* kmemleak scan crash due to invalid PFNs
@ 2019-01-17 17:36 Qian Cai
2019-01-17 18:50 ` Oscar Salvador
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: Qian Cai @ 2019-01-17 17:36 UTC (permalink / raw)
To: osalvador, Catalin Marinas, Andrew Morton; +Cc: Linux-MM, linux kernel
On an arm64 ThunderX2 server, the first kmemleak scan would crash with
CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is not directly
mapped. Hence, the page->flags is not initialized.
Reverted 9f1eb38e0e113 (mm, kmemleak: little optimization while scanning) fixed
the problem.
[ 102.195320] Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000006
[ 102.204113] Mem abort info:
[ 102.206921] ESR = 0x96000005
[ 102.209997] Exception class = DABT (current EL), IL = 32 bits
[ 102.215926] SET = 0, FnV = 0
[ 102.218993] EA = 0, S1PTW = 0
[ 102.222150] Data abort info:
[ 102.225047] ISV = 0, ISS = 0x00000005
[ 102.228887] CM = 0, WnR = 0
[ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
[ 102.238572] [0000000000000006] pgd=0000000000000000, pud=0000000000000000
[ 102.245448] Internal error: Oops: 96000005 [#1] SMP
[ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
[ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
[ 102.280409] pc : page_mapping+0x24/0x144
[ 102.280415] lr : __dump_page+0x34/0x3dc
[ 102.292923] sp : ffff00003a5cfd10
[ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
[ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
[ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
[ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
[ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
[ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
[ 102.328049] x17: 0000000000000000 x16: 0000000000000000
[ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
[ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
[ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
[ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
[ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
[ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
[ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
[ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
[ 102.375782] Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____))
[ 102.382648] Call trace:
[ 102.385091] page_mapping+0x24/0x144
[ 102.388659] __dump_page+0x34/0x3dc
[ 102.392140] dump_page+0x28/0x4c
[ 102.395363] kmemleak_scan+0x4ac/0x680
[ 102.399106] kmemleak_scan_thread+0xb4/0xdc
[ 102.403285] kthread+0x12c/0x13c
[ 102.406509] ret_from_fork+0x10/0x18
[ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
[ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
[ 102.420966] Kernel panic - not syncing: Fatal exception
[ 102.426293] SMP: stopping secondary CPUs
[ 102.431830] Kernel Offset: disabled
[ 102.435311] CPU features: 0x002,20000c38
[ 102.439223] Memory Limit: none
[ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: kmemleak scan crash due to invalid PFNs
@ 2019-01-17 18:50 ` Oscar Salvador
0 siblings, 0 replies; 11+ messages in thread
From: Oscar Salvador @ 2019-01-17 18:50 UTC (permalink / raw)
To: Qian Cai
Cc: Oscar Salvador, Catalin Marinas, Andrew Morton, Linux-MM, linux kernel
[-- Attachment #1: Type: text/plain, Size: 3083 bytes --]
On Thu, 17 Jan 2019, 18:36 Qian Cai <cai@lca.pw wrote:
> On an arm64 ThunderX2 server, the first kmemleak scan would crash with
> CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is not
> directly
> mapped. Hence, the page->flags is not initialized.
>
> Reverted 9f1eb38e0e113 (mm, kmemleak: little optimization while scanning)
> fixed
> the problem.
>
Thanks for reporting it.
I will take a look later.
