* [PATCH] mm: do not try to migrate lru_gen if it's not associated with a memcg
@ 2023-01-15 13:33 msizanoen1
2023-01-15 13:46 ` [PATCH v2] " msizanoen1
0 siblings, 1 reply; 5+ messages in thread
From: msizanoen1 @ 2023-01-15 13:33 UTC (permalink / raw)
To: Andrew Morton; +Cc: Yu Zhao, msizanoen, linux-mm, linux-kernel
From: msizanoen <msizanoen@qtmlabs.xyz>
In some cases, memory cgroup migration can be initiated by userspace
right after a process was created and right before `lru_gen_add_mm()` is
called (e.g. by some program watching a cgroup and moving away any
processes it detects[1]), which results in the following sequence of
WARNs followed by an Oops as the kernel attempts to perform a
`lru_gen_add_mm()` twice on the same `mm`:
[26181.135304] ------------[ cut here ]------------
[26181.135309] WARNING: CPU: 0 PID: 57083 at mm/vmscan.c:3299 lru_gen_migrate_mm+0x76/0x80
[26181.135484] CPU: 0 PID: 57083 Comm: cgroupify Kdump: loaded Tainted: P OE 6.1.5-200.fc37.x86_64 #1
[26181.135489] RIP: 0010:lru_gen_migrate_mm+0x76/0x80
[26181.135518] Call Trace:
[26181.135521] <TASK>
[26181.135525] mem_cgroup_attach+0x88/0x90
[26181.135531] cgroup_migrate_execute+0x213/0x470
[26181.135536] cgroup_attach_task+0x11c/0x1c0
[26181.135540] ? cgroup_attach_permissions+0x159/0x1c0
[26181.135545] __cgroup_procs_write+0x10e/0x140
[26181.135550] cgroup_procs_write+0x13/0x20
[26181.135553] kernfs_fop_write_iter+0x11e/0x1f0
[26181.135559] vfs_write+0x222/0x3e0
[26181.135565] ksys_write+0x5b/0xd0
[26181.135569] do_syscall_64+0x5b/0x80
[26181.135573] ? syscall_exit_to_user_mode+0x17/0x40
[26181.135578] ? do_syscall_64+0x67/0x80
[26181.135581] ? do_syscall_64+0x67/0x80
[26181.135584] ? exc_page_fault+0x70/0x170
[26181.135588] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.135592] RIP: 0033:0x7fd18996a0c4
[26181.135633] </TASK>
[26181.135635] ---[ end trace 0000000000000000 ]---
[26181.135643] ------------[ cut here ]------------
[26181.135644] WARNING: CPU: 0 PID: 57083 at mm/vmscan.c:3300 lru_gen_migrate_mm+0x72/0x80
[26181.135804] CPU: 0 PID: 57083 Comm: cgroupify Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.135808] RIP: 0010:lru_gen_migrate_mm+0x72/0x80
[26181.135835] Call Trace:
[26181.135837] <TASK>
[26181.135838] mem_cgroup_attach+0x88/0x90
[26181.135844] cgroup_migrate_execute+0x213/0x470
[26181.135848] cgroup_attach_task+0x11c/0x1c0
[26181.135852] ? cgroup_attach_permissions+0x159/0x1c0
[26181.135857] __cgroup_procs_write+0x10e/0x140
[26181.135861] cgroup_procs_write+0x13/0x20
[26181.135864] kernfs_fop_write_iter+0x11e/0x1f0
[26181.135870] vfs_write+0x222/0x3e0
[26181.135876] ksys_write+0x5b/0xd0
[26181.135880] do_syscall_64+0x5b/0x80
[26181.135884] ? syscall_exit_to_user_mode+0x17/0x40
[26181.135889] ? do_syscall_64+0x67/0x80
[26181.135892] ? do_syscall_64+0x67/0x80
[26181.135895] ? exc_page_fault+0x70/0x170
[26181.135900] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.135903] RIP: 0033:0x7fd18996a0c4
[26181.135985] </TASK>
[26181.135986] ---[ end trace 0000000000000000 ]---
[26181.143062] ------------[ cut here ]------------
[26181.143066] WARNING: CPU: 0 PID: 57554 at mm/vmscan.c:3211 lru_gen_add_mm+0x159/0x180
[26181.143240] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143246] RIP: 0010:lru_gen_add_mm+0x159/0x180
[26181.143274] Call Trace:
[26181.143277] <TASK>
[26181.143281] kernel_clone+0x20c/0x400
[26181.143285] ? wp_page_copy+0x36f/0x6f0
