* [PATCH] mm: Fix a race during split THP
@ 2020-10-09 7:36 Huang, Ying
2020-10-09 7:47 ` Huang, Ying
` (3 more replies)
0 siblings, 4 replies; 8+ messages in thread
From: Huang, Ying @ 2020-10-09 7:36 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Huang Ying, Rafael Aquini, Hugh Dickins,
Kirill A . Shutemov, Andrea Arcangeli
From: Huang Ying <ying.huang@intel.com>
It is reported that the following bug is triggered if the HDD is used as swap
device,
[ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007
[ 5758.165331] #PF: supervisor write access in kernel mode
[ 5758.171161] #PF: error_code(0x0002) - not-present page
[ 5758.176894] PGD 0 P4D 0
[ 5758.179721] Oops: 0002 [#1] SMP PTI
[ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1
[ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013
[ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60
[ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f
[ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246
[ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000
[ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217
[ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000
[ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000
[ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040
[ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000
[ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0
[ 5758.303538] Call Trace:
[ 5758.306273] split_huge_page_to_list+0x88b/0x950
[ 5758.311433] deferred_split_scan+0x1ca/0x310
[ 5758.316202] do_shrink_slab+0x12c/0x2a0
[ 5758.320491] shrink_slab+0x20f/0x2c0
[ 5758.324482] shrink_node+0x240/0x6c0
[ 5758.328469] balance_pgdat+0x2d1/0x550
[ 5758.332652] kswapd+0x201/0x3c0
[ 5758.336157] ? finish_wait+0x80/0x80
[ 5758.340147] ? balance_pgdat+0x550/0x550
[ 5758.344525] kthread+0x114/0x130
[ 5758.348126] ? kthread_park+0x80/0x80
[ 5758.352214] ret_from_fork+0x22/0x30
[ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod
[ 5758.412673] CR2: 0000000000000007
[ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020
After further digging it's found that the following race condition exists in the
original implementation,
CPU1 CPU2
---- ----
deferred_split_scan()
split_huge_page(page) /* page isn't compound head */
split_huge_page_to_list(page, NULL)
__split_huge_page(page, )
ClearPageCompound(head)
/* unlock all subpages except page (not head) */
add_to_swap(head) /* not THP */
get_swap_page(head)
add_to_swap_cache(head, )
SetPageSwapCache(head)
if PageSwapCache(head)
split_swap_cluster(/* swap entry of head */)
/* Deref sis->cluster_info: NULL accessing! */
So, in split_huge_page_to_list(), PageSwapCache() is called for the already
split and unlocked "head", which may be added to swap cache in another CPU. So
split_swap_cluster() may be called wrongly.
To fix the race, the call to split_swap_cluster() is moved to
__split_huge_page() before all subpages are unlocked. So that the
PageSwapCache() is stable.
Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out")
Reported-and-tested-by: Rafael Aquini <aquini@redhat.com>
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
---
mm/huge_memory.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index cba3812a5c3e..87b0389673dd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2478,6 +2478,12 @@ static void __split_huge_page(struct page *page, struct list_head *list,
remap_page(head, nr);
+ if (PageSwapCache(head)) {
+ swp_entry_t entry = { .val = page_private(head) };
+
+ split_swap_cluster(entry);
+ }
+
for (i = 0; i < nr; i++) {
struct page *subpage = head + i;
if (subpage == page)
@@ -2713,12 +2719,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
}
__split_huge_page(page, list, end, flags);
- if (PageSwapCache(head)) {
- swp_entry_t entry = { .val = page_private(head) };
-
- ret = split_swap_cluster(entry);
- } else
- ret = 0;
+ ret = 0;
} else {
if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
pr_alert("total_mapcount: %u, page_count(): %u\n",
--
2.28.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-09 7:36 [PATCH] mm: Fix a race during split THP Huang, Ying
@ 2020-10-09 7:47 ` Huang, Ying
2020-10-09 13:22 ` Kirill A. Shutemov
