4.5

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[David Miller]

From: Gerald Schaefer <gerald....@de.ibm.com>
Date: Thu, 16 Jan 2014 16:54:48 +0100

> commit ae4b46e9d "net: rds: use this_cpu_* per-cpu helper" broke per-cpu
> handling for rds. chpfirst is the result of __this_cpu_read(), so it is
> an absolute pointer and not __percpu. Therefore, __this_cpu_write()
> should not operate on chpfirst, but rather on cache->percpu->first, just
> like __this_cpu_read() did before.
>
> Cc: <sta...@vger.kernel.org> # 3.8+
> Signed-off-byd Gerald Schaefer <gerald....@de.ibm.com>

Applied and queued up for -stable, thanks.