[26181.143290] __do_sys_clone+0x64/0x70
[26181.143295] do_syscall_64+0x5b/0x80
[26181.143299] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143303] ? do_syscall_64+0x67/0x80
[26181.143307] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143310] ? do_syscall_64+0x67/0x80
[26181.143314] ? handle_mm_fault+0xdb/0x2d0
[26181.143317] ? do_user_addr_fault+0x1ef/0x690
[26181.143322] ? _raw_spin_lock+0x13/0x40
[26181.143326] ? exc_page_fault+0x70/0x170
[26181.143330] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143333] RIP: 0033:0x7fa3b7131d47
[26181.143379] </TASK>
[26181.143380] ---[ end trace 0000000000000000 ]---
[26181.143387] ------------[ cut here ]------------
[26181.143388] WARNING: CPU: 0 PID: 57554 at mm/vmscan.c:3213 lru_gen_add_mm+0x16a/0x180
[26181.143535] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143539] RIP: 0010:lru_gen_add_mm+0x16a/0x180
[26181.143564] Call Trace:
[26181.143565] <TASK>
[26181.143567] kernel_clone+0x20c/0x400
[26181.143570] ? wp_page_copy+0x36f/0x6f0
[26181.143574] __do_sys_clone+0x64/0x70
[26181.143578] do_syscall_64+0x5b/0x80
[26181.143581] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143585] ? do_syscall_64+0x67/0x80
[26181.143588] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143592] ? do_syscall_64+0x67/0x80
[26181.143595] ? handle_mm_fault+0xdb/0x2d0
[26181.143599] ? do_user_addr_fault+0x1ef/0x690
[26181.143603] ? _raw_spin_lock+0x13/0x40
[26181.143606] ? exc_page_fault+0x70/0x170
[26181.143610] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143614] RIP: 0033:0x7fa3b7131d47
[26181.143638] </TASK>
[26181.143639] ---[ end trace 0000000000000000 ]---
[26181.143641] list_add double add: new=ffff91c15edec3d8, prev=ffff91c15edec3d8, next=ffff91c1e3f48878.
[26181.143658] ------------[ cut here ]------------
[26181.143659] kernel BUG at lib/list_debug.c:33!
[26181.143667] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[26181.143670] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143675] RIP: 0010:__list_add_valid.cold+0x23/0x5b
[26181.143707] Call Trace:
[26181.143708] <TASK>
[26181.143710] lru_gen_add_mm+0x10a/0x180
[26181.143716] kernel_clone+0x20c/0x400
[26181.143719] ? wp_page_copy+0x36f/0x6f0
[26181.143723] __do_sys_clone+0x64/0x70
[26181.143728] do_syscall_64+0x5b/0x80
[26181.143732] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143736] ? do_syscall_64+0x67/0x80
[26181.143740] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143744] ? do_syscall_64+0x67/0x80
[26181.143748] ? handle_mm_fault+0xdb/0x2d0
[26181.143753] ? do_user_addr_fault+0x1ef/0x690
[26181.143757] ? _raw_spin_lock+0x13/0x40
[26181.143761] ? exc_page_fault+0x70/0x170
[26181.143765] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143769] RIP: 0033:0x7fa3b7131d47
[26181.143796] </TASK>
Fix this by simply leaving the lru_gen alone if it has not been
associated with a memcg yet, as it should eventually be assigned to the
right cgroup anyway.
[1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
Signed-off-by: N/A (patch should not be copyrightable)
---
mm/vmscan.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd6637fcd8f9..0cac40e7484c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3323,13 +3323,19 @@ void lru_gen_migrate_mm(struct mm_struct *mm)
if (mem_cgroup_disabled())
return;
+ /* This could happen if cgroup migration is invoked before the process
+ * lru_gen is associated with a memcg (e.g. during process creation).