` (2 subsequent siblings)
3 siblings, 0 replies; 8+ messages in thread
From: Huang, Ying @ 2020-10-09 7:47 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Rafael Aquini, Hugh Dickins,
Kirill A . Shutemov, Andrea Arcangeli
"Huang, Ying" <ying.huang@intel.com> writes:
> From: Huang Ying <ying.huang@intel.com>
>
> It is reported that the following bug is triggered if the HDD is used as swap
> device,
>
> [ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007
> [ 5758.165331] #PF: supervisor write access in kernel mode
> [ 5758.171161] #PF: error_code(0x0002) - not-present page
> [ 5758.176894] PGD 0 P4D 0
> [ 5758.179721] Oops: 0002 [#1] SMP PTI
> [ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1
> [ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013
> [ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60
> [ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f
> [ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246
> [ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000
> [ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217
> [ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000
> [ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000
> [ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040
> [ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000
> [ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0
> [ 5758.303538] Call Trace:
> [ 5758.306273] split_huge_page_to_list+0x88b/0x950
> [ 5758.311433] deferred_split_scan+0x1ca/0x310
> [ 5758.316202] do_shrink_slab+0x12c/0x2a0
> [ 5758.320491] shrink_slab+0x20f/0x2c0
> [ 5758.324482] shrink_node+0x240/0x6c0
> [ 5758.328469] balance_pgdat+0x2d1/0x550
> [ 5758.332652] kswapd+0x201/0x3c0
> [ 5758.336157] ? finish_wait+0x80/0x80
> [ 5758.340147] ? balance_pgdat+0x550/0x550
> [ 5758.344525] kthread+0x114/0x130
> [ 5758.348126] ? kthread_park+0x80/0x80
> [ 5758.352214] ret_from_fork+0x22/0x30
> [ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod
> [ 5758.412673] CR2: 0000000000000007
> [ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020
>
> After further digging it's found that the following race condition exists in the
> original implementation,
>
> CPU1 CPU2
> ---- ----
> deferred_split_scan()
> split_huge_page(page) /* page isn't compound head */
> split_huge_page_to_list(page, NULL)
> __split_huge_page(page, )
> ClearPageCompound(head)
> /* unlock all subpages except page (not head) */
> add_to_swap(head) /* not THP */
> get_swap_page(head)
> add_to_swap_cache(head, )
> SetPageSwapCache(head)
> if PageSwapCache(head)
> split_swap_cluster(/* swap entry of head */)
> /* Deref sis->cluster_info: NULL accessing! */
>
> So, in split_huge_page_to_list(), PageSwapCache() is called for the already
> split and unlocked "head", which may be added to swap cache in another CPU. So
> split_swap_cluster() may be called wrongly.
>
> To fix the race, the call to split_swap_cluster() is moved to
> __split_huge_page() before all subpages are unlocked. So that the
> PageSwapCache() is stable.
>
> Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out")
> Reported-and-tested-by: Rafael Aquini <aquini@redhat.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
Sorry, should have added
Cc: stable@vger.kernel.org
Best Regards,
Huang, Ying
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-09 7:36 [PATCH] mm: Fix a race during split THP Huang, Ying
2020-10-09 7:47 ` Huang, Ying
@ 2020-10-09 13:22 ` Kirill A. Shutemov
2020-10-09 13:27 ` Matthew Wilcox
2020-10-27 10:25 ` Michal Hocko
3 siblings, 0 replies; 8+ messages in thread
From: Kirill A. Shutemov @ 2020-10-09 13:22 UTC (permalink / raw)
To: Huang, Ying
Cc: Andrew Morton, linux-mm, linux-kernel, Rafael Aquini,
Hugh Dickins, Andrea Arcangeli
On Fri, Oct 09, 2020 at 03:36:47PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> It is reported that the following bug is triggered if the HDD is used as swap
> device,
>
> [ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007
> [ 5758.165331] #PF: supervisor write access in kernel mode
> [ 5758.171161] #PF: error_code(0x0002) - not-present page
> [ 5758.176894] PGD 0 P4D 0
> [ 5758.179721] Oops: 0002 [#1] SMP PTI
