| Message ID | 20181029215123.17830-1-guro@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: handle no memcg case in memcg_kmem_charge() properly | expand |
On Mon, Oct 29, 2018 at 2:52 PM Roman Gushchin <guro@fb.com> wrote: > > Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 > ("mm: rework memcg kernel stack accounting") on a system with > "cgroup_disable=memory" boot option: the system panics with the > following stack trace: > > [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 > [0.929317] PGD 0 P4D 0 > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000000 > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 00000000000000f8 > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37a40 > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000020 > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1ec60 > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:0000000000000000 > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760ef0 > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [0.942110] PKRU: 55555554 > [0.942412] Call Trace: > [0.942673] try_charge+0xcb/0x780 > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > [0.944396] copy_process.part.41+0x1ca/0x2070 > [0.944853] ? get_acl+0x1a/0x120 > [0.945200] ? shmem_tmpfile+0x90/0x90 > [0.945596] _do_fork+0xd7/0x3d0 > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > [0.946421] do_syscall_64+0x5a/0x180 > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The problem occurs because get_mem_cgroup_from_current() returns > the NULL pointer if memory controller is disabled. Let's check > if this is a case at the beginning of memcg_kmem_charge() and > just return 0 if mem_cgroup_disabled() returns true. This is how > we handle this case in many other places in the memory controller > code. > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > Reported-by: Mike Galbraith <efault@gmx.de> > Signed-off-by: Roman Gushchin <guro@fb.com> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > --- > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 54920cbc46bf..6e1469b80cb7 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order) > struct mem_cgroup *memcg; > int ret = 0; > > - if (memcg_kmem_bypass()) > + if (mem_cgroup_disabled() || memcg_kmem_bypass()) > return 0; > Why not check memcg_kmem_enabled() before calling memcg_kmem_charge() in memcg_charge_kernel_stack()? > memcg = get_mem_cgroup_from_current(); > -- > 2.17.2 >
On Mon, 2018-10-29 at 17:50 -0700, Shakeel Butt wrote: > On Mon, Oct 29, 2018 at 2:52 PM Roman Gushchin <guro@fb.com> wrote: > > > > Mike Galbraith reported a regression caused by the commit > > 9b6f7e163cd0 > > ("mm: rework memcg kernel stack accounting") on a system with > > "cgroup_disable=memory" boot option: the system panics with the > > following stack trace: > > > > [0.928542] BUG: unable to handle kernel NULL pointer dereference > > at 00000000000000f8 > > [0.929317] PGD 0 P4D 0 > > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0- > > preempt+ #410 > > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > > BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff > > 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: > > 0000000000000000 > > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: > > 00000000000000f8 > > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: > > ffff99ff7cd37a40 > > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: > > 0000000000000020 > > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: > > ffff99ff7da1ec60 > > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) > > knlGS:0000000000000000 > > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: > > 0000000000760ef0 > > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: > > 0000000000000000 > > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: > > 0000000000000400 > > [0.942110] PKRU: 55555554 > > [0.942412] Call Trace: > > [0.942673] try_charge+0xcb/0x780 > > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > > [0.944396] copy_process.part.41+0x1ca/0x2070 > > [0.944853] ? get_acl+0x1a/0x120 > > [0.945200] ? shmem_tmpfile+0x90/0x90 > > [0.945596] _do_fork+0xd7/0x3d0 > > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > > [0.946421] do_syscall_64+0x5a/0x180 > > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The problem occurs because get_mem_cgroup_from_current() returns > > the NULL pointer if memory controller is disabled. Let's check > > if this is a case at the beginning of memcg_kmem_charge() and > > just return 0 if mem_cgroup_disabled() returns true. This is how > > we handle this case in many other places in the memory controller > > code. > > > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > > Reported-by: Mike Galbraith <efault@gmx.de> > > Signed-off-by: Roman Gushchin <guro@fb.com> > > Cc: Michal Hocko <mhocko@kernel.org> > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > --- > > mm/memcontrol.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > index 54920cbc46bf..6e1469b80cb7 100644 > > --- a/mm/memcontrol.c > > +++ b/mm/memcontrol.c > > @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, > > gfp_t gfp, int order) > > struct mem_cgroup *memcg; > > int ret = 0; > > > > - if (memcg_kmem_bypass()) > > + if (mem_cgroup_disabled() || memcg_kmem_bypass()) > > return 0; > > > > Why not check memcg_kmem_enabled() before calling memcg_kmem_charge() > in memcg_charge_kernel_stack()? Check Roman's backtrace again. The function memcg_charge_kernel_stack() is not in it. That is why it is generally better to check in the called function, rather than add a check to every call site (and maybe miss one or two). Acked-by: Rik van Riel <riel@surriel.com>