+ * Simply ignore it in this case as the lru_gen will get assigned the
+ * right cgroup later. */
+ if (!mm->lru_gen.memcg)
+ return;
+
rcu_read_lock();
memcg = mem_cgroup_from_task(task);
rcu_read_unlock();
if (memcg == mm->lru_gen.memcg)
return;
- VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
lru_gen_del_mm(mm);
--
2.39.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v2] mm: do not try to migrate lru_gen if it's not associated with a memcg
2023-01-15 13:33 [PATCH] mm: do not try to migrate lru_gen if it's not associated with a memcg msizanoen1
@ 2023-01-15 13:46 ` msizanoen1
2023-01-15 23:13 ` Yu Zhao
0 siblings, 1 reply; 5+ messages in thread
From: msizanoen1 @ 2023-01-15 13:46 UTC (permalink / raw)
To: Andrew Morton; +Cc: Yu Zhao, msizanoen1, stable, linux-mm, linux-kernel
In some cases, memory cgroup migration can be initiated by userspace
right after a process was created and right before `lru_gen_add_mm()` is
called (e.g. by some program watching a cgroup and moving away any
processes it detects[1]), which results in the following sequence of
WARNs followed by an Oops as the kernel attempts to perform a
`lru_gen_add_mm()` twice on the same `mm`:
[26181.135304] ------------[ cut here ]------------
[26181.135309] WARNING: CPU: 0 PID: 57083 at mm/vmscan.c:3299 lru_gen_migrate_mm+0x76/0x80
[26181.135484] CPU: 0 PID: 57083 Comm: cgroupify Kdump: loaded Tainted: P OE 6.1.5-200.fc37.x86_64 #1
[26181.135489] RIP: 0010:lru_gen_migrate_mm+0x76/0x80
[26181.135518] Call Trace:
[26181.135521] <TASK>
[26181.135525] mem_cgroup_attach+0x88/0x90
[26181.135531] cgroup_migrate_execute+0x213/0x470
[26181.135536] cgroup_attach_task+0x11c/0x1c0
[26181.135540] ? cgroup_attach_permissions+0x159/0x1c0
[26181.135545] __cgroup_procs_write+0x10e/0x140
[26181.135550] cgroup_procs_write+0x13/0x20
[26181.135553] kernfs_fop_write_iter+0x11e/0x1f0
[26181.135559] vfs_write+0x222/0x3e0
[26181.135565] ksys_write+0x5b/0xd0
[26181.135569] do_syscall_64+0x5b/0x80
[26181.135573] ? syscall_exit_to_user_mode+0x17/0x40
[26181.135578] ? do_syscall_64+0x67/0x80
[26181.135581] ? do_syscall_64+0x67/0x80
[26181.135584] ? exc_page_fault+0x70/0x170
[26181.135588] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.135592] RIP: 0033:0x7fd18996a0c4
[26181.135633] </TASK>
[26181.135635] ---[ end trace 0000000000000000 ]---
[26181.135643] ------------[ cut here ]------------
[26181.135644] WARNING: CPU: 0 PID: 57083 at mm/vmscan.c:3300 lru_gen_migrate_mm+0x72/0x80
[26181.135804] CPU: 0 PID: 57083 Comm: cgroupify Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.135808] RIP: 0010:lru_gen_migrate_mm+0x72/0x80
[26181.135835] Call Trace:
[26181.135837] <TASK>
[26181.135838] mem_cgroup_attach+0x88/0x90
[26181.135844] cgroup_migrate_execute+0x213/0x470
[26181.135848] cgroup_attach_task+0x11c/0x1c0
[26181.135852] ? cgroup_attach_permissions+0x159/0x1c0
[26181.135857] __cgroup_procs_write+0x10e/0x140
[26181.135861] cgroup_procs_write+0x13/0x20
[26181.135864] kernfs_fop_write_iter+0x11e/0x1f0
[26181.135870] vfs_write+0x222/0x3e0
[26181.135876] ksys_write+0x5b/0xd0
[26181.135880] do_syscall_64+0x5b/0x80
[26181.135884] ? syscall_exit_to_user_mode+0x17/0x40
[26181.135889] ? do_syscall_64+0x67/0x80
[26181.135892] ? do_syscall_64+0x67/0x80
[26181.135895] ? exc_page_fault+0x70/0x170
[26181.135900] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.135903] RIP: 0033:0x7fd18996a0c4
[26181.135985] </TASK>
[26181.135986] ---[ end trace 0000000000000000 ]---
[26181.143062] ------------[ cut here ]------------
[26181.143066] WARNING: CPU: 0 PID: 57554 at mm/vmscan.c:3211 lru_gen_add_mm+0x159/0x180
[26181.143240] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143246] RIP: 0010:lru_gen_add_mm+0x159/0x180