> [ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1
> [ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013
> [ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60
> [ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f
> [ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246
> [ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000
> [ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217
> [ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000
> [ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000
> [ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040
> [ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000
> [ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0
> [ 5758.303538] Call Trace:
> [ 5758.306273] split_huge_page_to_list+0x88b/0x950
> [ 5758.311433] deferred_split_scan+0x1ca/0x310
> [ 5758.316202] do_shrink_slab+0x12c/0x2a0
> [ 5758.320491] shrink_slab+0x20f/0x2c0
> [ 5758.324482] shrink_node+0x240/0x6c0
> [ 5758.328469] balance_pgdat+0x2d1/0x550
> [ 5758.332652] kswapd+0x201/0x3c0
> [ 5758.336157] ? finish_wait+0x80/0x80
> [ 5758.340147] ? balance_pgdat+0x550/0x550
> [ 5758.344525] kthread+0x114/0x130
> [ 5758.348126] ? kthread_park+0x80/0x80
> [ 5758.352214] ret_from_fork+0x22/0x30
> [ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod
> [ 5758.412673] CR2: 0000000000000007
> [ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020
>
> After further digging it's found that the following race condition exists in the
> original implementation,
>
> CPU1 CPU2
> ---- ----
> deferred_split_scan()
> split_huge_page(page) /* page isn't compound head */
> split_huge_page_to_list(page, NULL)
> __split_huge_page(page, )
> ClearPageCompound(head)
> /* unlock all subpages except page (not head) */
> add_to_swap(head) /* not THP */
> get_swap_page(head)
> add_to_swap_cache(head, )
> SetPageSwapCache(head)
> if PageSwapCache(head)
> split_swap_cluster(/* swap entry of head */)
> /* Deref sis->cluster_info: NULL accessing! */
>
> So, in split_huge_page_to_list(), PageSwapCache() is called for the already
> split and unlocked "head", which may be added to swap cache in another CPU. So
> split_swap_cluster() may be called wrongly.
>
> To fix the race, the call to split_swap_cluster() is moved to
> __split_huge_page() before all subpages are unlocked. So that the
> PageSwapCache() is stable.
>
> Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out")
> Reported-and-tested-by: Rafael Aquini <aquini@redhat.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
Looks good to me.
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
--
Kirill A. Shutemov
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-09 7:36 [PATCH] mm: Fix a race during split THP Huang, Ying
2020-10-09 7:47 ` Huang, Ying
2020-10-09 13:22 ` Kirill A. Shutemov
@ 2020-10-09 13:27 ` Matthew Wilcox
2020-10-10 0:26 ` Huang, Ying
2020-10-27 10:25 ` Michal Hocko
3 siblings, 1 reply; 8+ messages in thread
From: Matthew Wilcox @ 2020-10-09 13:27 UTC (permalink / raw)
To: Huang, Ying
Cc: Andrew Morton, linux-mm, linux-kernel, Rafael Aquini,
Hugh Dickins, Kirill A . Shutemov, Andrea Arcangeli
On Fri, Oct 09, 2020 at 03:36:47PM +0800, Huang, Ying wrote:
> + if (PageSwapCache(head)) {
> + swp_entry_t entry = { .val = page_private(head) };
> +
> + split_swap_cluster(entry);
> + }
...
> - if (PageSwapCache(head)) {
> - swp_entry_t entry = { .val = page_private(head) };
> -
> - ret = split_swap_cluster(entry);
Are we sure split_swap_cluster() can't fail? Or if it does fail, it's
OK to continue with the split and not report the error?
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-09 13:27 ` Matthew Wilcox
@ 2020-10-10 0:26 ` Huang, Ying
0 siblings, 0 replies; 8+ messages in thread
From: Huang, Ying @ 2020-10-10 0:26 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Andrew Morton, linux-mm, linux-kernel, Rafael Aquini,
Hugh Dickins, Kirill A . Shutemov, Andrea Arcangeli
Matthew Wilcox <willy@infradead.org> writes:
> On Fri, Oct 09, 2020 at 03:36:47PM +0800, Huang, Ying wrote:
>> + if (PageSwapCache(head)) {
>> + swp_entry_t entry = { .val = page_private(head) };
>> +
>> + split_swap_cluster(entry);
>> + }
> ...
