* [RFC][PATCH 0/3] pgtable bytes mis-accounting v2
@ 2018-10-15 16:42 Martin Schwidefsky
2018-10-15 16:42 ` [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded Martin Schwidefsky
` (2 more replies)
0 siblings, 3 replies; 19+ messages in thread
From: Martin Schwidefsky @ 2018-10-15 16:42 UTC (permalink / raw)
To: Li Wang, Guenter Roeck, Janosch Frank
Cc: Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM,
Martin Schwidefsky
Greetings,
the first test patch to fix the pgtable_bytes mis-accounting on s390
still had a few problems. For one it didn't work for x86 ..
Changes v1 -> v2:
- Split the patch into three parts, one patch to add the mm_pxd_folded
helpers, one patch to use to the helpers in mm_[dec|inc]_nr_[pmds|puds]
and finally the fix for s390.
- Drop the use of __is_defined, it does not work with the
__PAGETABLE_PxD_FOLDED defines
- Do not change the basic #ifdef'ery in mm.h, just add the calls
to mm_pxd_folded to the pgtable_bytes accounting functions. This
fixes the compile error on alpha (and potentially on other archs).
Martin Schwidefsky (3):
mm: introduce mm_[p4d|pud|pmd]_folded
mm: add mm_pxd_folded checks to pgtable_bytes accounting functions
s390/mm: fix mis-accounting of pgtable_bytes
arch/s390/include/asm/mmu_context.h | 5 ----
arch/s390/include/asm/pgalloc.h | 6 ++---
arch/s390/include/asm/pgtable.h | 18 ++++++++++++++
arch/s390/include/asm/tlb.h | 6 ++---
include/linux/mm.h | 48 +++++++++++++++++++++++++++++++++++++
5 files changed, 72 insertions(+), 11 deletions(-)
--
2.16.4
^ permalink raw reply [flat|nested] 19+ messages in thread* [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded 2018-10-15 16:42 [RFC][PATCH 0/3] pgtable bytes mis-accounting v2 Martin Schwidefsky @ 2018-10-15 16:42 ` Martin Schwidefsky 2018-10-31 9:02 ` Kirill A. Shutemov 2018-10-15 16:42 ` [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions Martin Schwidefsky 2018-10-15 16:42 ` [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes Martin Schwidefsky 2 siblings, 1 reply; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-15 16:42 UTC (permalink / raw) To: Li Wang, Guenter Roeck, Janosch Frank Cc: Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM, Martin Schwidefsky Add three architecture overrideable function to test if the p4d, pud, or pmd layer of a page table is folded or not. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --- include/linux/mm.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 0416a7204be3..d1029972541c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -105,6 +105,46 @@ extern int mmap_rnd_compat_bits __read_mostly; #define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) #endif +/* + * On some architectures it depends on the mm if the p4d/pud or pmd + * layer of the page table hierarchy is folded or not. + */ +#ifndef mm_p4d_folded +#define mm_p4d_folded(mm) mm_p4d_folded(mm) +static inline bool mm_p4d_folded(struct mm_struct *mm) +{ +#ifdef __PAGETABLE_P4D_FOLDED + return 1; +#else + return 0; +#endif +} +#endif + +#ifndef mm_pud_folded +#define mm_pud_folded(mm) mm_pud_folded(mm) +static inline bool mm_pud_folded(struct mm_struct *mm) +{ +#ifdef __PAGETABLE_PUD_FOLDED + return 1; +#else + return 0; +#endif +} +#endif + +#ifndef mm_pmd_folded +#define mm_pmd_folded(mm) mm_pmd_folded(mm) +static inline bool mm_pmd_folded(struct mm_struct *mm) +{ +#ifdef __PAGETABLE_PMD_FOLDED + return 1; +#else + return 0; +#endif +} +#endif + /* * Default maximum number of active map areas, this limits the number of vmas * per mm struct. Users can overwrite this number by sysctl but there is a -- 2.16.4 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded 2018-10-15 16:42 ` [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded Martin Schwidefsky @ 2018-10-31 9:02 ` Kirill A. Shutemov 2018-10-31 9:35 ` Martin Schwidefsky 0 siblings, 1 reply; 19+ messages in thread From: Kirill A. Shutemov @ 2018-10-31 9:02 UTC (permalink / raw) To: Martin Schwidefsky Cc: Li Wang, Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Mon, Oct 15, 2018 at 06:42:37PM +0200, Martin Schwidefsky wrote: > Add three architecture overrideable function to test if the > p4d, pud, or pmd layer of a page table is folded or not. > > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> > --- > include/linux/mm.h | 40 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 40 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0416a7204be3..d1029972541c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h Shouldn't it be somewhere in asm-generic/pgtable*? > @@ -105,6 +105,46 @@ extern int mmap_rnd_compat_bits __read_mostly; > #define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) > #endif > > +/* > + * On some architectures it depends on the mm if the p4d/pud or pmd > + * layer of the page table hierarchy is folded or not. > + */ > +#ifndef mm_p4d_folded > +#define mm_p4d_folded(mm) mm_p4d_folded(mm) Do we need to define it in generic header? > +static inline bool mm_p4d_folded(struct mm_struct *mm) > +{ > +#ifdef __PAGETABLE_P4D_FOLDED > + return 1; > +#else > + return 0; > +#endif Maybe return __is_defined(__PAGETABLE_P4D_FOLDED); ? -- Kirill A. Shutemov ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded 2018-10-31 9:02 ` Kirill A. Shutemov @ 2018-10-31 9:35 ` Martin Schwidefsky 2018-10-31 9:48 ` Kirill A. Shutemov 0 siblings, 1 reply; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-31 9:35 UTC (permalink / raw) To: Kirill A. Shutemov Cc: Li Wang, Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Wed, 31 Oct 2018 12:02:55 +0300 "Kirill A. Shutemov" <kirill@shutemov.name> wrote: > On Mon, Oct 15, 2018 at 06:42:37PM +0200, Martin Schwidefsky wrote: > > Add three architecture overrideable function to test if the > > p4d, pud, or pmd layer of a page table is folded or not. > > > > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> > > --- > > include/linux/mm.h | 40 ++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 40 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 0416a7204be3..d1029972541c 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > Shouldn't it be somewhere in asm-generic/pgtable*? If you prefer the definitions in asm-generic that is fine with me. I'll give it a try to see if it still compiles. > > @@ -105,6 +105,46 @@ extern int mmap_rnd_compat_bits __read_mostly; > > #define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) > > #endif > > > > +/* > > + * On some architectures it depends on the mm if the p4d/pud or pmd > > + * layer of the page table hierarchy is folded or not. > > + */ > > +#ifndef mm_p4d_folded > > +#define mm_p4d_folded(mm) mm_p4d_folded(mm) > > Do we need to define it in generic header? That is true, it should work without the #define in the generic header. > > +static inline bool mm_p4d_folded(struct mm_struct *mm) > > +{ > > +#ifdef __PAGETABLE_P4D_FOLDED > > + return 1; > > +#else > > + return 0; > > +#endif > > Maybe > return __is_defined(__PAGETABLE_P4D_FOLDED); > > ? I have tried that, doesn't work. The reason is that the __PAGETABLE_xxx_FOLDED defines to not have a value. #define __PAGETABLE_P4D_FOLDED #define __PAGETABLE_PMD_FOLDED #define __PAGETABLE_PUD_FOLDED While the definition of CONFIG_xxx symbols looks like this #define CONFIG_xxx 1 The __is_defined needs the value for the __take_second_arg trick. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded 2018-10-31 9:35 ` Martin Schwidefsky @ 2018-10-31 9:48 ` Kirill A. Shutemov 0 siblings, 0 replies; 19+ messages in thread From: Kirill A. Shutemov @ 2018-10-31 9:48 UTC (permalink / raw) To: Martin Schwidefsky Cc: Li Wang, Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Wed, Oct 31, 2018 at 10:35:36AM +0100, Martin Schwidefsky wrote: > > Maybe > > return __is_defined(__PAGETABLE_P4D_FOLDED); > > > > ? > > I have tried that, doesn't work. The reason is that the > __PAGETABLE_xxx_FOLDED defines to not have a value. > > #define __PAGETABLE_P4D_FOLDED > #define __PAGETABLE_PMD_FOLDED > #define __PAGETABLE_PUD_FOLDED > > While the definition of CONFIG_xxx symbols looks like this > > #define CONFIG_xxx 1 > > The __is_defined needs the value for the __take_second_arg trick. I guess this is easily fixable :) -- Kirill A. Shutemov ^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions 2018-10-15 16:42 [RFC][PATCH 0/3] pgtable bytes mis-accounting v2 Martin Schwidefsky 2018-10-15 16:42 ` [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded Martin Schwidefsky @ 2018-10-15 16:42 ` Martin Schwidefsky 2018-10-31 9:04 ` Kirill A. Shutemov 2018-10-15 16:42 ` [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes Martin Schwidefsky 2 siblings, 1 reply; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-15 16:42 UTC (permalink / raw) To: Li Wang, Guenter Roeck, Janosch Frank Cc: Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM, Martin Schwidefsky The common mm code calls mm_dec_nr_pmds() and mm_dec_nr_puds() in free_pgtables() if the address range spans a full pud or pmd. If mm_dec_nr_puds/mm_dec_nr_pmds are non-empty due to configuration settings they blindly subtract the size of the pmd or pud table from pgtable_bytes even if the pud or pmd page table layer is folded. Add explicit mm_[pmd|pud]_folded checks to the four pgtable_bytes accounting functions mm_inc_nr_puds, mm_inc_nr_pmds, mm_dec_nr_puds and mm_dec_nr_pmds. As the check for folded page tables can be overwritten by the architecture, this allows to keep a correct pgtable_bytes value for platforms that use a dynamic number of page table levels. