| Message ID | alpine.LSU.2.11.2101032056260.1093@eggly.anvils (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/memcontrol: fix warning in mem_cgroup_page_lruvec() | expand |
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com> 在 2021/1/4 下午1:03, Hugh Dickins 写道: > Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are > met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) > recently added to the inline mem_cgroup_page_lruvec(). > > An earlier attempt to place that warning, in mem_cgroup_lruvec(), had > been careful to do so after weeding out the mem_cgroup_disabled() case; > but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in > clear_pgdat_congested() and age_active_anon(). > > Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM > charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > Signed-off-by: Hugh Dickins <hughd@google.com> > --- > > include/linux/memcontrol.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 > +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 > @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ > { > struct mem_cgroup *memcg = page_memcg(page); > > - VM_WARN_ON_ONCE_PAGE(!memcg, page); > + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); > return mem_cgroup_lruvec(memcg, pgdat); > } > >
On 01/03/21 at 09:03pm, Hugh Dickins wrote: > Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are > met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) > recently added to the inline mem_cgroup_page_lruvec(). > > An earlier attempt to place that warning, in mem_cgroup_lruvec(), had > been careful to do so after weeding out the mem_cgroup_disabled() case; > but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in > clear_pgdat_congested() and age_active_anon(). > > Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM > charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > Signed-off-by: Hugh Dickins <hughd@google.com> > --- > > include/linux/memcontrol.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 > +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 > @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ > { > struct mem_cgroup *memcg = page_memcg(page); > > - VM_WARN_ON_ONCE_PAGE(!memcg, page); > + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); > return mem_cgroup_lruvec(memcg, pgdat); Thanks for fixing this. We also encountered this issue in kdump kernel with the mainline 5.10 kernel since 'cgroup_disable=memory' is added. Reviewed-by: Baoquan He <bhe@redhat.com>
Hugh Dickins writes: >Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are >met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) >recently added to the inline mem_cgroup_page_lruvec(). > >An earlier attempt to place that warning, in mem_cgroup_lruvec(), had >been careful to do so after weeding out the mem_cgroup_disabled() case; >but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in >clear_pgdat_congested() and age_active_anon(). > >Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM >charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). > >Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") >Signed-off-by: Hugh Dickins <hughd@google.com> Thanks. Acked-by: Chris Down <chris@chrisdown.name>
On Wed, 6 Jan 2021 14:49:35 +0800 Baoquan He <bhe@redhat.com> wrote: > > --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 > > +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 > > @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ > > { > > struct mem_cgroup *memcg = page_memcg(page); > > > > - VM_WARN_ON_ONCE_PAGE(!memcg, page); > > + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); > > return mem_cgroup_lruvec(memcg, pgdat); > > Thanks for fixing this. We also encountered this issue in kdump kernel > with the mainline 5.10 kernel since 'cgroup_disable=memory' is added. Thanks - I added the cc:stable.
On Wed, 6 Jan 2021 14:49:35 +0800 Baoquan He <bhe@redhat.com> wrote: > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > > ... > > Thanks for fixing this. We also encountered this issue in kdump kernel > with the mainline 5.10 kernel since 'cgroup_disable=memory' is added. Wait. 9a1ac2288cf1 isn't present in 5.10?