[26181.143274] Call Trace:
[26181.143277] <TASK>
[26181.143281] kernel_clone+0x20c/0x400
[26181.143285] ? wp_page_copy+0x36f/0x6f0
[26181.143290] __do_sys_clone+0x64/0x70
[26181.143295] do_syscall_64+0x5b/0x80
[26181.143299] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143303] ? do_syscall_64+0x67/0x80
[26181.143307] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143310] ? do_syscall_64+0x67/0x80
[26181.143314] ? handle_mm_fault+0xdb/0x2d0
[26181.143317] ? do_user_addr_fault+0x1ef/0x690
[26181.143322] ? _raw_spin_lock+0x13/0x40
[26181.143326] ? exc_page_fault+0x70/0x170
[26181.143330] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143333] RIP: 0033:0x7fa3b7131d47
[26181.143379] </TASK>
[26181.143380] ---[ end trace 0000000000000000 ]---
[26181.143387] ------------[ cut here ]------------
[26181.143388] WARNING: CPU: 0 PID: 57554 at mm/vmscan.c:3213 lru_gen_add_mm+0x16a/0x180
[26181.143535] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143539] RIP: 0010:lru_gen_add_mm+0x16a/0x180
[26181.143564] Call Trace:
[26181.143565] <TASK>
[26181.143567] kernel_clone+0x20c/0x400
[26181.143570] ? wp_page_copy+0x36f/0x6f0
[26181.143574] __do_sys_clone+0x64/0x70
[26181.143578] do_syscall_64+0x5b/0x80
[26181.143581] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143585] ? do_syscall_64+0x67/0x80
[26181.143588] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143592] ? do_syscall_64+0x67/0x80
[26181.143595] ? handle_mm_fault+0xdb/0x2d0
[26181.143599] ? do_user_addr_fault+0x1ef/0x690
[26181.143603] ? _raw_spin_lock+0x13/0x40
[26181.143606] ? exc_page_fault+0x70/0x170
[26181.143610] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143614] RIP: 0033:0x7fa3b7131d47
[26181.143638] </TASK>
[26181.143639] ---[ end trace 0000000000000000 ]---
[26181.143641] list_add double add: new=ffff91c15edec3d8, prev=ffff91c15edec3d8, next=ffff91c1e3f48878.
[26181.143658] ------------[ cut here ]------------
[26181.143659] kernel BUG at lib/list_debug.c:33!
[26181.143667] invalid opcode: 0000 [#1] PREEMPT SMP PTI
[26181.143670] CPU: 0 PID: 57554 Comm: xdg-mime Kdump: loaded Tainted: P W OE 6.1.5-200.fc37.x86_64 #1
[26181.143675] RIP: 0010:__list_add_valid.cold+0x23/0x5b
[26181.143707] Call Trace:
[26181.143708] <TASK>
[26181.143710] lru_gen_add_mm+0x10a/0x180
[26181.143716] kernel_clone+0x20c/0x400
[26181.143719] ? wp_page_copy+0x36f/0x6f0
[26181.143723] __do_sys_clone+0x64/0x70
[26181.143728] do_syscall_64+0x5b/0x80
[26181.143732] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143736] ? do_syscall_64+0x67/0x80
[26181.143740] ? syscall_exit_to_user_mode+0x17/0x40
[26181.143744] ? do_syscall_64+0x67/0x80
[26181.143748] ? handle_mm_fault+0xdb/0x2d0
[26181.143753] ? do_user_addr_fault+0x1ef/0x690
[26181.143757] ? _raw_spin_lock+0x13/0x40
[26181.143761] ? exc_page_fault+0x70/0x170
[26181.143765] entry_SYSCALL_64_after_hwframe+0x63/0xcd
[26181.143769] RIP: 0033:0x7fa3b7131d47
[26181.143796] </TASK>
Fix this by simply leaving the lru_gen alone if it has not been
associated with a memcg yet, as it should eventually be assigned to the
right cgroup anyway.
[1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
v2:
Added stable cc tags
Signed-off-by: N/A (patch should not be copyrightable)
Cc: stable@vger.kernel.org
---
mm/vmscan.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd6637fcd8f9..0cac40e7484c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3323,13 +3323,19 @@ void lru_gen_migrate_mm(struct mm_struct *mm)
if (mem_cgroup_disabled())
return;
+ /* This could happen if cgroup migration is invoked before the process
+ * lru_gen is associated with a memcg (e.g. during process creation).