> [ 102.195320] Unable to handle kernel NULL pointer dereference at virtual
> address 0000000000000006
> [ 102.204113] Mem abort info:
> [ 102.206921] ESR = 0x96000005
> [ 102.209997] Exception class = DABT (current EL), IL = 32 bits
> [ 102.215926] SET = 0, FnV = 0
> [ 102.218993] EA = 0, S1PTW = 0
> [ 102.222150] Data abort info:
> [ 102.225047] ISV = 0, ISS = 0x00000005
> [ 102.228887] CM = 0, WnR = 0
> [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
> [ 102.238572] [0000000000000006] pgd=0000000000000000,
> pud=0000000000000000
> [ 102.245448] Internal error: Oops: 96000005 [#1] SMP
> [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
> [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
> [ 102.280409] pc : page_mapping+0x24/0x144
> [ 102.280415] lr : __dump_page+0x34/0x3dc
> [ 102.292923] sp : ffff00003a5cfd10
> [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
> [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
> [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
> [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
> [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
> [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
> [ 102.328049] x17: 0000000000000000 x16: 0000000000000000
> [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
> [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
> [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
> [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
> [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
> [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
> [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
> [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
> [ 102.375782] Process kmemleak (pid: 1408, stack limit =
> 0x(____ptrval____))
> [ 102.382648] Call trace:
> [ 102.385091] page_mapping+0x24/0x144
> [ 102.388659] __dump_page+0x34/0x3dc
> [ 102.392140] dump_page+0x28/0x4c
> [ 102.395363] kmemleak_scan+0x4ac/0x680
> [ 102.399106] kmemleak_scan_thread+0xb4/0xdc
> [ 102.403285] kthread+0x12c/0x13c
> [ 102.406509] ret_from_fork+0x10/0x18
> [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
> [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
> [ 102.420966] Kernel panic - not syncing: Fatal exception
> [ 102.426293] SMP: stopping secondary CPUs
> [ 102.431830] Kernel Offset: disabled
> [ 102.435311] CPU features: 0x002,20000c38
> [ 102.439223] Memory Limit: none
> [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
>
[-- Attachment #2: Type: text/html, Size: 3827 bytes --]
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: kmemleak scan crash due to invalid PFNs
@ 2019-01-17 18:50 ` Oscar Salvador
0 siblings, 0 replies; 11+ messages in thread
From: Oscar Salvador @ 2019-01-17 18:50 UTC (permalink / raw)
To: Qian Cai
Cc: Oscar Salvador, Catalin Marinas, Andrew Morton, Linux-MM, linux kernel
[-- Attachment #1: Type: text/plain, Size: 3083 bytes --]
On Thu, 17 Jan 2019, 18:36 Qian Cai <cai@lca.pw wrote:
> On an arm64 ThunderX2 server, the first kmemleak scan would crash with
> CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is not
> directly
> mapped. Hence, the page->flags is not initialized.
>
> Reverted 9f1eb38e0e113 (mm, kmemleak: little optimization while scanning)
> fixed
> the problem.
>
Thanks for reporting it.
I will take a look later.
> [ 102.195320] Unable to handle kernel NULL pointer dereference at virtual
> address 0000000000000006
> [ 102.204113] Mem abort info:
> [ 102.206921] ESR = 0x96000005
> [ 102.209997] Exception class = DABT (current EL), IL = 32 bits
> [ 102.215926] SET = 0, FnV = 0
> [ 102.218993] EA = 0, S1PTW = 0
> [ 102.222150] Data abort info:
> [ 102.225047] ISV = 0, ISS = 0x00000005
> [ 102.228887] CM = 0, WnR = 0
> [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
> [ 102.238572] [0000000000000006] pgd=0000000000000000,
> pud=0000000000000000
> [ 102.245448] Internal error: Oops: 96000005 [#1] SMP
> [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
> [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
> [ 102.280409] pc : page_mapping+0x24/0x144
> [ 102.280415] lr : __dump_page+0x34/0x3dc
> [ 102.292923] sp : ffff00003a5cfd10
> [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
> [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
> [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
> [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
> [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
> [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
> [ 102.328049] x17: 0000000000000000 x16: 0000000000000000
> [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
> [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
> [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
> [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
> [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
> [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
> [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
> [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
> [ 102.375782] Process kmemleak (pid: 1408, stack limit =
> 0x(____ptrval____))
> [ 102.382648] Call trace:
> [ 102.385091] page_mapping+0x24/0x144
> [ 102.388659] __dump_page+0x34/0x3dc
> [ 102.392140] dump_page+0x28/0x4c
> [ 102.395363] kmemleak_scan+0x4ac/0x680
> [ 102.399106] kmemleak_scan_thread+0xb4/0xdc
> [ 102.403285] kthread+0x12c/0x13c
> [ 102.406509] ret_from_fork+0x10/0x18
> [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
> [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
> [ 102.420966] Kernel panic - not syncing: Fatal exception
> [ 102.426293] SMP: stopping secondary CPUs
> [ 102.431830] Kernel Offset: disabled
> [ 102.435311] CPU features: 0x002,20000c38
> [ 102.439223] Memory Limit: none
> [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
>
[-- Attachment #2: Type: text/html, Size: 3827 bytes --]
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: kmemleak scan crash due to invalid PFNs
2019-01-17 17:36 kmemleak scan crash due to invalid PFNs Qian Cai
2019-01-17 18:50 ` Oscar Salvador
@ 2019-01-17 18:58 ` Oscar Salvador
2019-01-18 2:16 ` [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page() Qian Cai
2 siblings, 0 replies; 11+ messages in thread
From: Oscar Salvador @ 2019-01-17 18:58 UTC (permalink / raw)
To: Qian Cai, Catalin Marinas, Andrew Morton; +Cc: Linux-MM, linux kernel
On Thu, 2019-01-17 at 12:36 -0500, Qian Cai wrote:
> On an arm64 ThunderX2 server, the first kmemleak scan would crash
> with
> CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
> not directly
> mapped. Hence, the page->flags is not initialized.