On Mon, Oct 29, 2018 at 6:01 PM Rik van Riel <riel@surriel.com> wrote: > > On Mon, 2018-10-29 at 17:50 -0700, Shakeel Butt wrote: > > On Mon, Oct 29, 2018 at 2:52 PM Roman Gushchin <guro@fb.com> wrote: > > > > > > Mike Galbraith reported a regression caused by the commit > > > 9b6f7e163cd0 > > > ("mm: rework memcg kernel stack accounting") on a system with > > > "cgroup_disable=memory" boot option: the system panics with the > > > following stack trace: > > > > > > [0.928542] BUG: unable to handle kernel NULL pointer dereference > > > at 00000000000000f8 > > > [0.929317] PGD 0 P4D 0 > > > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > > > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0- > > > preempt+ #410 > > > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), > > > BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > > > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > > > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff > > > 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > > > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > > > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: > > > 0000000000000000 > > > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: > > > 00000000000000f8 > > > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: > > > ffff99ff7cd37a40 > > > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: > > > 0000000000000020 > > > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: > > > ffff99ff7da1ec60 > > > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) > > > knlGS:0000000000000000 > > > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: > > > 0000000000760ef0 > > > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: > > > 0000000000000000 > > > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: > > > 0000000000000400 > > > [0.942110] PKRU: 55555554 > > > [0.942412] Call Trace: > > > [0.942673] try_charge+0xcb/0x780 > > > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > > > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > > > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > > > [0.944396] copy_process.part.41+0x1ca/0x2070 > > > [0.944853] ? get_acl+0x1a/0x120 > > > [0.945200] ? shmem_tmpfile+0x90/0x90 > > > [0.945596] _do_fork+0xd7/0x3d0 > > > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > > > [0.946421] do_syscall_64+0x5a/0x180 > > > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > > > The problem occurs because get_mem_cgroup_from_current() returns > > > the NULL pointer if memory controller is disabled. Let's check > > > if this is a case at the beginning of memcg_kmem_charge() and > > > just return 0 if mem_cgroup_disabled() returns true. This is how > > > we handle this case in many other places in the memory controller > > > code. > > > > > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > > > Reported-by: Mike Galbraith <efault@gmx.de> > > > Signed-off-by: Roman Gushchin <guro@fb.com> > > > Cc: Michal Hocko <mhocko@kernel.org> > > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > --- > > > mm/memcontrol.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > > > index 54920cbc46bf..6e1469b80cb7 100644 > > > --- a/mm/memcontrol.c > > > +++ b/mm/memcontrol.c > > > @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, > > > gfp_t gfp, int order) > > > struct mem_cgroup *memcg; > > > int ret = 0; > > > > > > - if (memcg_kmem_bypass()) > > > + if (mem_cgroup_disabled() || memcg_kmem_bypass()) > > > return 0; > > > > > > > Why not check memcg_kmem_enabled() before calling memcg_kmem_charge() > > in memcg_charge_kernel_stack()? > > Check Roman's backtrace again. The function > memcg_charge_kernel_stack() is not in it. > It got inlined. > That is why it is generally better to check > in the called function, rather than add a > check to every call site (and maybe miss one > or two). > I think the reason the check was at the call site was not to introduce jmp/call in the allocation hot path for processes in the root memcg. I don't have any strong preference but we should be persistent i.e. checks at call site for all or check in the called function for all. Shakeel