+ * Simply ignore it in this case as the lru_gen will get assigned the
+ * right cgroup later. */
+ if (!mm->lru_gen.memcg)
+ return;
+
rcu_read_lock();
memcg = mem_cgroup_from_task(task);
rcu_read_unlock();
if (memcg == mm->lru_gen.memcg)
return;
- VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
lru_gen_del_mm(mm);
--
2.39.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm: do not try to migrate lru_gen if it's not associated with a memcg
2023-01-15 13:46 ` [PATCH v2] " msizanoen1
@ 2023-01-15 23:13 ` Yu Zhao
2023-01-16 3:01 ` msizanoen
2023-01-16 17:09 ` David Hildenbrand
0 siblings, 2 replies; 5+ messages in thread
From: Yu Zhao @ 2023-01-15 23:13 UTC (permalink / raw)
To: msizanoen1; +Cc: Andrew Morton, stable, linux-mm, linux-kernel
On Sun, Jan 15, 2023 at 6:47 AM msizanoen1 <msizanoen@qtmlabs.xyz> wrote:
>
> In some cases, memory cgroup migration can be initiated by userspace
> right after a process was created and right before `lru_gen_add_mm()` is
> called (e.g. by some program watching a cgroup and moving away any
> processes it detects[1]), which results in the following sequence of
> WARNs followed by an Oops as the kernel attempts to perform a
> `lru_gen_add_mm()` twice on the same `mm`:
...
> Fix this by simply leaving the lru_gen alone if it has not been
> associated with a memcg yet, as it should eventually be assigned to the
> right cgroup anyway.
>
> [1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
>
> v2:
> Added stable cc tags
>
> Signed-off-by: N/A (patch should not be copyrightable)
> Cc: stable@vger.kernel.org
Thanks for the fix. Cc'ing stable is the right thing to do. The
commit message and the comment styles could be easily adjusted to
align with the guidelines.
I don't think the N/A is acceptible though. I fully respect it if you
wish to remain anonymous -- I can send a similar fix crediting you
as the "anonymous user <msizanoen@qtmlabs.xyz>" who reported this bug.
A bit of background on how I broke it: an old version I have on 4.15
calls lru_gen_add_mm() before cgroup_post_fork(), which excludes
cgroup migrations by cgroup_threadgroup_rwsem. When I rebased it, I
made lru_gen_add_mm() depend on task_lock for the synchronization with
cgroup migrations -- the decoupling seemed (still seems) to make it
less complicated -- but this is not safe unless we have the check below.
> ---
> mm/vmscan.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index bd6637fcd8f9..0cac40e7484c 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -3323,13 +3323,19 @@ void lru_gen_migrate_mm(struct mm_struct *mm)
> if (mem_cgroup_disabled())
> return;
>
> + /* This could happen if cgroup migration is invoked before the process
> + * lru_gen is associated with a memcg (e.g. during process creation).
> + * Simply ignore it in this case as the lru_gen will get assigned the
> + * right cgroup later. */
> + if (!mm->lru_gen.memcg)
> + return;
> +
> rcu_read_lock();
> memcg = mem_cgroup_from_task(task);
> rcu_read_unlock();
> if (memcg == mm->lru_gen.memcg)
> return;
>
> - VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
> VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
>
> lru_gen_del_mm(mm);
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm: do not try to migrate lru_gen if it's not associated with a memcg
2023-01-15 23:13 ` Yu Zhao
@ 2023-01-16 3:01 ` msizanoen
2023-01-16 17:09 ` David Hildenbrand
1 sibling, 0 replies; 5+ messages in thread
From: msizanoen @ 2023-01-16 3:01 UTC (permalink / raw)
To: Yu Zhao; +Cc: Andrew Morton, stable, linux-mm, linux-kernel
On 1/16/23 06:13, Yu Zhao wrote:
> On Sun, Jan 15, 2023 at 6:47 AM msizanoen1 <msizanoen@qtmlabs.xyz> wrote:
>> In some cases, memory cgroup migration can be initiated by userspace
>> right after a process was created and right before `lru_gen_add_mm()` is
>> called (e.g. by some program watching a cgroup and moving away any
>> processes it detects[1]), which results in the following sequence of
>> WARNs followed by an Oops as the kernel attempts to perform a
>> `lru_gen_add_mm()` twice on the same `mm`:
> ...
>
>> Fix this by simply leaving the lru_gen alone if it has not been
>> associated with a memcg yet, as it should eventually be assigned to the
>> right cgroup anyway.