>
> Reverted 9f1eb38e0e113 (mm, kmemleak: little optimization while
> scanning) fixed
> the problem.
Thanks for reporting this.
I will take a look later.
(sorry for tue dupped mail, html sucks)
>
> [ 102.195320] Unable to handle kernel NULL pointer dereference at
> virtual
> address 0000000000000006
> [ 102.204113] Mem abort info:
> [ 102.206921] ESR = 0x96000005
> [ 102.209997] Exception class = DABT (current EL), IL = 32 bits
> [ 102.215926] SET = 0, FnV = 0
> [ 102.218993] EA = 0, S1PTW = 0
> [ 102.222150] Data abort info:
> [ 102.225047] ISV = 0, ISS = 0x00000005
> [ 102.228887] CM = 0, WnR = 0
> [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp =
> (____ptrval____)
> [ 102.238572] [0000000000000006] pgd=0000000000000000,
> pud=0000000000000000
> [ 102.245448] Internal error: Oops: 96000005 [#1] SMP
> [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-
> rc2+ #8
> [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
> [ 102.280409] pc : page_mapping+0x24/0x144
> [ 102.280415] lr : __dump_page+0x34/0x3dc
> [ 102.292923] sp : ffff00003a5cfd10
> [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
> [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
> [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
> [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
> [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
> [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
> [ 102.328049] x17: 0000000000000000 x16: 0000000000000000
> [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
> [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
> [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
> [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
> [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
> [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
> [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
> [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
> [ 102.375782] Process kmemleak (pid: 1408, stack limit =
> 0x(____ptrval____))
> [ 102.382648] Call trace:
> [ 102.385091] page_mapping+0x24/0x144
> [ 102.388659] __dump_page+0x34/0x3dc
> [ 102.392140] dump_page+0x28/0x4c
> [ 102.395363] kmemleak_scan+0x4ac/0x680
> [ 102.399106] kmemleak_scan_thread+0xb4/0xdc
> [ 102.403285] kthread+0x12c/0x13c
> [ 102.406509] ret_from_fork+0x10/0x18
> [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
> [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
> [ 102.420966] Kernel panic - not syncing: Fatal exception
> [ 102.426293] SMP: stopping secondary CPUs
> [ 102.431830] Kernel Offset: disabled
> [ 102.435311] CPU features: 0x002,20000c38
> [ 102.439223] Memory Limit: none
> [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception
> ]---
--
Oscar Salvador
SUSE L3
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-17 17:36 kmemleak scan crash due to invalid PFNs Qian Cai
2019-01-17 18:50 ` Oscar Salvador
2019-01-17 18:58 ` Oscar Salvador
@ 2019-01-18 2:16 ` Qian Cai
2019-01-21 9:53 ` Michal Hocko
2 siblings, 1 reply; 11+ messages in thread
From: Qian Cai @ 2019-01-18 2:16 UTC (permalink / raw)
To: akpm; +Cc: osalvador, catalin.marinas, mhocko, vbabka, linux-mm, Qian Cai
On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is
uninitialized.
This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little
optimization while scanning") starts to use pfn_to_online_page() instead
of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case,
pfn_to_online_page() does not call memblock_is_map_memory() while
pfn_valid() does.
