On Wed, Jan 18, 2017 at 01:45:55PM +0100, Michal Hocko wrote:
> On Tue 17-01-17 13:42:35, Tim Chen wrote:
> [...]
> > Logic wise, We do allow pre-emption as per cpu ptr cache->slots is
> > protected by the mutex cache->alloc_lock. We switch the
> > inappropriately used this_cpu_ptr to raw_cpu_ptr for per cpu ptr
> > access of cache->slots.
>
> OK, that looks better. I would still appreciate something like the
> following folded in
> diff --git a/include/linux/swap_slots.h b/include/linux/swap_slots.h
> index fb907346c5c6..0afe748453a7 100644
> --- a/include/linux/swap_slots.h
> +++ b/include/linux/swap_slots.h
> @@ -11,6 +11,7 @@
>
> struct swap_slots_cache {
> bool lock_initialized;
> + /* protects slots, nr, cur */
> struct mutex alloc_lock;
> swp_entry_t *slots;
> int nr;
>
I've included here a patch for the comments.
Thanks.
Tim
--->8---
From: Tim Chen <tim.c.c...@linux.intel.com>
Date: Wed, 18 Jan 2017 09:52:28 -0800
Subject: [PATCH] mm/swap: Add comments on locks in swap_slots.h
To: Andrew Morton <a...@linux-foundation.org>
Cc: Ying Huang <ying.hu...@intel.com>, dave.han...@intel.com,
a...@linux.intel.com, aaron...@intel.com, linux...@kvack.org,
linux-kernel@vger.kernel.org, Hugh Dickins <hu...@google.com>, Shaohua Li
<s...@kernel.org>, Minchan Kim <minc...@kernel.org>, Rik van Riel
<r...@redhat.com>, Andrea Arcangeli <aarca...@redhat.com>, Kirill A . Shutemov
<kirill.shute...@linux.intel.com>, Vladimir Davydov <vdavydov....@gmail.com>,
Johannes Weiner <han...@cmpxchg.org>, Michal Hocko <mho...@kernel.org>, Hillf
Danton <hillf...@alibaba-inc.com>, Christian Borntraeger
<borntrae...@de.ibm.com>, Jonathan Corbet <cor...@lwn.net>
Explains what each lock protects in swap_slots_cache structure.
Signed-off-by: Tim Chen <tim.c.c...@linux.intel.com>
---
include/linux/swap_slots.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/swap_slots.h b/include/linux/swap_slots.h
index fb90734..6ef92d1 100644
--- a/include/linux/swap_slots.h
+++ b/include/linux/swap_slots.h
@@ -11,11 +11,11 @@
struct swap_slots_cache {
bool lock_initialized;
- struct mutex alloc_lock;
+ struct mutex alloc_lock; /* protects slots, nr, cur */
swp_entry_t *slots;
int nr;
int cur;
- spinlock_t free_lock;
+ spinlock_t free_lock; /* protects slots_ret, n_ret */
swp_entry_t *slots_ret;
int n_ret;
};
--
2.5.5
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