>>
>> [1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
>>
>> v2:
>> Added stable cc tags
>>
>> Signed-off-by: N/A (patch should not be copyrightable)
>> Cc: stable@vger.kernel.org
> Thanks for the fix. Cc'ing stable is the right thing to do. The
> commit message and the comment styles could be easily adjusted to
> align with the guidelines.
>
> I don't think the N/A is acceptible though. I fully respect it if you
> wish to remain anonymous -- I can send a similar fix crediting you
> as the "anonymous user <msizanoen@qtmlabs.xyz>" who reported this bug.
Sure, just add my email in the `Reported-by: ` and `Tested-by: ` lines
and git-send-email should automatically add me to the Cc list.
>
> A bit of background on how I broke it: an old version I have on 4.15
> calls lru_gen_add_mm() before cgroup_post_fork(), which excludes
> cgroup migrations by cgroup_threadgroup_rwsem. When I rebased it, I
> made lru_gen_add_mm() depend on task_lock for the synchronization with
> cgroup migrations -- the decoupling seemed (still seems) to make it
> less complicated -- but this is not safe unless we have the check below.
>
>
>
>
>> ---
>> mm/vmscan.c | 8 +++++++-
>> 1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index bd6637fcd8f9..0cac40e7484c 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -3323,13 +3323,19 @@ void lru_gen_migrate_mm(struct mm_struct *mm)
>> if (mem_cgroup_disabled())
>> return;
>>
>> + /* This could happen if cgroup migration is invoked before the process
>> + * lru_gen is associated with a memcg (e.g. during process creation).
>> + * Simply ignore it in this case as the lru_gen will get assigned the
>> + * right cgroup later. */
>> + if (!mm->lru_gen.memcg)
>> + return;
>> +
>> rcu_read_lock();
>> memcg = mem_cgroup_from_task(task);
>> rcu_read_unlock();
>> if (memcg == mm->lru_gen.memcg)
>> return;
>>
>> - VM_WARN_ON_ONCE(!mm->lru_gen.memcg);
>> VM_WARN_ON_ONCE(list_empty(&mm->lru_gen.list));
>>
>> lru_gen_del_mm(mm);
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] mm: do not try to migrate lru_gen if it's not associated with a memcg
2023-01-15 23:13 ` Yu Zhao
2023-01-16 3:01 ` msizanoen
@ 2023-01-16 17:09 ` David Hildenbrand
1 sibling, 0 replies; 5+ messages in thread
From: David Hildenbrand @ 2023-01-16 17:09 UTC (permalink / raw)
To: Yu Zhao, msizanoen1; +Cc: Andrew Morton, stable, linux-mm, linux-kernel
On 16.01.23 00:13, Yu Zhao wrote:
> On Sun, Jan 15, 2023 at 6:47 AM msizanoen1 <msizanoen@qtmlabs.xyz> wrote:
>>
>> In some cases, memory cgroup migration can be initiated by userspace
>> right after a process was created and right before `lru_gen_add_mm()` is
>> called (e.g. by some program watching a cgroup and moving away any
>> processes it detects[1]), which results in the following sequence of
>> WARNs followed by an Oops as the kernel attempts to perform a
>> `lru_gen_add_mm()` twice on the same `mm`:
>
> ...
>
>> Fix this by simply leaving the lru_gen alone if it has not been
>> associated with a memcg yet, as it should eventually be assigned to the
>> right cgroup anyway.
>>
>> [1]: https://gitlab.freedesktop.org/benzea/uresourced/-/blob/master/cgroupify/cgroupify.c
>>
>> v2:
>> Added stable cc tags
>>
>> Signed-off-by: N/A (patch should not be copyrightable)
>> Cc: stable@vger.kernel.org
>
> Thanks for the fix. Cc'ing stable is the right thing to do. The
> commit message and the comment styles could be easily adjusted to
> align with the guidelines.
>
> I don't think the N/A is acceptible though. I fully respect it if you
> wish to remain anonymous -- I can send a similar fix crediting you
> as the "anonymous user <msizanoen@qtmlabs.xyz>" who reported this bug.
Not acceptable:
Documentation/process/submitting-patches.rs
"using your real name (sorry, no pseudonyms or anonymous contributions.)"
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-01-16 17:35 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-01-15 13:33 [PATCH] mm: do not try to migrate lru_gen if it's not associated with a memcg msizanoen1
2023-01-15 13:46 ` [PATCH v2] " msizanoen1
2023-01-15 23:13 ` Yu Zhao
2023-01-16 3:01 ` msizanoen
2023-01-16 17:09 ` David Hildenbrand
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