[1]
[ 102.195320] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006
[ 102.204113] Mem abort info:
[ 102.206921] ESR = 0x96000005
[ 102.209997] Exception class = DABT (current EL), IL = 32 bits
[ 102.215926] SET = 0, FnV = 0
[ 102.218993] EA = 0, S1PTW = 0
[ 102.222150] Data abort info:
[ 102.225047] ISV = 0, ISS = 0x00000005
[ 102.228887] CM = 0, WnR = 0
[ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
[ 102.238572] [0000000000000006] pgd=0000000000000000, pud=0000000000000000
[ 102.245448] Internal error: Oops: 96000005 [#1] SMP
[ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
[ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
[ 102.280409] pc : page_mapping+0x24/0x144
[ 102.280415] lr : __dump_page+0x34/0x3dc
[ 102.292923] sp : ffff00003a5cfd10
[ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
[ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
[ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
[ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
[ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
[ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
[ 102.328049] x17: 0000000000000000 x16: 0000000000000000
[ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
[ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
[ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
[ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
[ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
[ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
[ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
[ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
[ 102.375782] Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____))
[ 102.382648] Call trace:
[ 102.385091] page_mapping+0x24/0x144
[ 102.388659] __dump_page+0x34/0x3dc
[ 102.392140] dump_page+0x28/0x4c
[ 102.395363] kmemleak_scan+0x4ac/0x680
[ 102.399106] kmemleak_scan_thread+0xb4/0xdc
[ 102.403285] kthread+0x12c/0x13c
[ 102.406509] ret_from_fork+0x10/0x18
[ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
[ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
[ 102.420966] Kernel panic - not syncing: Fatal exception
[ 102.426293] SMP: stopping secondary CPUs
[ 102.431830] Kernel Offset: disabled
[ 102.435311] CPU features: 0x002,20000c38
[ 102.439223] Memory Limit: none
[ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to
have holes")
Signed-off-by: Qian Cai <cai@lca.pw>
---
include/linux/memory_hotplug.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 07da5c6c5ba0..b8b36e6ac43b 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -26,7 +26,7 @@ struct vmem_altmap;
struct page *___page = NULL; \
unsigned long ___nr = pfn_to_section_nr(pfn); \
\
- if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\
+ if (online_section_nr(___nr) && pfn_valid(pfn)) \
___page = pfn_to_page(pfn); \
___page; \
})
--
2.17.2 (Apple Git-113)
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-18 2:16 ` [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page() Qian Cai
@ 2019-01-21 9:53 ` Michal Hocko
2019-01-21 16:38 ` Qian Cai
0 siblings, 1 reply; 11+ messages in thread
From: Michal Hocko @ 2019-01-21 9:53 UTC (permalink / raw)
To: Qian Cai; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On Thu 17-01-19 21:16:50, Qian Cai wrote:
> On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
> with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
> not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is
> uninitialized.
>
> This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little
> optimization while scanning") starts to use pfn_to_online_page() instead
> of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case,
> pfn_to_online_page() does not call memblock_is_map_memory() while
> pfn_valid() does.
How come there is an online section which has an pfn_valid==F? We do
allocate the full section worth of struct pages so there is a valid
struct page. Is there any hole inside this section?
Isn't this a problem that the particular struct page hasn't been
intialized properly?
> [1]
> [ 102.195320] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006
> [ 102.204113] Mem abort info:
> [ 102.206921] ESR = 0x96000005
> [ 102.209997] Exception class = DABT (current EL), IL = 32 bits
> [ 102.215926] SET = 0, FnV = 0
> [ 102.218993] EA = 0, S1PTW = 0
> [ 102.222150] Data abort info:
> [ 102.225047] ISV = 0, ISS = 0x00000005
> [ 102.228887] CM = 0, WnR = 0
> [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
> [ 102.238572] [0000000000000006] pgd=0000000000000000, pud=0000000000000000
> [ 102.245448] Internal error: Oops: 96000005 [#1] SMP
> [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
> [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
> [ 102.280409] pc : page_mapping+0x24/0x144
> [ 102.280415] lr : __dump_page+0x34/0x3dc
> [ 102.292923] sp : ffff00003a5cfd10
> [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
> [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
> [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
> [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
> [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
> [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
> [ 102.328049] x17: 0000000000000000 x16: 0000000000000000
> [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
> [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
> [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
> [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
> [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
> [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
> [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
> [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
> [ 102.375782] Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____))
> [ 102.382648] Call trace:
> [ 102.385091] page_mapping+0x24/0x144
> [ 102.388659] __dump_page+0x34/0x3dc
> [ 102.392140] dump_page+0x28/0x4c
> [ 102.395363] kmemleak_scan+0x4ac/0x680
> [ 102.399106] kmemleak_scan_thread+0xb4/0xdc
> [ 102.403285] kthread+0x12c/0x13c
> [ 102.406509] ret_from_fork+0x10/0x18
> [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
> [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
> [ 102.420966] Kernel panic - not syncing: Fatal exception
> [ 102.426293] SMP: stopping secondary CPUs
> [ 102.431830] Kernel Offset: disabled
> [ 102.435311] CPU features: 0x002,20000c38
> [ 102.439223] Memory Limit: none
> [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
>
> Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to
> have holes")
Did you mean
Fixes: 9f1eb38e0e11 ("mm, kmemleak: little optimization while scanning")
> Signed-off-by: Qian Cai <cai@lca.pw>
> ---
> include/linux/memory_hotplug.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 07da5c6c5ba0..b8b36e6ac43b 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -26,7 +26,7 @@ struct vmem_altmap;
> struct page *___page = NULL; \
> unsigned long ___nr = pfn_to_section_nr(pfn); \
> \
> - if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\
> + if (online_section_nr(___nr) && pfn_valid(pfn)) \
> ___page = pfn_to_page(pfn); \
Why have you removed the bound check? Is this safe?