>> - if (PageSwapCache(head)) {
>> - swp_entry_t entry = { .val = page_private(head) };
>> -
>> - ret = split_swap_cluster(entry);
>
> Are we sure split_swap_cluster() can't fail? Or if it does fail, it's
> OK to continue with the split and not report the error?
split_swap_cluster() can only fail for invalid swap entry. Which isn't
expected to happen in this situation.
Best Regards,
Huang, Ying
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-09 7:36 [PATCH] mm: Fix a race during split THP Huang, Ying
` (2 preceding siblings ...)
2020-10-09 13:27 ` Matthew Wilcox
@ 2020-10-27 10:25 ` Michal Hocko
2020-10-28 22:43 ` Andrew Morton
3 siblings, 1 reply; 8+ messages in thread
From: Michal Hocko @ 2020-10-27 10:25 UTC (permalink / raw)
To: Huang, Ying
Cc: Andrew Morton, linux-mm, linux-kernel, Rafael Aquini,
Hugh Dickins, Kirill A . Shutemov, Andrea Arcangeli,
Matthew Wilcox
Hi,
I have noticed this fix and I do not see it in the mmotm tree.
Is there anything blocking this patch or it simply fall through cracks?
On Fri 09-10-20 15:36:47, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
>
> It is reported that the following bug is triggered if the HDD is used as swap
> device,
>
> [ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007
> [ 5758.165331] #PF: supervisor write access in kernel mode
> [ 5758.171161] #PF: error_code(0x0002) - not-present page
> [ 5758.176894] PGD 0 P4D 0
> [ 5758.179721] Oops: 0002 [#1] SMP PTI
> [ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1
> [ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013
> [ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60
> [ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f
> [ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246
> [ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000
> [ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217
> [ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000
> [ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000
> [ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040
> [ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000
> [ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0
> [ 5758.303538] Call Trace:
> [ 5758.306273] split_huge_page_to_list+0x88b/0x950
> [ 5758.311433] deferred_split_scan+0x1ca/0x310
> [ 5758.316202] do_shrink_slab+0x12c/0x2a0
> [ 5758.320491] shrink_slab+0x20f/0x2c0
> [ 5758.324482] shrink_node+0x240/0x6c0
> [ 5758.328469] balance_pgdat+0x2d1/0x550
> [ 5758.332652] kswapd+0x201/0x3c0
> [ 5758.336157] ? finish_wait+0x80/0x80
> [ 5758.340147] ? balance_pgdat+0x550/0x550
> [ 5758.344525] kthread+0x114/0x130
> [ 5758.348126] ? kthread_park+0x80/0x80
> [ 5758.352214] ret_from_fork+0x22/0x30
> [ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod
> [ 5758.412673] CR2: 0000000000000007
> [ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020
>
> After further digging it's found that the following race condition exists in the
> original implementation,
>
> CPU1 CPU2
> ---- ----
> deferred_split_scan()
> split_huge_page(page) /* page isn't compound head */
> split_huge_page_to_list(page, NULL)
> __split_huge_page(page, )
> ClearPageCompound(head)
> /* unlock all subpages except page (not head) */
> add_to_swap(head) /* not THP */
> get_swap_page(head)
> add_to_swap_cache(head, )
> SetPageSwapCache(head)
> if PageSwapCache(head)
> split_swap_cluster(/* swap entry of head */)
> /* Deref sis->cluster_info: NULL accessing! */
>
> So, in split_huge_page_to_list(), PageSwapCache() is called for the already
> split and unlocked "head", which may be added to swap cache in another CPU. So
> split_swap_cluster() may be called wrongly.
>
> To fix the race, the call to split_swap_cluster() is moved to
> __split_huge_page() before all subpages are unlocked. So that the
> PageSwapCache() is stable.
