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| Started by | "Huang, Ying" <ying.huang@intel.com> |
|---|---|
| First post | 2017-03-20 07:30 +0100 |
| Last post | 2017-03-21 21:50 +0100 |
| Articles | 2 — 2 participants |
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[PATCH] mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() "Huang, Ying" <ying.huang@intel.com> - 2017-03-20 07:30 +0100
Re: [PATCH] mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() Tim Chen <tim.c.chen@linux.intel.com> - 2017-03-21 21:50 +0100
| From | "Huang, Ying" <ying.huang@intel.com> |
|---|---|
| Date | 2017-03-20 07:30 +0100 |
| Subject | [PATCH] mm, swap: Remove WARN_ON_ONCE() in free_swap_slot() |
| Message-ID | <tmYZj-HQ-1@gated-at.bofh.it> |
From: Huang Ying <ying.huang@intel.com>
Before commit 452b94b8c8c7 ("mm/swap: don't BUG_ON() due to
uninitialized swap slot cache"), the following bug is reported,
------------[ cut here ]------------
kernel BUG at mm/swap_slots.c:270!
invalid opcode: 0000 [#1] SMP
CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
Hardware name: System manufacturer System Product Name/Z170-K, BIOS
1803 05/06/2016
RIP: 0010:free_swap_slot+0xba/0xd0
Call Trace:
swap_free+0x36/0x40
do_swap_page+0x360/0x6d0
__handle_mm_fault+0x880/0x1080
handle_mm_fault+0xd0/0x240
__do_page_fault+0x232/0x4d0
do_page_fault+0x20/0x70
page_fault+0x22/0x30
---[ end trace aefc9ede53e0ab21 ]---
This is raised by the BUG_ON(!swap_slot_cache_initialized) in
free_swap_slot(). This is incorrect, because even if the swap slots
cache fails to be initialized, the swap should operate properly
without the swap slots cache. And the use_swap_slot_cache check later
in the function will protect the uninitialized swap slots cache case.
In commit 452b94b8c8c7, the BUG_ON() is replaced by WARN_ON_ONCE().
In the patch, the WARN_ON_ONCE() is removed too.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
---
mm/swap_slots.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index 7ebb23836f68..b1ccb58ad397 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -267,8 +267,6 @@ int free_swap_slot(swp_entry_t entry)
{
struct swap_slots_cache *cache;
- WARN_ON_ONCE(!swap_slot_cache_initialized);
-
cache = &get_cpu_var(swp_slots);
if (use_swap_slot_cache && cache->slots_ret) {
spin_lock_irq(&cache->free_lock);
--
2.11.0
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| From | Tim Chen <tim.c.chen@linux.intel.com> |
|---|---|
| Date | 2017-03-21 21:50 +0100 |
| Message-ID | <tnyT8-8vM-11@gated-at.bofh.it> |
| In reply to | #1604196 |
On Mon, 2017-03-20 at 14:26 +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> Before commit 452b94b8c8c7 ("mm/swap: don't BUG_ON() due to
> uninitialized swap slot cache"), the following bug is reported,
>
> ------------[ cut here ]------------
> kernel BUG at mm/swap_slots.c:270!
> invalid opcode: 0000 [#1] SMP
> CPU: 5 PID: 1745 Comm: (sd-pam) Not tainted 4.11.0-rc1-00243-g24c534bb161b #1
> Hardware name: System manufacturer System Product Name/Z170-K, BIOS
> 1803 05/06/2016
> RIP: 0010:free_swap_slot+0xba/0xd0
> Call Trace:
> swap_free+0x36/0x40
> do_swap_page+0x360/0x6d0
> __handle_mm_fault+0x880/0x1080
> handle_mm_fault+0xd0/0x240
> __do_page_fault+0x232/0x4d0
> do_page_fault+0x20/0x70
> page_fault+0x22/0x30
> ---[ end trace aefc9ede53e0ab21 ]---
>
> This is raised by the BUG_ON(!swap_slot_cache_initialized) in
> free_swap_slot(). This is incorrect, because even if the swap slots
> cache fails to be initialized, the swap should operate properly
> without the swap slots cache. And the use_swap_slot_cache check later
> in the function will protect the uninitialized swap slots cache case.
>
> In commit 452b94b8c8c7, the BUG_ON() is replaced by WARN_ON_ONCE().
> In the patch, the WARN_ON_ONCE() is removed too.
>
This replaces my previous patch to replace the BUG_ON.
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Tim Chen <tim.c.chen@linux.intel.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> ---
> mm/swap_slots.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/mm/swap_slots.c b/mm/swap_slots.c
> index 7ebb23836f68..b1ccb58ad397 100644
> --- a/mm/swap_slots.c
> +++ b/mm/swap_slots.c
> @@ -267,8 +267,6 @@ int free_swap_slot(swp_entry_t entry)
> {
> struct swap_slots_cache *cache;
>
> - WARN_ON_ONCE(!swap_slot_cache_initialized);
> -
> cache = &get_cpu_var(swp_slots);
> if (use_swap_slot_cache && cache->slots_ret) {
> spin_lock_irq(&cache->free_lock);
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