Regarding the fix, I am not really sure TBH. If the secion is online
then we assume all struct pages to be initialized. If anything this
should be limited to werid arches which might have holes so
pfn_valid_within().
> ___page; \
> })
> --
> 2.17.2 (Apple Git-113)
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-21 9:53 ` Michal Hocko
@ 2019-01-21 16:38 ` Qian Cai
2019-01-21 17:58 ` Qian Cai
2019-01-21 18:19 ` Michal Hocko
0 siblings, 2 replies; 11+ messages in thread
From: Qian Cai @ 2019-01-21 16:38 UTC (permalink / raw)
To: Michal Hocko; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On 1/21/19 4:53 AM, Michal Hocko wrote:
> On Thu 17-01-19 21:16:50, Qian Cai wrote:
>> On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
>> with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
>> not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is
>> uninitialized.
>>
>> This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little
>> optimization while scanning") starts to use pfn_to_online_page() instead
>> of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case,
>> pfn_to_online_page() does not call memblock_is_map_memory() while
>> pfn_valid() does.
>
> How come there is an online section which has an pfn_valid==F? We do
> allocate the full section worth of struct pages so there is a valid
> struct page. Is there any hole inside this section?
It has CONFIG_HOLES_IN_ZONE=y.
>
> Isn't this a problem that the particular struct page hasn't been
> intialized properly?
>
>> [1]
>> [ 102.195320] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000006
>> [ 102.204113] Mem abort info:
>> [ 102.206921] ESR = 0x96000005
>> [ 102.209997] Exception class = DABT (current EL), IL = 32 bits
>> [ 102.215926] SET = 0, FnV = 0
>> [ 102.218993] EA = 0, S1PTW = 0
>> [ 102.222150] Data abort info:
>> [ 102.225047] ISV = 0, ISS = 0x00000005
>> [ 102.228887] CM = 0, WnR = 0
>> [ 102.231866] user pgtable: 64k pages, 48-bit VAs, pgdp = (____ptrval____)
>> [ 102.238572] [0000000000000006] pgd=0000000000000000, pud=0000000000000000
>> [ 102.245448] Internal error: Oops: 96000005 [#1] SMP
>> [ 102.264062] CPU: 60 PID: 1408 Comm: kmemleak Not tainted 5.0.0-rc2+ #8
>> [ 102.280403] pstate: 60400009 (nZCv daif +PAN -UAO)
>> [ 102.280409] pc : page_mapping+0x24/0x144
>> [ 102.280415] lr : __dump_page+0x34/0x3dc
>> [ 102.292923] sp : ffff00003a5cfd10
>> [ 102.296229] x29: ffff00003a5cfd10 x28: 000000000000802f
>> [ 102.301533] x27: 0000000000000000 x26: 0000000000277d00
>> [ 102.306835] x25: ffff000010791f56 x24: ffff7fe000000000
>> [ 102.312138] x23: ffff000010772f8b x22: ffff00001125f670
>> [ 102.317442] x21: ffff000011311000 x20: ffff000010772f8b
>> [ 102.322747] x19: fffffffffffffffe x18: 0000000000000000
>> [ 102.328049] x17: 0000000000000000 x16: 0000000000000000
>> [ 102.333352] x15: 0000000000000000 x14: ffff802698b19600
>> [ 102.338654] x13: ffff802698b1a200 x12: ffff802698b16f00
>> [ 102.343956] x11: ffff802698b1a400 x10: 0000000000001400
>> [ 102.349260] x9 : 0000000000000001 x8 : ffff00001121a000
>> [ 102.354563] x7 : 0000000000000000 x6 : ffff0000102c53b8
>> [ 102.359868] x5 : 0000000000000000 x4 : 0000000000000003
>> [ 102.365173] x3 : 0000000000000100 x2 : 0000000000000000
>> [ 102.370476] x1 : ffff000010772f8b x0 : ffffffffffffffff
>> [ 102.375782] Process kmemleak (pid: 1408, stack limit = 0x(____ptrval____))
>> [ 102.382648] Call trace:
>> [ 102.385091] page_mapping+0x24/0x144
