| Message ID | 20191010135825.28153-1-richardw.yang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] mm/rmap.c: don't reuse anon_vma if we just want a copy | expand |
On 10/10/2019 16.58, Wei Yang wrote: > Before commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma > hierarchy"), anon_vma_clone() doesn't change dst->anon_vma. While after > this commit, anon_vma_clone() will try to reuse an exist one on forking. > > But this commit go a little bit further for the case not forking. > anon_vma_clone() is called from __vma_split(), __split_vma(), copy_vma() > and anon_vma_fork(). For the first three places, the purpose here is get > a copy of src and we don't expect to touch dst->anon_vma even it is > NULL. While after that commit, it is possible to reuse an anon_vma when > dst->anon_vma is NULL. This is not we intend to have. In all these cases dst->anon_vma is a copy of src->anon_vma except anon_vma_fork where dst_>anon_vma explicitly set to NULL before call. So reuse == true iff (!dst->anon_vma && src->anon_vma) > > This patch stop reuse anon_vma for non-fork cases. > > Fix commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma > hierarchy") > > Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> > --- > include/linux/rmap.h | 3 ++- > mm/mmap.c | 6 +++--- > mm/rmap.c | 7 ++++--- > 3 files changed, 9 insertions(+), 7 deletions(-) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 988d176472df..963e6ab09b9b 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -142,7 +142,8 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) > void anon_vma_init(void); /* create anon_vma_cachep */ > int __anon_vma_prepare(struct vm_area_struct *); > void unlink_anon_vmas(struct vm_area_struct *); > -int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); > +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, > + bool reuse); > int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); > > static inline int anon_vma_prepare(struct vm_area_struct *vma) > diff --git a/mm/mmap.c b/mm/mmap.c > index 93f221785956..21e94f8ac4c7 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -791,7 +791,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, > int error; > > importer->anon_vma = exporter->anon_vma; > - error = anon_vma_clone(importer, exporter); > + error = anon_vma_clone(importer, exporter, false); > if (error) > return error; > } > @@ -2666,7 +2666,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, > if (err) > goto out_free_vma; > > - err = anon_vma_clone(new, vma); > + err = anon_vma_clone(new, vma, false); > if (err) > goto out_free_mpol; > > @@ -3247,7 +3247,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, > new_vma->vm_pgoff = pgoff; > if (vma_dup_policy(vma, new_vma)) > goto out_free_vma; > - if (anon_vma_clone(new_vma, vma)) > + if (anon_vma_clone(new_vma, vma, false)) > goto out_free_mempol; > if (new_vma->vm_file) > get_file(new_vma->vm_file); > diff --git a/mm/rmap.c b/mm/rmap.c > index d9a23bb773bf..f729e4013613 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -258,7 +258,8 @@ static inline void unlock_anon_vma_root(struct anon_vma *root) > * good chance of avoiding scanning the whole hierarchy when it searches where > * page is mapped. > */ > -int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) > +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, > + bool reuse) > { > struct anon_vma_chain *avc, *pavc; > struct anon_vma *root = NULL; > @@ -286,7 +287,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) > * will always reuse it. Root anon_vma is never reused: > * it has self-parent reference and at least one child. > */ > - if (!dst->anon_vma && anon_vma != src->anon_vma && > + if (reuse && !dst->anon_vma && anon_vma != src->anon_vma && > anon_vma->degree < 2) > dst->anon_vma = anon_vma; > } > @@ -329,7 +330,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) > * First, attach the new VMA to the parent VMA's anon_vmas, > * so rmap can find non-COWed pages in child processes. > */ > - error = anon_vma_clone(vma, pvma); > + error = anon_vma_clone(vma, pvma, true); > if (error) > return error; > >
On Thu, Oct 10, 2019 at 06:29:32PM +0300, Konstantin Khlebnikov wrote: >On 10/10/2019 16.58, Wei Yang wrote: >> Before commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy"), anon_vma_clone() doesn't change dst->anon_vma. While after >> this commit, anon_vma_clone() will try to reuse an exist one on forking. >> >> But this commit go a little bit further for the case not forking. >> anon_vma_clone() is called from __vma_split(), __split_vma(), copy_vma() >> and anon_vma_fork(). For the first three places, the purpose here is get >> a copy of src and we don't expect to touch dst->anon_vma even it is >> NULL. While after that commit, it is possible to reuse an anon_vma when >> dst->anon_vma is NULL. This is not we intend to have. > >In all these cases dst->anon_vma is a copy of src->anon_vma except >anon_vma_fork where dst_>anon_vma explicitly set to NULL before call. > >So reuse == true iff (!dst->anon_vma && src->anon_vma) > What if src->anon_vma is NULL? >> >> This patch stop reuse anon_vma for non-fork cases. >> >> Fix commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy") >> >> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> >> --- >> include/linux/rmap.h | 3 ++- >> mm/mmap.c | 6 +++--- >> mm/rmap.c | 7 ++++--- >> 3 files changed, 9 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 988d176472df..963e6ab09b9b 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -142,7 +142,8 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) >> void anon_vma_init(void); /* create anon_vma_cachep */ >> int __anon_vma_prepare(struct vm_area_struct *); >> void unlink_anon_vmas(struct vm_area_struct *); >> -int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse); >> int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); >> static inline int anon_vma_prepare(struct vm_area_struct *vma) >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 93f221785956..21e94f8ac4c7 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -791,7 +791,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, >> int error; >> importer->anon_vma = exporter->anon_vma; >> - error = anon_vma_clone(importer, exporter); >> + error = anon_vma_clone(importer, exporter, false); >> if (error) >> return error; >> } >> @@ -2666,7 +2666,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, >> if (err) >> goto out_free_vma; >> - err = anon_vma_clone(new, vma); >> + err = anon_vma_clone(new, vma, false); >> if (err) >> goto out_free_mpol; >> @@ -3247,7 +3247,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, >> new_vma->vm_pgoff = pgoff; >> if (vma_dup_policy(vma, new_vma)) >> goto out_free_vma; >> - if (anon_vma_clone(new_vma, vma)) >> + if (anon_vma_clone(new_vma, vma, false)) >> goto out_free_mempol; >> if (new_vma->vm_file) >> get_file(new_vma->vm_file); >> diff --git a/mm/rmap.c b/mm/rmap.c >> index d9a23bb773bf..f729e4013613 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -258,7 +258,8 @@ static inline void unlock_anon_vma_root(struct anon_vma *root) >> * good chance of avoiding scanning the whole hierarchy when it searches where >> * page is mapped. >> */ >> -int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse) >> { >> struct anon_vma_chain *avc, *pavc; >> struct anon_vma *root = NULL; >> @@ -286,7 +287,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> * will always reuse it. Root anon_vma is never reused: >> * it has self-parent reference and at least one child. >> */ >> - if (!dst->anon_vma && anon_vma != src->anon_vma && >> + if (reuse && !dst->anon_vma && anon_vma != src->anon_vma && >> anon_vma->degree < 2) >> dst->anon_vma = anon_vma; >> } >> @@ -329,7 +330,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) >> * First, attach the new VMA to the parent VMA's anon_vmas, >> * so rmap can find non-COWed pages in child processes. >> */ >> - error = anon_vma_clone(vma, pvma); >> + error = anon_vma_clone(vma, pvma, true); >> if (error) >> return error; >>
On Thu, Oct 10, 2019 at 06:29:32PM +0300, Konstantin Khlebnikov wrote: >On 10/10/2019 16.58, Wei Yang wrote: >> Before commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy"), anon_vma_clone() doesn't change dst->anon_vma. While after >> this commit, anon_vma_clone() will try to reuse an exist one on forking. >> >> But this commit go a little bit further for the case not forking. >> anon_vma_clone() is called from __vma_split(), __split_vma(), copy_vma() >> and anon_vma_fork(). For the first three places, the purpose here is get >> a copy of src and we don't expect to touch dst->anon_vma even it is >> NULL. While after that commit, it is possible to reuse an anon_vma when >> dst->anon_vma is NULL. This is not we intend to have. > >In all these cases dst->anon_vma is a copy of src->anon_vma except >anon_vma_fork where dst_>anon_vma explicitly set to NULL before call. > >So reuse == true iff (!dst->anon_vma && src->anon_vma) > Ok, I think you are right. Thanks >> >> This patch stop reuse anon_vma for non-fork cases. >> >> Fix commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma >> hierarchy") >> >> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> >> --- >> include/linux/rmap.h | 3 ++- >> mm/mmap.c | 6 +++--- >> mm/rmap.c | 7 ++++--- >> 3 files changed, 9 insertions(+), 7 deletions(-) >> >> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >> index 988d176472df..963e6ab09b9b 100644 >> --- a/include/linux/rmap.h >> +++ b/include/linux/rmap.h >> @@ -142,7 +142,8 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) >> void anon_vma_init(void); /* create anon_vma_cachep */ >> int __anon_vma_prepare(struct vm_area_struct *); >> void unlink_anon_vmas(struct vm_area_struct *); >> -int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse); >> int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); >> static inline int anon_vma_prepare(struct vm_area_struct *vma) >> diff --git a/mm/mmap.c b/mm/mmap.c >> index 93f221785956..21e94f8ac4c7 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -791,7 +791,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, >> int error; >> importer->anon_vma = exporter->anon_vma; >> - error = anon_vma_clone(importer, exporter); >> + error = anon_vma_clone(importer, exporter, false); >> if (error) >> return error; >> } >> @@ -2666,7 +2666,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, >> if (err) >> goto out_free_vma; >> - err = anon_vma_clone(new, vma); >> + err = anon_vma_clone(new, vma, false); >> if (err) >> goto out_free_mpol; >> @@ -3247,7 +3247,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, >> new_vma->vm_pgoff = pgoff; >> if (vma_dup_policy(vma, new_vma)) >> goto out_free_vma; >> - if (anon_vma_clone(new_vma, vma)) >> + if (anon_vma_clone(new_vma, vma, false)) >> goto out_free_mempol; >> if (new_vma->vm_file) >> get_file(new_vma->vm_file); >> diff --git a/mm/rmap.c b/mm/rmap.c >> index d9a23bb773bf..f729e4013613 100644 >> --- a/mm/rmap.c >> +++ b/mm/rmap.c >> @@ -258,7 +258,8 @@ static inline void unlock_anon_vma_root(struct anon_vma *root) >> * good chance of avoiding scanning the whole hierarchy when it searches where >> * page is mapped. >> */ >> -int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, >> + bool reuse) >> { >> struct anon_vma_chain *avc, *pavc; >> struct anon_vma *root = NULL; >> @@ -286,7 +287,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) >> * will always reuse it. Root anon_vma is never reused: >> * it has self-parent reference and at least one child. >> */ >> - if (!dst->anon_vma && anon_vma != src->anon_vma && >> + if (reuse && !dst->anon_vma && anon_vma != src->anon_vma && >> anon_vma->degree < 2) >> dst->anon_vma = anon_vma; >> } >> @@ -329,7 +330,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) >> * First, attach the new VMA to the parent VMA's anon_vmas, >> * so rmap can find non-COWed pages in child processes. >> */ >> - error = anon_vma_clone(vma, pvma); >> + error = anon_vma_clone(vma, pvma, true); >> if (error) >> return error; >>
diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 988d176472df..963e6ab09b9b 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -142,7 +142,8 @@ static inline void anon_vma_unlock_read(struct anon_vma *anon_vma) void anon_vma_init(void); /* create anon_vma_cachep */ int __anon_vma_prepare(struct vm_area_struct *); void unlink_anon_vmas(struct vm_area_struct *); -int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *); +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, + bool reuse); int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *); static inline int anon_vma_prepare(struct vm_area_struct *vma) diff --git a/mm/mmap.c b/mm/mmap.c index 93f221785956..21e94f8ac4c7 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -791,7 +791,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, int error; importer->anon_vma = exporter->anon_vma; - error = anon_vma_clone(importer, exporter); + error = anon_vma_clone(importer, exporter, false); if (error) return error; } @@ -2666,7 +2666,7 @@ int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma, if (err) goto out_free_vma; - err = anon_vma_clone(new, vma); + err = anon_vma_clone(new, vma, false); if (err) goto out_free_mpol; @@ -3247,7 +3247,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, new_vma->vm_pgoff = pgoff; if (vma_dup_policy(vma, new_vma)) goto out_free_vma; - if (anon_vma_clone(new_vma, vma)) + if (anon_vma_clone(new_vma, vma, false)) goto out_free_mempol; if (new_vma->vm_file) get_file(new_vma->vm_file); diff --git a/mm/rmap.c b/mm/rmap.c index d9a23bb773bf..f729e4013613 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -258,7 +258,8 @@ static inline void unlock_anon_vma_root(struct anon_vma *root) * good chance of avoiding scanning the whole hierarchy when it searches where * page is mapped. */ -int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, + bool reuse) { struct anon_vma_chain *avc, *pavc; struct anon_vma *root = NULL; @@ -286,7 +287,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) * will always reuse it. Root anon_vma is never reused: * it has self-parent reference and at least one child. */ - if (!dst->anon_vma && anon_vma != src->anon_vma && + if (reuse && !dst->anon_vma && anon_vma != src->anon_vma && anon_vma->degree < 2) dst->anon_vma = anon_vma; } @@ -329,7 +330,7 @@ int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) * First, attach the new VMA to the parent VMA's anon_vmas, * so rmap can find non-COWed pages in child processes. */ - error = anon_vma_clone(vma, pvma); + error = anon_vma_clone(vma, pvma, true); if (error) return error;
Before commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy"), anon_vma_clone() doesn't change dst->anon_vma. While after this commit, anon_vma_clone() will try to reuse an exist one on forking. But this commit go a little bit further for the case not forking. anon_vma_clone() is called from __vma_split(), __split_vma(), copy_vma() and anon_vma_fork(). For the first three places, the purpose here is get a copy of src and we don't expect to touch dst->anon_vma even it is NULL. While after that commit, it is possible to reuse an anon_vma when dst->anon_vma is NULL. This is not we intend to have. This patch stop reuse anon_vma for non-fork cases. Fix commit 7a3ef208e662 ("mm: prevent endless growth of anon_vma hierarchy") Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> --- include/linux/rmap.h | 3 ++- mm/mmap.c | 6 +++--- mm/rmap.c | 7 ++++--- 3 files changed, 9 insertions(+), 7 deletions(-)