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --- include/linux/mm.h | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index d1029972541c..67f55c71e59a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1764,11 +1764,15 @@ int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address); static inline void mm_inc_nr_puds(struct mm_struct *mm) { + if (mm_pud_folded(mm)) + return; atomic_long_add(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); } static inline void mm_dec_nr_puds(struct mm_struct *mm) { + if (mm_pud_folded(mm)) + return; atomic_long_sub(PTRS_PER_PUD * sizeof(pud_t), &mm->pgtables_bytes); } #endif @@ -1788,11 +1792,15 @@ int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address); static inline void mm_inc_nr_pmds(struct mm_struct *mm) { + if (mm_pmd_folded(mm)) + return; atomic_long_add(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); } static inline void mm_dec_nr_pmds(struct mm_struct *mm) { + if (mm_pmd_folded(mm)) + return; atomic_long_sub(PTRS_PER_PMD * sizeof(pmd_t), &mm->pgtables_bytes); } #endif -- 2.16.4 ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions 2018-10-15 16:42 ` [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions Martin Schwidefsky @ 2018-10-31 9:04 ` Kirill A. Shutemov 0 siblings, 0 replies; 19+ messages in thread From: Kirill A. Shutemov @ 2018-10-31 9:04 UTC (permalink / raw) To: Martin Schwidefsky Cc: Li Wang, Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Mon, Oct 15, 2018 at 06:42:38PM +0200, Martin Schwidefsky wrote: > The common mm code calls mm_dec_nr_pmds() and mm_dec_nr_puds() > in free_pgtables() if the address range spans a full pud or pmd. > If mm_dec_nr_puds/mm_dec_nr_pmds are non-empty due to configuration > settings they blindly subtract the size of the pmd or pud table from > pgtable_bytes even if the pud or pmd page table layer is folded. > > Add explicit mm_[pmd|pud]_folded checks to the four pgtable_bytes > accounting functions mm_inc_nr_puds, mm_inc_nr_pmds, mm_dec_nr_puds > and mm_dec_nr_pmds. As the check for folded page tables can be > overwritten by the architecture, this allows to keep a correct > pgtable_bytes value for platforms that use a dynamic number of > page table levels. > > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Looks fine to me. Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> -- Kirill A. Shutemov ^ permalink raw reply [flat|nested] 19+ messages in thread
* [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-10-15 16:42 [RFC][PATCH 0/3] pgtable bytes mis-accounting v2 Martin Schwidefsky 2018-10-15 16:42 ` [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded Martin Schwidefsky 2018-10-15 16:42 ` [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions Martin Schwidefsky @ 2018-10-15 16:42 ` Martin Schwidefsky [not found] ` <CAEemH2cHNFsiDqPF32K6TNn-XoXCRT0wP4ccAeah4bKHt=FKFA@mail.gmail.com> 2 siblings, 1 reply; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-15 16:42 UTC (permalink / raw) To: Li Wang, Guenter Roeck, Janosch Frank Cc: Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM, Martin Schwidefsky In case a fork or a clone system fails in copy_process and the error handling does the mmput() at the bad_fork_cleanup_mm label, the following warning messages will appear on the console: BUG: non-zero pgtables_bytes on freeing mm: 16384 The reason for that is the tricks we play with mm_inc_nr_puds() and mm_inc_nr_pmds() in init_new_context(). A normal 64-bit process has 3 levels of page table, the p4d level and the pud level are folded. On process termination the free_pud_range() function in mm/memory.c will subtract 16KB from pgtable_bytes with a mm_dec_nr_puds() call, but there actually is not really a pud table. One issue with this is the fact that pgtable_bytes is usually off by a few kilobytes, but the more severe problem is that for a failed fork or clone the free_pgtables() function is not called. In this case there is no mm_dec_nr_puds() or mm_dec_nr_pmds() that go together with the mm_inc_nr_puds() and mm_inc_nr_pmds in init_new_context(). The pgtable_bytes will be off by 16384 or 32768 bytes and we get the BUG message. The message itself is purely cosmetic, but annoying. To fix this override the mm_pmd_folded, mm_pud_folded and mm_p4d_folded function to check for the true size of the address space. Reported-by: Li Wang <liwang@redhat.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --- arch/s390/include/asm/mmu_context.h | 5 ----- arch/s390/include/asm/pgalloc.h | 6 +++--- arch/s390/include/asm/pgtable.h | 18 ++++++++++++++++++ arch/s390/include/asm/tlb.h | 6 +++--- 4 files changed, 24 insertions(+), 11 deletions(-) diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h index 0717ee76885d..f1ab9420ccfb 100644 --- a/arch/s390/include/asm/mmu_context.h +++ b/arch/s390/include/asm/mmu_context.h @@ -45,8 +45,6 @@ static inline int init_new_context(struct task_struct *tsk, mm->context.asce_limit = STACK_TOP_MAX; mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | _ASCE_USER_BITS | _ASCE_TYPE_REGION3; - /* pgd_alloc() did not account this pud */ - mm_inc_nr_puds(mm); break; case -PAGE_SIZE: /* forked 5-level task, set new asce with new_mm->pgd */ @@ -62,9 +60,6 @@ static inline int init_new_context(struct task_struct *tsk, /* forked 2-level compat task, set new asce with new mm->pgd */ mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; - /* pgd_alloc() did not account this pmd */ - mm_inc_nr_pmds(mm); - mm_inc_nr_puds(mm); } crst_table_init((unsigned long *) mm->pgd, pgd_entry_type(mm)); return 0; diff --git a/arch/s390/include/asm/pgalloc.h b/arch/s390/include/asm/pgalloc.h index f0f9bcf94c03..5ee733720a57 100644 --- a/arch/s390/include/asm/pgalloc.h +++ b/arch/s390/include/asm/pgalloc.h @@ -36,11 +36,11 @@ static inline void