>> [ 102.388659] __dump_page+0x34/0x3dc
>> [ 102.392140] dump_page+0x28/0x4c
>> [ 102.395363] kmemleak_scan+0x4ac/0x680
>> [ 102.399106] kmemleak_scan_thread+0xb4/0xdc
>> [ 102.403285] kthread+0x12c/0x13c
>> [ 102.406509] ret_from_fork+0x10/0x18
>> [ 102.410080] Code: d503201f f9400660 36000040 d1000413 (f9400661)
>> [ 102.416357] ---[ end trace 4d4bd7f573490c8e ]---
>> [ 102.420966] Kernel panic - not syncing: Fatal exception
>> [ 102.426293] SMP: stopping secondary CPUs
>> [ 102.431830] Kernel Offset: disabled
>> [ 102.435311] CPU features: 0x002,20000c38
>> [ 102.439223] Memory Limit: none
>> [ 102.442384] ---[ end Kernel panic - not syncing: Fatal exception ]---
>>
>> Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to
>> have holes")
>
> Did you mean
> Fixes: 9f1eb38e0e11 ("mm, kmemleak: little optimization while scanning")
No, pfn_to_online_page() missed a few checks compared to pfn_valid() at least on
arm64 where the returned pfn is no longer valid (where pfn_valid() will skip those).
2d070eab2e82 introduced pfn_to_online_page(), so it was targeted to fix it.
>
>> Signed-off-by: Qian Cai <cai@lca.pw>
>> ---
>> include/linux/memory_hotplug.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
>> index 07da5c6c5ba0..b8b36e6ac43b 100644
>> --- a/include/linux/memory_hotplug.h
>> +++ b/include/linux/memory_hotplug.h
>> @@ -26,7 +26,7 @@ struct vmem_altmap;
>> struct page *___page = NULL; \
>> unsigned long ___nr = pfn_to_section_nr(pfn); \
>> \
>> - if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\
>> + if (online_section_nr(___nr) && pfn_valid(pfn)) \
>> ___page = pfn_to_page(pfn); \
>
> Why have you removed the bound check? Is this safe?
> Regarding the fix, I am not really sure TBH. If the secion is online
> then we assume all struct pages to be initialized. If anything this
> should be limited to werid arches which might have holes so
> pfn_valid_within().
It looks to me at least on arm64 and x86_64, it has done this check in
pfn_valid() already.
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-21 16:38 ` Qian Cai
@ 2019-01-21 17:58 ` Qian Cai
2019-01-21 18:36 ` Michal Hocko
2019-01-21 18:19 ` Michal Hocko
1 sibling, 1 reply; 11+ messages in thread
From: Qian Cai @ 2019-01-21 17:58 UTC (permalink / raw)
To: Michal Hocko; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On 1/21/19 11:38 AM, Qian Cai wrote:
>
>
> On 1/21/19 4:53 AM, Michal Hocko wrote:
>> On Thu 17-01-19 21:16:50, Qian Cai wrote:
>>> On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
>>> with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
>>> not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is
>>> uninitialized.
>>>
>>> This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little
>>> optimization while scanning") starts to use pfn_to_online_page() instead
>>> of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case,
>>> pfn_to_online_page() does not call memblock_is_map_memory() while
>>> pfn_valid() does.
>>
>> How come there is an online section which has an pfn_valid==F? We do
>> allocate the full section worth of struct pages so there is a valid
>> struct page. Is there any hole inside this section?
>
> It has CONFIG_HOLES_IN_ZONE=y.
Actually, this does not seem have anything to do with holes.
68709f45385a arm64: only consider memblocks with NOMAP cleared for linear mapping
This causes pages marked as nomap being no long reassigned to the new zone in
memmap_init_zone() by calling __init_single_page().
