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SubjectRe: PING: [PATCH v2] perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled
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Ping again, sorry for the noise.

On Thu, February 17, 2022 12:54 AM, Zhipeng Xie wrote:
>
> Hi, Peter
>
> Could you please review the V2 version?
>
> On Wed, February 9, 2022 10:54 PM, Zhipeng Xie wrote:
> > This problem can be reproduced with CONFIG_PERF_USE_VMALLOC enabled
> > on both
> > x86_64 and aarch64 arch when using sysdig -B(using ebpf)[1].
> > sysdig -B works fine after rebuilding the kernel with
> > CONFIG_PERF_USE_VMALLOC
> > disabled.
> >
> > I tracked it down to the if condition event->rb->nr_pages != nr_pages in
> > perf_mmap is true when CONFIG_PERF_USE_VMALLOC is enabled where
> > event->rb->nr_pages = 1 and nr_pages = 2048 resulting perf_mmap to return
> > -EINVAL.This is because when CONFIG_PERF_USE_VMALLOC is enabled,
> > rb->nr_pages
> > is always equal to 1.
> >
> > Arch with CONFIG_PERF_USE_VMALLOC enabled by default:
> > arc/arm/csky/mips/sh/sparc/xtensa
> > Arch with CONFIG_PERF_USE_VMALLOC disabled by default:
> > x86_64/aarch64/...
> >
> > Fix this problem by using data_page_nr.
> >
> > [1] https://github.com/draios/sysdig
> >
> > Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
> > ---
> > kernel/events/core.c | 2 +-
> > kernel/events/internal.h | 5 +++++
> > kernel/events/ring_buffer.c | 5 -----
> > 3 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > index 57c7197838db..370292effd32 100644
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -6352,7 +6352,7 @@ static int perf_mmap(struct file *file, struct
> > vm_area_struct *vma)
> > again:
> > mutex_lock(&event->mmap_mutex);
> > if (event->rb) {
> > - if (event->rb->nr_pages != nr_pages) {
> > + if (data_page_nr(event->rb) != nr_pages) {
> > ret = -EINVAL;
> > goto unlock;
> > }
> > diff --git a/kernel/events/internal.h b/kernel/events/internal.h
> > index 082832738c8f..5816c0719dbf 100644
> > --- a/kernel/events/internal.h
> > +++ b/kernel/events/internal.h
> > @@ -116,6 +116,11 @@ static inline int page_order(struct perf_buffer *rb)
> > }
> > #endif
> >
> > +static int data_page_nr(struct perf_buffer *rb)
> > +{
> > + return rb->nr_pages << page_order(rb);
> > +}
> > +
> > static inline unsigned long perf_data_size(struct perf_buffer *rb)
> > {
> > return rb->nr_pages << (PAGE_SHIFT + page_order(rb));
> > diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> > index 52868716ec35..fb35b926024c 100644
> > --- a/kernel/events/ring_buffer.c
> > +++ b/kernel/events/ring_buffer.c
> > @@ -859,11 +859,6 @@ void rb_free(struct perf_buffer *rb)
> > }
> >
> > #else
> > -static int data_page_nr(struct perf_buffer *rb)
> > -{
> > - return rb->nr_pages << page_order(rb);
> > -}
> > -
> > static struct page *
> > __perf_mmap_to_page(struct perf_buffer *rb, unsigned long pgoff)
> > {
> > --
> > 2.18.1
>
> Best Regards,
> Zhipeng Xie

Best Regards,
Zhipeng Xie

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