crst_table_init(unsigned long *crst, unsigned long entry) static inline unsigned long pgd_entry_type(struct mm_struct *mm) { - if (mm->context.asce_limit <= _REGION3_SIZE) + if (mm_pmd_folded(mm)) return _SEGMENT_ENTRY_EMPTY; - if (mm->context.asce_limit <= _REGION2_SIZE) + if (mm_pud_folded(mm)) return _REGION3_ENTRY_EMPTY; - if (mm->context.asce_limit <= _REGION1_SIZE) + if (mm_p4d_folded(mm)) return _REGION2_ENTRY_EMPTY; return _REGION1_ENTRY_EMPTY; } diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 0e7cb0dc9c33..de05466ce50c 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -485,6 +485,24 @@ static inline int is_module_addr(void *addr) _REGION_ENTRY_PROTECT | \ _REGION_ENTRY_NOEXEC) +static inline bool mm_p4d_folded(struct mm_struct *mm) +{ + return mm->context.asce_limit <= _REGION1_SIZE; +} +#define mm_p4d_folded(mm) mm_p4d_folded(mm) + +static inline bool mm_pud_folded(struct mm_struct *mm) +{ + return mm->context.asce_limit <= _REGION2_SIZE; +} +#define mm_pud_folded(mm) mm_pud_folded(mm) + +static inline bool mm_pmd_folded(struct mm_struct *mm) +{ + return mm->context.asce_limit <= _REGION3_SIZE; +} +#define mm_pmd_folded(mm) mm_pmd_folded(mm) + static inline int mm_has_pgste(struct mm_struct *mm) { #ifdef CONFIG_PGSTE diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h index 457b7ba0fbb6..b31c779cf581 100644 --- a/arch/s390/include/asm/tlb.h +++ b/arch/s390/include/asm/tlb.h @@ -136,7 +136,7 @@ static inline void pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte, static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, unsigned long address) { - if (tlb->mm->context.asce_limit <= _REGION3_SIZE) + if (mm_pmd_folded(tlb->mm)) return; pgtable_pmd_page_dtor(virt_to_page(pmd)); tlb_remove_table(tlb, pmd); @@ -152,7 +152,7 @@ static inline void pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd, static inline void p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d, unsigned long address) { - if (tlb->mm->context.asce_limit <= _REGION1_SIZE) + if (mm_p4d_folded(tlb->mm)) return; tlb_remove_table(tlb, p4d); } @@ -167,7 +167,7 @@ static inline void p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d, static inline void pud_free_tlb(struct mmu_gather *tlb, pud_t *pud, unsigned long address) { - if (tlb->mm->context.asce_limit <= _REGION2_SIZE) + if (mm_pud_folded(tlb->mm)) return; tlb_remove_table(tlb, pud); } -- 2.16.4 ^ permalink raw reply related [flat|nested] 19+ messages in thread
[parent not found: <CAEemH2cHNFsiDqPF32K6TNn-XoXCRT0wP4ccAeah4bKHt=FKFA@mail.gmail.com>]
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes [not found] ` <CAEemH2cHNFsiDqPF32K6TNn-XoXCRT0wP4ccAeah4bKHt=FKFA@mail.gmail.com> @ 2018-10-31 6:31 ` Martin Schwidefsky [not found] ` <CAEemH2f2gW22PJYpVrh7p5zJyHOVRfVawJWD+kN3+8LmApePbw@mail.gmail.com> 2018-10-31 10:09 ` Heiko Carstens 0 siblings, 2 replies; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-31 6:31 UTC (permalink / raw) To: Li Wang Cc: Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Wed, 31 Oct 2018 14:18:33 +0800 Li Wang <liwang@redhat.com> wrote: > On Tue, Oct 16, 2018 at 12:42 AM, Martin Schwidefsky <schwidefsky@de.ibm.com > > wrote: > > > In case a fork or a clone system fails in copy_process and the error > > handling does the mmput() at the bad_fork_cleanup_mm label, the > > following warning messages will appear on the console: > > > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > > The reason for that is the tricks we play with mm_inc_nr_puds() and > > mm_inc_nr_pmds() in init_new_context(). > > > > A normal 64-bit process has 3 levels of page table, the p4d level and > > the pud level are folded. On process termination the free_pud_range() > > function in mm/memory.c will subtract 16KB from pgtable_bytes with a > > mm_dec_nr_puds() call, but there actually is not really a pud table. > > > > One issue with this is the fact that pgtable_bytes is usually off > > by a few kilobytes, but the more severe problem is that for a failed > > fork or clone the free_pgtables() function is not called. In this case > > there is no mm_dec_nr_puds() or mm_dec_nr_pmds() that go together with > > the mm_inc_nr_puds() and mm_inc_nr_pmds in init_new_context(). > > The pgtable_bytes will be off by 16384 or 32768 bytes and we get the > > BUG message. The message itself is purely cosmetic, but annoying. > > > > To fix this override the mm_pmd_folded, mm_pud_folded and mm_p4d_folded > > function to check for the true size of the address space. > > > > I can confirm that it works to the problem, the warning message is gone > after applying this patch on s390x. And I also done ltp syscalls/cve test > for the patch set on x86_64 arch, there has no new regression. > > Tested-by: Li Wang <liwang@redhat.com> Thanks for testing. Unfortunately Heiko reported another issue yesterday with the patch applied. This time the other way around: BUG: non-zero pgtables_bytes on freeing mm: -16384 I am trying to understand how this can happen. For now I would like to keep the patch on hold in case they need another change. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ^ permalink raw reply [flat|nested] 19+ messages in thread