There is an old discussion for this topic.
https://lkml.org/lkml/2016/11/30/566
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-21 16:38 ` Qian Cai
2019-01-21 17:58 ` Qian Cai
@ 2019-01-21 18:19 ` Michal Hocko
2019-01-21 18:37 ` Qian Cai
1 sibling, 1 reply; 11+ messages in thread
From: Michal Hocko @ 2019-01-21 18:19 UTC (permalink / raw)
To: Qian Cai; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On Mon 21-01-19 11:38:49, Qian Cai wrote:
>
>
> On 1/21/19 4:53 AM, Michal Hocko wrote:
> > On Thu 17-01-19 21:16:50, Qian Cai wrote:
[...]
> >> Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to
> >> have holes")
> >
> > Did you mean
> > Fixes: 9f1eb38e0e11 ("mm, kmemleak: little optimization while scanning")
>
> No, pfn_to_online_page() missed a few checks compared to pfn_valid() at least on
> arm64 where the returned pfn is no longer valid (where pfn_valid() will skip those).
>
> 2d070eab2e82 introduced pfn_to_online_page(), so it was targeted to fix it.
But it is 9f1eb38e0e11 which has replaced pfn_valid by
pfn_to_online_page.
>
> >
> >> Signed-off-by: Qian Cai <cai@lca.pw>
> >> ---
> >> include/linux/memory_hotplug.h | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> >> index 07da5c6c5ba0..b8b36e6ac43b 100644
> >> --- a/include/linux/memory_hotplug.h
> >> +++ b/include/linux/memory_hotplug.h
> >> @@ -26,7 +26,7 @@ struct vmem_altmap;
> >> struct page *___page = NULL; \
> >> unsigned long ___nr = pfn_to_section_nr(pfn); \
> >> \
> >> - if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\
> >> + if (online_section_nr(___nr) && pfn_valid(pfn)) \
> >> ___page = pfn_to_page(pfn); \
> >
> > Why have you removed the bound check? Is this safe?
> > Regarding the fix, I am not really sure TBH. If the secion is online
> > then we assume all struct pages to be initialized. If anything this
> > should be limited to werid arches which might have holes so
> > pfn_valid_within().
>
> It looks to me at least on arm64 and x86_64, it has done this check in
> pfn_valid() already.
>
> if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> return 0
But an everflow could happen before pfn_valid is evaluated, no?
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-21 17:58 ` Qian Cai
@ 2019-01-21 18:36 ` Michal Hocko
0 siblings, 0 replies; 11+ messages in thread
From: Michal Hocko @ 2019-01-21 18:36 UTC (permalink / raw)
To: Qian Cai; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On Mon 21-01-19 12:58:46, Qian Cai wrote:
>
>
> On 1/21/19 11:38 AM, Qian Cai wrote:
> >
> >
> > On 1/21/19 4:53 AM, Michal Hocko wrote:
> >> On Thu 17-01-19 21:16:50, Qian Cai wrote:
> >>> On an arm64 ThunderX2 server, the first kmemleak scan would crash [1]
> >>> with CONFIG_DEBUG_VM_PGFLAGS=y due to page_to_nid() found a pfn that is
> >>> not directly mapped (MEMBLOCK_NOMAP). Hence, the page->flags is
> >>> uninitialized.
> >>>
> >>> This is due to the commit 9f1eb38e0e11 ("mm, kmemleak: little
> >>> optimization while scanning") starts to use pfn_to_online_page() instead
> >>> of pfn_valid(). However, in the CONFIG_MEMORY_HOTPLUG=y case,
> >>> pfn_to_online_page() does not call memblock_is_map_memory() while
> >>> pfn_valid() does.
> >>
> >> How come there is an online section which has an pfn_valid==F? We do
> >> allocate the full section worth of struct pages so there is a valid
> >> struct page. Is there any hole inside this section?
> >
> > It has CONFIG_HOLES_IN_ZONE=y.
>
> Actually, this does not seem have anything to do with holes.
>
> 68709f45385a arm64: only consider memblocks with NOMAP cleared for linear mapping
>
> This causes pages marked as nomap being no long reassigned to the new zone in
> memmap_init_zone() by calling __init_single_page().
Thanks for the pointer. This sched some light but I cannot say I would
understand all the details.
> There is an old discussion for this topic.
