Introduce pin_user_pages_locked(), which is nearly identical to
get_user_pages_locked() except that it sets FOLL_PIN and rejects
FOLL_GET.
Signed-off-by: John Hubbard <[email protected]>
---
include/linux/mm.h | 2 ++
mm/gup.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 32 insertions(+)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 98be7289d7e9..d16951087c93 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1700,6 +1700,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
struct vm_area_struct **vmas);
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages, int *locked);
+long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
+ unsigned int gup_flags, struct page **pages, int *locked);
long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
struct page **pages, unsigned int gup_flags);
long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
diff --git a/mm/gup.c b/mm/gup.c
index 2f0a0b497c23..17418a949067 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2992,3 +2992,33 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages_unlocked);
+
+/*
+ * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
+ * Behavior is the same, except that this one sets FOLL_PIN and rejects
+ * FOLL_GET.
+ */
+long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
+ unsigned int gup_flags, struct page **pages,
+ int *locked)
+{
+ /*
+ * FIXME: Current FOLL_LONGTERM behavior is incompatible with
+ * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
+ * vmas. As there are no users of this flag in this call we simply
+ * disallow this option for now.
+ */
+ if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
+ return -EINVAL;
+
+ /* FOLL_GET and FOLL_PIN are mutually exclusive. */
+ if (WARN_ON_ONCE(gup_flags & FOLL_GET))
+ return -EINVAL;
+
+ gup_flags |= FOLL_PIN;
+ return __get_user_pages_locked(current, current->mm, start, nr_pages,
+ pages, NULL, locked,
+ gup_flags | FOLL_TOUCH);
+}
+EXPORT_SYMBOL(pin_user_pages_locked);
+
--
2.26.2
On 28.05.20 00:32, John Hubbard wrote:
> Introduce pin_user_pages_locked(), which is nearly identical to
> get_user_pages_locked() except that it sets FOLL_PIN and rejects
> FOLL_GET.
>
> Signed-off-by: John Hubbard <[email protected]>
> ---
> include/linux/mm.h | 2 ++
> mm/gup.c | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 98be7289d7e9..d16951087c93 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1700,6 +1700,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
> struct vm_area_struct **vmas);
> long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
> unsigned int gup_flags, struct page **pages, int *locked);
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages, int *locked);
> long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> struct page **pages, unsigned int gup_flags);
> long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> diff --git a/mm/gup.c b/mm/gup.c
> index 2f0a0b497c23..17418a949067 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2992,3 +2992,33 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
> }
> EXPORT_SYMBOL(pin_user_pages_unlocked);
> +
> +/*
> + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
> + * Behavior is the same, except that this one sets FOLL_PIN and rejects
> + * FOLL_GET.
> + */
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages,
> + int *locked)
> +{
> + /*
> + * FIXME: Current FOLL_LONGTERM behavior is incompatible with
> + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
> + * vmas. As there are no users of this flag in this call we simply
> + * disallow this option for now.
> + */
> + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
> + return -EINVAL;
> +
> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */
> + if (WARN_ON_ONCE(gup_flags & FOLL_GET))
> + return -EINVAL;
> +
> + gup_flags |= FOLL_PIN;
> + return __get_user_pages_locked(current, current->mm, start, nr_pages,
> + pages, NULL, locked,
> + gup_flags | FOLL_TOUCH);
> +}
> +EXPORT_SYMBOL(pin_user_pages_locked);
> +
>
LGTM
Reviewed-by: David Hildenbrand <[email protected]>
--
Thanks,
David / dhildenb
On Thu, May 28, 2020 at 4:02 AM John Hubbard <[email protected]> wrote:
>
> Introduce pin_user_pages_locked(), which is nearly identical to
> get_user_pages_locked() except that it sets FOLL_PIN and rejects
> FOLL_GET.
>
> Signed-off-by: John Hubbard <[email protected]>
> ---
> include/linux/mm.h | 2 ++
> mm/gup.c | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 98be7289d7e9..d16951087c93 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1700,6 +1700,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
> struct vm_area_struct **vmas);
> long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
> unsigned int gup_flags, struct page **pages, int *locked);
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages, int *locked);
> long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> struct page **pages, unsigned int gup_flags);
> long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> diff --git a/mm/gup.c b/mm/gup.c
> index 2f0a0b497c23..17418a949067 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2992,3 +2992,33 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
> }
> EXPORT_SYMBOL(pin_user_pages_unlocked);
> +
> +/*
> + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
> + * Behavior is the same, except that this one sets FOLL_PIN and rejects
> + * FOLL_GET.
> + */
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages,
> + int *locked)
> +{
> + /*
> + * FIXME: Current FOLL_LONGTERM behavior is incompatible with
> + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
> + * vmas. As there are no users of this flag in this call we simply
> + * disallow this option for now.
> + */
> + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
> + return -EINVAL;
> +
> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */
> + if (WARN_ON_ONCE(gup_flags & FOLL_GET))
> + return -EINVAL;
> +
> + gup_flags |= FOLL_PIN;
Right now get_user_pages_locked() doesn't have similar check for FOLL_PIN
and also not setting FOLL_GET internally irrespective of gup_flags
passed by user.
Do we need to add the same in get_user_pages_locked() ?
> + return __get_user_pages_locked(current, current->mm, start, nr_pages,
> + pages, NULL, locked,
> + gup_flags | FOLL_TOUCH);
> +}
> +EXPORT_SYMBOL(pin_user_pages_locked);
> +
> --
> 2.26.2
>
>
On Sun, May 31, 2020 at 12:34 PM Souptick Joarder <[email protected]> wrote:
>
> On Thu, May 28, 2020 at 4:02 AM John Hubbard <[email protected]> wrote:
> >
> > Introduce pin_user_pages_locked(), which is nearly identical to
> > get_user_pages_locked() except that it sets FOLL_PIN and rejects
> > FOLL_GET.