On 01/06/21 at 11:35am, Andrew Morton wrote: > On Wed, 6 Jan 2021 14:49:35 +0800 Baoquan He <bhe@redhat.com> wrote: > > > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > > > > ... > > > > Thanks for fixing this. We also encountered this issue in kdump kernel > > with the mainline 5.10 kernel since 'cgroup_disable=memory' is added. > > Wait. 9a1ac2288cf1 isn't present in 5.10? > Yes, just checked, commit 9a1ac2288cf1 was merged in 5.11-rc1, not in 5.10.0. Seems Redhat CKI doesn't treat the kernel release correctly, it calls all kernel 5.11-rcx as 5.10.0. Sorry for the confusion, I will send mail to them to change this. I got the failure report from redhat's CKI test, the kernel repo is as below, but the subject of failure report and 'uname -r' told it's 5.10.0. Kernel repo: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git Commit: 58cf05f597b0 - Merge tag 'sound-fix-5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
On 1/4/21 6:03 AM, Hugh Dickins wrote: > Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are > met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) > recently added to the inline mem_cgroup_page_lruvec(). > > An earlier attempt to place that warning, in mem_cgroup_lruvec(), had > been careful to do so after weeding out the mem_cgroup_disabled() case; > but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in > clear_pgdat_congested() and age_active_anon(). > > Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM > charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > > include/linux/memcontrol.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 > +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 > @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ > { > struct mem_cgroup *memcg = page_memcg(page); > > - VM_WARN_ON_ONCE_PAGE(!memcg, page); > + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); Nit: I would reverse the order of conditions as mem_cgroup_disabled() is either "return true" or a static key. Not that it matters too much on DEBUG_VM configs... > return mem_cgroup_lruvec(memcg, pgdat); > } > >
On Thu, 7 Jan 2021, Vlastimil Babka wrote: > On 1/4/21 6:03 AM, Hugh Dickins wrote: > > Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are > > met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) > > recently added to the inline mem_cgroup_page_lruvec(). > > > > An earlier attempt to place that warning, in mem_cgroup_lruvec(), had > > been careful to do so after weeding out the mem_cgroup_disabled() case; > > but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in > > clear_pgdat_congested() and age_active_anon(). > > > > Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM > > charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). > > > > Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") > > Signed-off-by: Hugh Dickins <hughd@google.com> > > Acked-by: Vlastimil Babka <vbabka@suse.cz> Thanks. > > > --- > > > > include/linux/memcontrol.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > --- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 > > +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 > > @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ > > { > > struct mem_cgroup *memcg = page_memcg(page); > > > > - VM_WARN_ON_ONCE_PAGE(!memcg, page); > > + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); > > Nit: I would reverse the order of conditions as mem_cgroup_disabled() is either > "return true" or a static key. Not that it matters too much on DEBUG_VM configs... tl;dr I'm going to leave the patch as is. You are certainly right that I was forgetting the static-key-ness of mem_cgroup_disabled() when I put the tests that way round: I was thinking of the already-in-a-register-ness of "memcg"; but had also not realized that page_memcg() just did an "&", so condition bits nicely set already. And I think you are right in principle, that the tests should be better the way you suggest, when static key is in use - in the (unusual) mem_cgroup_disabled() case, though not in the usual enabled case. I refuse to confess how many hours I've spent poring over "objdump -ld"s of lock_page_lruvec_irqsave(), and comparing with how it is patched when the kernel is booted with "cgroup_disable=memory". But I have seen builds where my way round worked out better than yours, for both the enabled and disabled cases (SUSE gcc 9.3.1 was good, in the config I was trying on it); and builds where disabled was treated rather poorly my way (with external call to mem_cgroup_disabled() from lock_page_lruvec() and lock_page_lruvec_irqsave(), but inlined into lock_page_lruvec_irq() - go figure! - with SUSE gcc 10.2.1). I suspect a lot depends on what inlining is done, and on that prior page_memcg() doing its "&", and the second mem_cgroup_disabled() which follows immediately in mem_cgroup_lruvec(): different compilers will make different choices, favouring one or the other ordering. I've grown rather tired of it all (and discovered on the way that static keys depend on CONFIG_JUMP_LABEL=y, which I didn't have in a config I've carried forward through "make oldconfig"s for years - thanks); but not found a decisive reason to change the patch. Hugh > > > return mem_cgroup_lruvec(memcg, pgdat); > > } > > > >
--- 5.11-rc2/include/linux/memcontrol.h 2020-12-27 20:39:36.751923135 -0800 +++ linux/include/linux/memcontrol.h 2021-01-03 19:38:24.822978559 -0800 @@ -665,7 +665,7 @@ static inline struct lruvec *mem_cgroup_ { struct mem_cgroup *memcg = page_memcg(page); - VM_WARN_ON_ONCE_PAGE(!memcg, page); + VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page); return mem_cgroup_lruvec(memcg, pgdat); }
Boot a CONFIG_MEMCG=y kernel with "cgroup_disabled=memory" and you are met by a series of warnings from the VM_WARN_ON_ONCE_PAGE(!memcg, page) recently added to the inline mem_cgroup_page_lruvec(). An earlier attempt to place that warning, in mem_cgroup_lruvec(), had been careful to do so after weeding out the mem_cgroup_disabled() case; but was itself invalid because of the mem_cgroup_lruvec(NULL, pgdat) in clear_pgdat_congested() and age_active_anon(). Warning in mem_cgroup_page_lruvec() was once useful in detecting a KSM charge bug, so may be worth keeping: but skip if mem_cgroup_disabled(). Fixes: 9a1ac2288cf1 ("mm/memcontrol:rewrite mem_cgroup_page_lruvec()") Signed-off-by: Hugh Dickins <hughd@google.com> --- include/linux/memcontrol.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)