On Mon 29-10-18 21:51:55, Roman Gushchin wrote: > Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 > ("mm: rework memcg kernel stack accounting") on a system with > "cgroup_disable=memory" boot option: the system panics with the > following stack trace: > > [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 > [0.929317] PGD 0 P4D 0 > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000000 > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 00000000000000f8 > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37a40 > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000020 > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1ec60 > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:0000000000000000 > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760ef0 > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [0.942110] PKRU: 55555554 > [0.942412] Call Trace: > [0.942673] try_charge+0xcb/0x780 > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > [0.944396] copy_process.part.41+0x1ca/0x2070 > [0.944853] ? get_acl+0x1a/0x120 > [0.945200] ? shmem_tmpfile+0x90/0x90 > [0.945596] _do_fork+0xd7/0x3d0 > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > [0.946421] do_syscall_64+0x5a/0x180 > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The problem occurs because get_mem_cgroup_from_current() returns > the NULL pointer if memory controller is disabled. Let's check > if this is a case at the beginning of memcg_kmem_charge() and > just return 0 if mem_cgroup_disabled() returns true. This is how > we handle this case in many other places in the memory controller > code. > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > Reported-by: Mike Galbraith <efault@gmx.de> > Signed-off-by: Roman Gushchin <guro@fb.com> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > Cc: Andrew Morton <akpm@linux-foundation.org> I tend to agree with Shakeel that consistency with the other caller would be less confusing. I would split the function to __memcg_kmem_charge without any checks and call it from __alloc_pages_nodemask and add the check to memcg_kmem_charge. This would be less confusing I guess. Something for a follow up clean up though. Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 54920cbc46bf..6e1469b80cb7 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order) > struct mem_cgroup *memcg; > int ret = 0; > > - if (memcg_kmem_bypass()) > + if (mem_cgroup_disabled() || memcg_kmem_bypass()) > return 0; > > memcg = get_mem_cgroup_from_current(); > -- > 2.17.2
On Tue, Oct 30, 2018 at 07:12:49AM +0100, Michal Hocko wrote: > On Mon 29-10-18 21:51:55, Roman Gushchin wrote: > > Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 > > ("mm: rework memcg kernel stack accounting") on a system with > > "cgroup_disable=memory" boot option: the system panics with the > > following stack trace: > > > > [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 > > [0.929317] PGD 0 P4D 0 > > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 > > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000000 > > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 00000000000000f8 > > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37a40 > > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000020 > > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1ec60 > > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:0000000000000000 > > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760ef0 > > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > [0.942110] PKRU: 55555554 > > [0.942412] Call Trace: > > [0.942673] try_charge+0xcb/0x780 > > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > > [0.944396] copy_process.part.41+0x1ca/0x2070 > > [0.944853] ? get_acl+0x1a/0x120 > > [0.945200] ? shmem_tmpfile+0x90/0x90 > > [0.945596] _do_fork+0xd7/0x3d0 > > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > > [0.946421] do_syscall_64+0x5a/0x180 > > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The problem occurs because get_mem_cgroup_from_current() returns > > the NULL pointer if memory controller is disabled. Let's check > > if this is a case at the beginning of memcg_kmem_charge() and > > just return 0 if mem_cgroup_disabled() returns true. This is how > > we handle this case in many other places in the memory controller > > code. > > > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > > Reported-by: Mike Galbraith <efault@gmx.de> > > Signed-off-by: Roman Gushchin <guro@fb.com> > > Cc: Michal Hocko <mhocko@kernel.org> > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > > Cc: Andrew Morton <akpm@linux-foundation.org> > > I tend to agree with Shakeel that consistency with the other caller > would be less confusing. I totally agree that consistency is a thing here (and everywhere), however using memcg_kmem_enabled() here is not consistent at all. memcg_kmem_enabled() is tight to the slab allocation accounting, but here we have a different type of allocation: we actually charge an area preallocated using vmalloc. > I would split the function to __memcg_kmem_charge > without any checks and call it from __alloc_pages_nodemask and add the > check to memcg_kmem_charge. This would be less confusing I guess. > Something for a follow up clean up though. Sure. Alternatively, we can check the pointer returned by get_mem_cgroup_from_current() in memcg_kmem_charge(). Anyway, let's postpone this clean up a bit, now the main goal is to fix the panic. > Acked-by: Michal Hocko <mhocko@suse.com> Thanks! -- Andrew, can you, please, pull this patch to 4.20-rc1 or -rc2? It has been acked by Rik and Michal, and tested by Mike. Thanks!