[parent not found: <CAEemH2f2gW22PJYpVrh7p5zJyHOVRfVawJWD+kN3+8LmApePbw@mail.gmail.com>]
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes [not found] ` <CAEemH2f2gW22PJYpVrh7p5zJyHOVRfVawJWD+kN3+8LmApePbw@mail.gmail.com> @ 2018-10-31 6:46 ` Martin Schwidefsky 2018-10-31 9:39 ` Martin Schwidefsky 0 siblings, 1 reply; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-31 6:46 UTC (permalink / raw) To: Li Wang Cc: Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Wed, 31 Oct 2018 14:43:38 +0800 Li Wang <liwang@redhat.com> wrote: > On Wed, Oct 31, 2018 at 2:31 PM, Martin Schwidefsky <schwidefsky@de.ibm.com> > wrote: > > > On Wed, 31 Oct 2018 14:18:33 +0800 > > Li Wang <liwang@redhat.com> wrote: > > > > > On Tue, Oct 16, 2018 at 12:42 AM, Martin Schwidefsky < > > schwidefsky@de.ibm.com > > > > wrote: > > > > > > > In case a fork or a clone system fails in copy_process and the error > > > > handling does the mmput() at the bad_fork_cleanup_mm label, the > > > > following warning messages will appear on the console: > > > > > > > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > > > > > > > The reason for that is the tricks we play with mm_inc_nr_puds() and > > > > mm_inc_nr_pmds() in init_new_context(). > > > > > > > > A normal 64-bit process has 3 levels of page table, the p4d level and > > > > the pud level are folded. On process termination the free_pud_range() > > > > function in mm/memory.c will subtract 16KB from pgtable_bytes with a > > > > mm_dec_nr_puds() call, but there actually is not really a pud table. > > > > > > > > One issue with this is the fact that pgtable_bytes is usually off > > > > by a few kilobytes, but the more severe problem is that for a failed > > > > fork or clone the free_pgtables() function is not called. In this case > > > > there is no mm_dec_nr_puds() or mm_dec_nr_pmds() that go together with > > > > the mm_inc_nr_puds() and mm_inc_nr_pmds in init_new_context(). > > > > The pgtable_bytes will be off by 16384 or 32768 bytes and we get the > > > > BUG message. The message itself is purely cosmetic, but annoying. > > > > > > > > To fix this override the mm_pmd_folded, mm_pud_folded and mm_p4d_folded > > > > function to check for the true size of the address space. > > > > > > > > > > I can confirm that it works to the problem, the warning message is gone > > > after applying this patch on s390x. And I also done ltp syscalls/cve test > > > for the patch set on x86_64 arch, there has no new regression. > > > > > > Tested-by: Li Wang <liwang@redhat.com> > > > > Thanks for testing. Unfortunately Heiko reported another issue yesterday > > with the patch applied. This time the other way around: > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > Okay, the problem is still triggered by LTP/cve-2017-17052.c? No, unfortunately we do not have a simple testcase to trigger this new bug. It happened once with one of our test kernels, the path that leads to this is completely unclear. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-10-31 6:46 ` Martin Schwidefsky @ 2018-10-31 9:39 ` Martin Schwidefsky 0 siblings, 0 replies; 19+ messages in thread From: Martin Schwidefsky @ 2018-10-31 9:39 UTC (permalink / raw) To: Li Wang Cc: Guenter Roeck, Janosch Frank, Kirill A. Shutemov, Heiko Carstens, linux-kernel, Linux-MM On Wed, 31 Oct 2018 07:46:47 +0100 Martin Schwidefsky <schwidefsky@de.ibm.com> wrote: > On Wed, 31 Oct 2018 14:43:38 +0800 > Li Wang <liwang@redhat.com> wrote: > > > On Wed, Oct 31, 2018 at 2:31 PM, Martin Schwidefsky <schwidefsky@de.ibm.com> > > wrote: > > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > > > > Okay, the problem is still triggered by LTP/cve-2017-17052.c? > > No, unfortunately we do not have a simple testcase to trigger this new bug. > It happened once with one of our test kernels, the path that leads to this > is completely unclear. Ok, got it. There is a mm_inc_nr_puds(mm) missing in the s390 code: diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 76d89ee8b428..814f26520aa2 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -101,6 +101,7 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end) mm->context.asce_limit = _REGION1_SIZE; mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | _ASCE_USER_BITS | _ASCE_TYPE_REGION2; + mm_inc_nr_puds(mm); } else { crst_table_init(table, _REGION1_ENTRY_EMPTY); pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd); One of our test-cases did an upgrade of a 3-level page table. I'll update the patch and send a v3. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-10-31 6:31 ` Martin Schwidefsky [not found] ` <CAEemH2f2gW22PJYpVrh7p5zJyHOVRfVawJWD+kN3+8LmApePbw@mail.gmail.com> @ 2018-10-31 10:09 ` Heiko Carstens 2018-10-31 10:36 ` Kirill A. Shutemov 1 sibling, 1 reply; 19+ messages in thread From: Heiko Carstens @ 2018-10-31 10:09 UTC (permalink / raw) To: Kirill A. Shutemov Cc: Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: > Thanks for testing. Unfortunately Heiko reported another issue yesterday > with the patch applied. This time the other way around: > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > I am trying to understand how this can happen. For now I would like to > keep the patch on hold in case they need another change. FWIW, Kirill: is there a reason why this "BUG:" output is done with pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? That would to get more information with DEBUG_VM and / or panic_on_warn=1 set. At least for automated testing it would be nice to have such triggers. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-10-31 10:09 ` Heiko Carstens @ 2018-10-31 10:36 ` Kirill A. Shutemov 2018-11-27 7:34 ` Heiko Carstens 0 siblings, 1 reply; 19+ messages in thread From: Kirill A. Shutemov @ 2018-10-31 10:36 UTC (permalink / raw) To: Heiko Carstens Cc: Kirill A. Shutemov, Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote: > On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: > > Thanks for testing. Unfortunately Heiko reported another issue yesterday > > with the patch applied. This time the other way around: > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > I am trying to understand how this can happen. For now I would like to > > keep the patch on hold in case they need another change. > > FWIW, Kirill: is there a reason why this "BUG:" output is done with > pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? > > That would to get more information with DEBUG_VM and / or > panic_on_warn=1 set. At least for automated testing it would be nice > to have such triggers. Stack trace is not helpful there. It will always show the exit path which is useless. -- Kirill A. Shutemov ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-10-31 10:36 ` Kirill A. Shutemov @ 2018-11-27 7:34 ` Heiko Carstens 2018-11-27 8:05 ` Kirill A. Shutemov ` (2 more replies) 0 siblings, 3 replies; 19+ messages in thread From: Heiko Carstens @ 2018-11-27 7:34 UTC (permalink / raw) To: Kirill A. Shutemov Cc: Kirill A. Shutemov, Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Wed, Oct 31, 2018 at 01:36:23PM +0300, Kirill A. Shutemov wrote: > On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote: > > On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: > > > Thanks for testing. Unfortunately Heiko reported another issue yesterday > > > with the patch applied. This time the other way around: > > > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > > > I am trying to understand how this can happen. For now I would like to > > > keep the patch on hold in case they need another change. > > > > FWIW, Kirill: is there a reason why this "BUG:" output is done with > > pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? > > > > That would to get more information with DEBUG_VM and / or > > panic_on_warn=1 set. At least for automated testing it would be nice > > to have such triggers. > > Stack trace is not helpful there. It will always show the exit path which > is useless. So, even with the updated version of these patches I can flood dmesg and the console with BUG: non-zero pgtables_bytes on freeing mm: 16384 messages with this complex reproducer on s390: echo "void main(void) {}" | gcc -m31 -xc -o compat - && ./compat Besides that this needs to be fixed, I'd really like to see this changed to either a printk_once() or a WARN_ON_ONCE() within check_mm() so that an arbitrary user cannot flood the console. E.g. something like the below. If there aren't any objections, I will provide a proper patch with changelog, etc. diff --git a/kernel/fork.c b/kernel/fork.c index 07cddff89c7b..d7aeec03c57f 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) } if (mm_pgtables_bytes(mm)) - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", - mm_pgtables_bytes(mm)); + printk_once(KERN_ALERT "BUG: non-zero pgtables_bytes on freeing mm: %ld\n", + mm_pgtables_bytes(mm)); #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS VM_BUG_ON_MM(mm->pmd_huge_pte, mm); ^ permalink raw reply related [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-11-27 7:34 ` Heiko Carstens @ 2018-11-27 8:05 ` Kirill A. Shutemov 2018-11-27 8:13 ` Heiko Carstens 2018-11-27 11:47 ` Guenter Roeck 2018-11-27 14:31 ` Martin Schwidefsky 2 siblings, 1 reply; 19+ messages in thread From: Kirill A. Shutemov @ 2018-11-27 8:05 UTC (permalink / raw) To: Heiko Carstens Cc: Kirill A. Shutemov, Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Tue, Nov 27, 2018 at 08:34:12AM +0100, Heiko Carstens wrote: > On Wed, Oct 31, 2018 at 01:36:23PM +0300, Kirill A. Shutemov wrote: > > On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote: > > > On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: > > > > Thanks for testing. Unfortunately Heiko reported another issue yesterday > > > > with the patch applied. This time the other way around: > > > > > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > > > > > I am trying to understand how this can happen. For now I would like to > > > > keep the patch on hold in case they need another change. > > > > > > FWIW, Kirill: is there a reason why this "BUG:" output is done with > > > pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? > > > > > > That