>
> Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out")
> Reported-and-tested-by: Rafael Aquini <aquini@redhat.com>
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> ---
> mm/huge_memory.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index cba3812a5c3e..87b0389673dd 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2478,6 +2478,12 @@ static void __split_huge_page(struct page *page, struct list_head *list,
>
> remap_page(head, nr);
>
> + if (PageSwapCache(head)) {
> + swp_entry_t entry = { .val = page_private(head) };
> +
> + split_swap_cluster(entry);
> + }
> +
> for (i = 0; i < nr; i++) {
> struct page *subpage = head + i;
> if (subpage == page)
> @@ -2713,12 +2719,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
> }
>
> __split_huge_page(page, list, end, flags);
> - if (PageSwapCache(head)) {
> - swp_entry_t entry = { .val = page_private(head) };
> -
> - ret = split_swap_cluster(entry);
> - } else
> - ret = 0;
> + ret = 0;
> } else {
> if (IS_ENABLED(CONFIG_DEBUG_VM) && mapcount) {
> pr_alert("total_mapcount: %u, page_count(): %u\n",
> --
> 2.28.0
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-27 10:25 ` Michal Hocko
@ 2020-10-28 22:43 ` Andrew Morton
2020-10-29 9:46 ` Michal Hocko
0 siblings, 1 reply; 8+ messages in thread
From: Andrew Morton @ 2020-10-28 22:43 UTC (permalink / raw)
To: Michal Hocko
Cc: Huang, Ying, linux-mm, linux-kernel, Rafael Aquini, Hugh Dickins,
Kirill A . Shutemov, Andrea Arcangeli, Matthew Wilcox
On Tue, 27 Oct 2020 11:25:19 +0100 Michal Hocko <mhocko@suse.com> wrote:
> I have noticed this fix and I do not see it in the mmotm tree.
> Is there anything blocking this patch or it simply fall through cracks?
It's merged into mainline. Perhaps the grammatical fixlet in
the title tricked you...
commit c4f9c701f9b44299e6adbc58d1a4bb2c40383494
Author: Huang Ying <ying.huang@intel.com>
AuthorDate: Thu Oct 15 20:06:07 2020 -0700
Commit: Linus Torvalds <torvalds@linux-foundation.org>
CommitDate: Fri Oct 16 11:11:15 2020 -0700
mm: fix a race during THP splitting
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] mm: Fix a race during split THP
2020-10-28 22:43 ` Andrew Morton
@ 2020-10-29 9:46 ` Michal Hocko
0 siblings, 0 replies; 8+ messages in thread
From: Michal Hocko @ 2020-10-29 9:46 UTC (permalink / raw)
To: Andrew Morton
Cc: Huang, Ying, linux-mm, linux-kernel, Rafael Aquini, Hugh Dickins,
Kirill A . Shutemov, Andrea Arcangeli, Matthew Wilcox
On Wed 28-10-20 15:43:46, Andrew Morton wrote:
> On Tue, 27 Oct 2020 11:25:19 +0100 Michal Hocko <mhocko@suse.com> wrote:
>
> > I have noticed this fix and I do not see it in the mmotm tree.
> > Is there anything blocking this patch or it simply fall through cracks?
>
> It's merged into mainline. Perhaps the grammatical fixlet in
> the title tricked you...
>
> commit c4f9c701f9b44299e6adbc58d1a4bb2c40383494
> Author: Huang Ying <ying.huang@intel.com>
> AuthorDate: Thu Oct 15 20:06:07 2020 -0700
> Commit: Linus Torvalds <torvalds@linux-foundation.org>
> CommitDate: Fri Oct 16 11:11:15 2020 -0700
>
> mm: fix a race during THP splitting
Thanks! I was pretty sure I've checked for the acutal code but myabe I
was just looking incorrectly. Thanks for the clarification!
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-10-29 9:46 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-10-09 7:36 [PATCH] mm: Fix a race during split THP Huang, Ying
2020-10-09 7:47 ` Huang, Ying
2020-10-09 13:22 ` Kirill A. Shutemov
2020-10-09 13:27 ` Matthew Wilcox
2020-10-10 0:26 ` Huang, Ying
2020-10-27 10:25 ` Michal Hocko
2020-10-28 22:43 ` Andrew Morton
2020-10-29 9:46 ` Michal Hocko
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