On Tue, Oct 30, 2018 at 8:56 AM Roman Gushchin <guro@fb.com> wrote: > > On Tue, Oct 30, 2018 at 07:12:49AM +0100, Michal Hocko wrote: > > On Mon 29-10-18 21:51:55, Roman Gushchin wrote: > > > Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 > > > ("mm: rework memcg kernel stack accounting") on a system with > > > "cgroup_disable=memory" boot option: the system panics with the > > > following stack trace: > > > > > > [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 > > > [0.929317] PGD 0 P4D 0 > > > [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI > > > [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 > > > [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 > > > [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 > > > [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 > > > [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 > > > [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000000 > > > [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 00000000000000f8 > > > [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37a40 > > > [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000020 > > > [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1ec60 > > > [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:0000000000000000 > > > [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760ef0 > > > [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > [0.942110] PKRU: 55555554 > > > [0.942412] Call Trace: > > > [0.942673] try_charge+0xcb/0x780 > > > [0.943031] memcg_kmem_charge_memcg+0x28/0x80 > > > [0.943486] ? __vmalloc_node_range+0x1e4/0x280 > > > [0.943971] memcg_kmem_charge+0x8b/0x1d0 > > > [0.944396] copy_process.part.41+0x1ca/0x2070 > > > [0.944853] ? get_acl+0x1a/0x120 > > > [0.945200] ? shmem_tmpfile+0x90/0x90 > > > [0.945596] _do_fork+0xd7/0x3d0 > > > [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c > > > [0.946421] do_syscall_64+0x5a/0x180 > > > [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > > > The problem occurs because get_mem_cgroup_from_current() returns > > > the NULL pointer if memory controller is disabled. Let's check > > > if this is a case at the beginning of memcg_kmem_charge() and > > > just return 0 if mem_cgroup_disabled() returns true. This is how > > > we handle this case in many other places in the memory controller > > > code. > > > > > > Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") > > > Reported-by: Mike Galbraith <efault@gmx.de> > > > Signed-off-by: Roman Gushchin <guro@fb.com> > > > Cc: Michal Hocko <mhocko@kernel.org> > > > Cc: Johannes Weiner <hannes@cmpxchg.org> > > > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > > I tend to agree with Shakeel that consistency with the other caller > > would be less confusing. > > I totally agree that consistency is a thing here (and everywhere), > however using memcg_kmem_enabled() here is not consistent at all. > memcg_kmem_enabled() is tight to the slab allocation accounting, Not really, see __alloc_pages_nodemask() where page allocations with __GFP_ACCOUNT call memcg_kmem_charge() only if memcg_kmem_enabled(). Anyways it's a separate discussion and can be done in the followup cleanup. Shakeel
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 54920cbc46bf..6e1469b80cb7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2593,7 +2593,7 @@ int memcg_kmem_charge(struct page *page, gfp_t gfp, int order) struct mem_cgroup *memcg; int ret = 0; - if (memcg_kmem_bypass()) + if (mem_cgroup_disabled() || memcg_kmem_bypass()) return 0; memcg = get_mem_cgroup_from_current();
Mike Galbraith reported a regression caused by the commit 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") on a system with "cgroup_disable=memory" boot option: the system panics with the following stack trace: [0.928542] BUG: unable to handle kernel NULL pointer dereference at 00000000000000f8 [0.929317] PGD 0 P4D 0 [0.929573] Oops: 0002 [#1] PREEMPT SMP PTI [0.929984] CPU: 0 PID: 1 Comm: systemd Not tainted 4.19.0-preempt+ #410 [0.930637] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20180531_142017-buildhw-08.phx2.fed4 [0.931862] RIP: 0010:page_counter_try_charge+0x22/0xc0 [0.932376] Code: 41 5d c3 c3 0f 1f 40 00 0f 1f 44 00 00 48 85 ff 0f 84 a7 00 00 00 41 56 48 89 f8 49 89 fe 49 [0.934283] RSP: 0018:ffffacf68031fcb8 EFLAGS: 00010202 [0.934826] RAX: 00000000000000f8 RBX: 0000000000000000 RCX: 0000000000000000 [0.935558] RDX: ffffacf68031fd08 RSI: 0000000000000020 RDI: 00000000000000f8 [0.936288] RBP: 0000000000000001 R08: 8000000000000063 R09: ffff99ff7cd37a40 [0.937021] R10: ffffacf68031fed0 R11: 0000000000200000 R12: 0000000000000020 [0.937749] R13: ffffacf68031fd08 R14: 00000000000000f8 R15: ffff99ff7da1ec60 [0.938486] FS: 00007fc2140bb280(0000) GS:ffff99ff7da00000(0000) knlGS:0000000000000000 [0.939311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [0.939905] CR2: 00000000000000f8 CR3: 0000000012dc8002 CR4: 0000000000760ef0 [0.940638] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [0.941366] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [0.942110] PKRU: 55555554 [0.942412] Call Trace: [0.942673] try_charge+0xcb/0x780 [0.943031] memcg_kmem_charge_memcg+0x28/0x80 [0.943486] ? __vmalloc_node_range+0x1e4/0x280 [0.943971] memcg_kmem_charge+0x8b/0x1d0 [0.944396] copy_process.part.41+0x1ca/0x2070 [0.944853] ? get_acl+0x1a/0x120 [0.945200] ? shmem_tmpfile+0x90/0x90 [0.945596] _do_fork+0xd7/0x3d0 [0.945934] ? trace_hardirqs_off_thunk+0x1a/0x1c [0.946421] do_syscall_64+0x5a/0x180 [0.946798] entry_SYSCALL_64_after_hwframe+0x49/0xbe The problem occurs because get_mem_cgroup_from_current() returns the NULL pointer if memory controller is disabled. Let's check if this is a case at the beginning of memcg_kmem_charge() and just return 0 if mem_cgroup_disabled() returns true. This is how we handle this case in many other places in the memory controller code. Fixes: 9b6f7e163cd0 ("mm: rework memcg kernel stack accounting") Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Roman Gushchin <guro@fb.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)