would to get more information with DEBUG_VM and / or > > > panic_on_warn=1 set. At least for automated testing it would be nice > > > to have such triggers. > > > > Stack trace is not helpful there. It will always show the exit path which > > is useless. > > So, even with the updated version of these patches I can flood dmesg > and the console with > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > messages with this complex reproducer on s390: > > echo "void main(void) {}" | gcc -m31 -xc -o compat - && ./compat > > Besides that this needs to be fixed, I'd really like to see this > changed to either a printk_once() or a WARN_ON_ONCE() within > check_mm() so that an arbitrary user cannot flood the console. > > E.g. something like the below. If there aren't any objections, I will > provide a proper patch with changelog, etc. > > diff --git a/kernel/fork.c b/kernel/fork.c > index 07cddff89c7b..d7aeec03c57f 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > } > > if (mm_pgtables_bytes(mm)) > - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > - mm_pgtables_bytes(mm)); > + printk_once(KERN_ALERT "BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > + mm_pgtables_bytes(mm)); You can be the first user of pr_alert_once(). Don't miss a chance! ;) -- Kirill A. Shutemov ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-11-27 8:05 ` Kirill A. Shutemov @ 2018-11-27 8:13 ` Heiko Carstens 0 siblings, 0 replies; 19+ messages in thread From: Heiko Carstens @ 2018-11-27 8:13 UTC (permalink / raw) To: Kirill A. Shutemov Cc: Kirill A. Shutemov, Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Tue, Nov 27, 2018 at 11:05:15AM +0300, Kirill A. Shutemov wrote: > > E.g. something like the below. If there aren't any objections, I will > > provide a proper patch with changelog, etc. > > > > diff --git a/kernel/fork.c b/kernel/fork.c > > index 07cddff89c7b..d7aeec03c57f 100644 > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > > } > > > > if (mm_pgtables_bytes(mm)) > > - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > > - mm_pgtables_bytes(mm)); > > + printk_once(KERN_ALERT "BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > > + mm_pgtables_bytes(mm)); > > You can be the first user of pr_alert_once(). Don't miss a chance! ;) I didn't expect that that one exists. ;) Will do. ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-11-27 7:34 ` Heiko Carstens 2018-11-27 8:05 ` Kirill A. Shutemov @ 2018-11-27 11:47 ` Guenter Roeck 2018-11-27 11:52 ` Heiko Carstens 2018-11-27 14:31 ` Martin Schwidefsky 2 siblings, 1 reply; 19+ messages in thread From: Guenter Roeck @ 2018-11-27 11:47 UTC (permalink / raw) To: Heiko Carstens, Kirill A. Shutemov Cc: Kirill A. Shutemov, Li Wang, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On 11/26/18 11:34 PM, Heiko Carstens wrote: > On Wed, Oct 31, 2018 at 01:36:23PM +0300, Kirill A. Shutemov wrote: >> On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote: >>> On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: >>>> Thanks for testing. Unfortunately Heiko reported another issue yesterday >>>> with the patch applied. This time the other way around: >>>> >>>> BUG: non-zero pgtables_bytes on freeing mm: -16384 >>>> >>>> I am trying to understand how this can happen. For now I would like to >>>> keep the patch on hold in case they need another change. >>> >>> FWIW, Kirill: is there a reason why this "BUG:" output is done with >>> pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? >>> >>> That would to get more information with DEBUG_VM and / or >>> panic_on_warn=1 set. At least for automated testing it would be nice >>> to have such triggers. >> >> Stack trace is not helpful there. It will always show the exit path which >> is useless. > > So, even with the updated version of these patches I can flood dmesg > and the console with > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > messages with this complex reproducer on s390: > > echo "void main(void) {}" | gcc -m31 -xc -o compat - && ./compat > > Besides that this needs to be fixed, I'd really like to see this > changed to either a printk_once() or a WARN_ON_ONCE() within > check_mm() so that an arbitrary user cannot flood the console. > > E.g. something like the below. If there aren't any objections, I will > provide a proper patch with changelog, etc. > > diff --git a/kernel/fork.c b/kernel/fork.c > index 07cddff89c7b..d7aeec03c57f 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > } > > if (mm_pgtables_bytes(mm)) > - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > - mm_pgtables_bytes(mm)); > + printk_once(KERN_ALERT "BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > + mm_pgtables_bytes(mm)); > pr_alert_once ? Guenter > #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS > VM_BUG_ON_MM(mm->pmd_huge_pte, mm); > > ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-11-27 11:47 ` Guenter Roeck @ 2018-11-27 11:52 ` Heiko Carstens 0 siblings, 0 replies; 19+ messages in thread From: Heiko Carstens @ 2018-11-27 11:52 UTC (permalink / raw) To: Guenter Roeck Cc: Kirill