> https://lkml.org/lkml/2016/11/30/566
Hmm, I see. The documentation is not the best (mea culpa)
* Return page for the valid pfn only if the page is online. All pfn
* walkers which rely on the fully initialized page->flags and others
* should use this rather than pfn_valid && pfn_to_page
This suggests that the pfn is _valid_ when using pfn_to_online_page and
some callers indeed do so. Some of them don't though which is probably
because the later part of the documentation suggests that it should
replace pfn_valid & pfn_to_page. Thinking about this more, I guess we do
not want to put an additional burden on callers and require pfn_valid to
be called as well. This is just error prone and can lead to problems
like this one.
So I agree with your change (modulo the range check) but please make
sure to make all this information to the changelog.
Thanks!
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page()
2019-01-21 18:19 ` Michal Hocko
@ 2019-01-21 18:37 ` Qian Cai
0 siblings, 0 replies; 11+ messages in thread
From: Qian Cai @ 2019-01-21 18:37 UTC (permalink / raw)
To: Michal Hocko; +Cc: akpm, osalvador, catalin.marinas, vbabka, linux-mm
On 1/21/19 1:19 PM, Michal Hocko wrote:
> On Mon 21-01-19 11:38:49, Qian Cai wrote:
>>
>>
>> On 1/21/19 4:53 AM, Michal Hocko wrote:
>>> On Thu 17-01-19 21:16:50, Qian Cai wrote:
> [...]
>>>> Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to
>>>> have holes")
>>>
>>> Did you mean
>>> Fixes: 9f1eb38e0e11 ("mm, kmemleak: little optimization while scanning")
>>
>> No, pfn_to_online_page() missed a few checks compared to pfn_valid() at least on
>> arm64 where the returned pfn is no longer valid (where pfn_valid() will skip those).
>>
>> 2d070eab2e82 introduced pfn_to_online_page(), so it was targeted to fix it.
>
> But it is 9f1eb38e0e11 which has replaced pfn_valid by
> pfn_to_online_page.
Well, the comment of pfn_to_online_page() said,
/*
* Return page for the valid pfn only if the page is online.
* All pfn walkers which rely on the fully initialized
* page->flags and others should use this rather than
* pfn_valid && pfn_to_page
*/
That seems incorrect to me in the first place, as it currently not return "fully
initialized page->flags" pages in arm64.
Once this fixed, there is no problem with 9f1eb38e0e11. It seems to me
9f1eb38e0e11 just depends on a broken interface, so it is better to fix the
broken interface.
>
>>
>>>
>>>> Signed-off-by: Qian Cai <cai@lca.pw>
>>>> ---
>>>> include/linux/memory_hotplug.h | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
>>>> index 07da5c6c5ba0..b8b36e6ac43b 100644
>>>> --- a/include/linux/memory_hotplug.h
>>>> +++ b/include/linux/memory_hotplug.h
>>>> @@ -26,7 +26,7 @@ struct vmem_altmap;
>>>> struct page *___page = NULL; \
>>>> unsigned long ___nr = pfn_to_section_nr(pfn); \
>>>> \
>>>> - if (___nr < NR_MEM_SECTIONS && online_section_nr(___nr))\
>>>> + if (online_section_nr(___nr) && pfn_valid(pfn)) \
>>>> ___page = pfn_to_page(pfn); \
>>>
>>> Why have you removed the bound check? Is this safe?
>>> Regarding the fix, I am not really sure TBH. If the secion is online
>>> then we assume all struct pages to be initialized. If anything this
>>> should be limited to werid arches which might have holes so
>>> pfn_valid_within().
>>
>> It looks to me at least on arm64 and x86_64, it has done this check in
>> pfn_valid() already.
>>
>> if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
>> return 0
>
> But an everflow could happen before pfn_valid is evaluated, no?
>
I guess you mean "overflow". I'll probably keep that check and use
pfn_valid_within() anyway, so I could optimize the checking if
CONFIG_HOLES_IN_ZONE=n.
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2019-01-21 18:37 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-01-17 17:36 kmemleak scan crash due to invalid PFNs Qian Cai
2019-01-17 18:50 ` Oscar Salvador
2019-01-17 18:50 ` Oscar Salvador
2019-01-17 18:58 ` Oscar Salvador
2019-01-18 2:16 ` [PATCH] mm/hotplug: invalid PFNs from pfn_to_online_page() Qian Cai
2019-01-21 9:53 ` Michal Hocko
2019-01-21 16:38 ` Qian Cai
2019-01-21 17:58 ` Qian Cai
2019-01-21 18:36 ` Michal Hocko
2019-01-21 18:19 ` Michal Hocko
2019-01-21 18:37 ` Qian Cai
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