A. Shutemov, Kirill A. Shutemov, Li Wang, Janosch Frank, linux-kernel, Linux-MM, Martin Schwidefsky On Tue, Nov 27, 2018 at 03:47:13AM -0800, Guenter Roeck wrote: > >E.g. something like the below. If there aren't any objections, I will > >provide a proper patch with changelog, etc. > > > >diff --git a/kernel/fork.c b/kernel/fork.c > >index 07cddff89c7b..d7aeec03c57f 100644 > >--- a/kernel/fork.c > >+++ b/kernel/fork.c > >@@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > > } > > if (mm_pgtables_bytes(mm)) > >- pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > >- mm_pgtables_bytes(mm)); > >+ printk_once(KERN_ALERT "BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > >+ mm_pgtables_bytes(mm)); > > pr_alert_once ? Already changed and posted: https://lore.kernel.org/lkml/20181127083603.39041-1-heiko.carstens@de.ibm.com/ ^ permalink raw reply [flat|nested] 19+ messages in thread
* Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes 2018-11-27 7:34 ` Heiko Carstens 2018-11-27 8:05 ` Kirill A. Shutemov 2018-11-27 11:47 ` Guenter Roeck @ 2018-11-27 14:31 ` Martin Schwidefsky 2 siblings, 0 replies; 19+ messages in thread From: Martin Schwidefsky @ 2018-11-27 14:31 UTC (permalink / raw) To: Heiko Carstens Cc: Kirill A. Shutemov, Kirill A. Shutemov, Li Wang, Guenter Roeck, Janosch Frank, linux-kernel, Linux-MM On Tue, 27 Nov 2018 08:34:12 +0100 Heiko Carstens <heiko.carstens@de.ibm.com> wrote: > On Wed, Oct 31, 2018 at 01:36:23PM +0300, Kirill A. Shutemov wrote: > > On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote: > > > On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote: > > > > Thanks for testing. Unfortunately Heiko reported another issue yesterday > > > > with the patch applied. This time the other way around: > > > > > > > > BUG: non-zero pgtables_bytes on freeing mm: -16384 > > > > > > > > I am trying to understand how this can happen. For now I would like to > > > > keep the patch on hold in case they need another change. > > > > > > FWIW, Kirill: is there a reason why this "BUG:" output is done with > > > pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants? > > > > > > That would to get more information with DEBUG_VM and / or > > > panic_on_warn=1 set. At least for automated testing it would be nice > > > to have such triggers. > > > > Stack trace is not helpful there. It will always show the exit path which > > is useless. > > So, even with the updated version of these patches I can flood dmesg > and the console with > > BUG: non-zero pgtables_bytes on freeing mm: 16384 > > messages with this complex reproducer on s390: > > echo "void main(void) {}" | gcc -m31 -xc -o compat - && ./compat Forgot a hunk in the fix.. I claim not enough coffee :-/ Patch is queued and I will send a please pull by the end of the week. -- From c0499f2aa853939984ecaf0d393012486e56c7ce Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky <schwidefsky@de.ibm.com> Date: Tue, 27 Nov 2018 14:04:04 +0100 Subject: [PATCH] s390/mm: correct pgtable_bytes on page table downgrade The downgrade of a page table from 3 levels to 2 levels for a 31-bit compat process removes a pmd table which has to be counted against pgtable_bytes. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> --- arch/s390/mm/pgalloc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 814f26520aa2..6791562779ee 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -131,6 +131,7 @@ void crst_table_downgrade(struct mm_struct *mm) } pgd = mm->pgd; + mm_dec_nr_pmds(mm); mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN); mm->context.asce_limit = _REGION3_SIZE; mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | -- 2.16.4 -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. ^ permalink raw reply related [flat|nested] 19+ messages in thread
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Thread overview: 19+ messages (download: mbox.gz / follow: Atom feed)
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2018-10-15 16:42 [RFC][PATCH 0/3] pgtable bytes mis-accounting v2 Martin Schwidefsky
2018-10-15 16:42 ` [PATCH 1/3] mm: introduce mm_[p4d|pud|pmd]_folded Martin Schwidefsky
2018-10-31 9:02 ` Kirill A. Shutemov
2018-10-31 9:35 ` Martin Schwidefsky
2018-10-31 9:48 ` Kirill A. Shutemov
2018-10-15 16:42 ` [PATCH 2/3] mm: add mm_pxd_folded checks to pgtable_bytes accounting functions Martin Schwidefsky
2018-10-31 9:04 ` Kirill A. Shutemov
2018-10-15 16:42 ` [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes Martin Schwidefsky
[not found] ` <CAEemH2cHNFsiDqPF32K6TNn-XoXCRT0wP4ccAeah4bKHt=FKFA@mail.gmail.com>
2018-10-31 6:31 ` Martin Schwidefsky
[not found] ` <CAEemH2f2gW22PJYpVrh7p5zJyHOVRfVawJWD+kN3+8LmApePbw@mail.gmail.com>
2018-10-31 6:46 ` Martin Schwidefsky
2018-10-31 9:39 ` Martin Schwidefsky
2018-10-31 10:09 ` Heiko Carstens
2018-10-31 10:36 ` Kirill A. Shutemov
2018-11-27 7:34 ` Heiko Carstens
2018-11-27 8:05 ` Kirill A. Shutemov
2018-11-27 8:13 ` Heiko Carstens
2018-11-27 11:47 ` Guenter Roeck
2018-11-27 11:52 ` Heiko Carstens
2018-11-27 14:31 ` Martin Schwidefsky
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