Forget to ask, is it fine to add this new pin_user_pages_locked() in
Documentation/core-api/pin_user_pages.rst ?
> >
> > Signed-off-by: John Hubbard <[email protected]>
> > ---
> > include/linux/mm.h | 2 ++
> > mm/gup.c | 30 ++++++++++++++++++++++++++++++
> > 2 files changed, 32 insertions(+)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 98be7289d7e9..d16951087c93 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1700,6 +1700,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
> > struct vm_area_struct **vmas);
> > long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
> > unsigned int gup_flags, struct page **pages, int *locked);
> > +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> > + unsigned int gup_flags, struct page **pages, int *locked);
> > long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> > struct page **pages, unsigned int gup_flags);
> > long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> > diff --git a/mm/gup.c b/mm/gup.c
> > index 2f0a0b497c23..17418a949067 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -2992,3 +2992,33 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> > return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
> > }
> > EXPORT_SYMBOL(pin_user_pages_unlocked);
> > +
> > +/*
> > + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
> > + * Behavior is the same, except that this one sets FOLL_PIN and rejects
> > + * FOLL_GET.
> > + */
> > +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> > + unsigned int gup_flags, struct page **pages,
> > + int *locked)
> > +{
> > + /*
> > + * FIXME: Current FOLL_LONGTERM behavior is incompatible with
> > + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
> > + * vmas. As there are no users of this flag in this call we simply
> > + * disallow this option for now.
> > + */
> > + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
> > + return -EINVAL;
> > +
> > + /* FOLL_GET and FOLL_PIN are mutually exclusive. */
> > + if (WARN_ON_ONCE(gup_flags & FOLL_GET))
> > + return -EINVAL;
> > +
> > + gup_flags |= FOLL_PIN;
>
> Right now get_user_pages_locked() doesn't have similar check for FOLL_PIN
> and also not setting FOLL_GET internally irrespective of gup_flags
> passed by user.
> Do we need to add the same in get_user_pages_locked() ?
>
> > + return __get_user_pages_locked(current, current->mm, start, nr_pages,
> > + pages, NULL, locked,
> > + gup_flags | FOLL_TOUCH);
> > +}
> > +EXPORT_SYMBOL(pin_user_pages_locked);
> > +
> > --
> > 2.26.2
> >
> >
Acked-by: Pankaj Gupta <[email protected]>
On Thu, 28 May 2020 at 00:32, John Hubbard <[email protected]> wrote:
>
> Introduce pin_user_pages_locked(), which is nearly identical to
> get_user_pages_locked() except that it sets FOLL_PIN and rejects
> FOLL_GET.
>
> Signed-off-by: John Hubbard <[email protected]>
> ---
> include/linux/mm.h | 2 ++
> mm/gup.c | 30 ++++++++++++++++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 98be7289d7e9..d16951087c93 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1700,6 +1700,8 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
> struct vm_area_struct **vmas);
> long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
> unsigned int gup_flags, struct page **pages, int *locked);
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages, int *locked);
> long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> struct page **pages, unsigned int gup_flags);
> long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> diff --git a/mm/gup.c b/mm/gup.c
> index 2f0a0b497c23..17418a949067 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2992,3 +2992,33 @@ long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
> return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
> }
> EXPORT_SYMBOL(pin_user_pages_unlocked);
> +
> +/*
> + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
> + * Behavior is the same, except that this one sets FOLL_PIN and rejects
> + * FOLL_GET.
> + */
> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
> + unsigned int gup_flags, struct page **pages,
> + int *locked)
> +{
> + /*
> + * FIXME: Current FOLL_LONGTERM behavior is incompatible with
> + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
> + * vmas. As there are no users of this flag in this call we simply
> + * disallow this option for now.
> + */
> + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
> + return -EINVAL;
> +
> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */
> + if (WARN_ON_ONCE(gup_flags & FOLL_GET))
> + return -EINVAL;
> +
> + gup_flags |= FOLL_PIN;
> + return __get_user_pages_locked(current, current->mm, start, nr_pages,
> + pages, NULL, locked,
> + gup_flags | FOLL_TOUCH);
> +}
> +EXPORT_SYMBOL(pin_user_pages_locked);
> +
> --
> 2.26.2
>
>
On 2020-05-31 00:04, Souptick Joarder wrote:
...
>> +/*
>> + * pin_user_pages_locked() is the FOLL_PIN variant of get_user_pages_locked().
>> + * Behavior is the same, except that this one sets FOLL_PIN and rejects
>> + * FOLL_GET.
>> + */
>> +long pin_user_pages_locked(unsigned long start, unsigned long nr_pages,
>> + unsigned int gup_flags, struct page **pages,
>> + int *locked)
>> +{
>> + /*
>> + * FIXME: Current FOLL_LONGTERM behavior is incompatible with
>> + * FAULT_FLAG_ALLOW_RETRY because of the FS DAX check requirement on
>> + * vmas. As there are no users of this flag in this call we simply
>> + * disallow this option for now.
>> + */
>> + if (WARN_ON_ONCE(gup_flags & FOLL_LONGTERM))
>> + return -EINVAL;
>> +
>> + /* FOLL_GET and FOLL_PIN are mutually exclusive. */
>> + if (WARN_ON_ONCE(gup_flags & FOLL_GET))
>> + return -EINVAL;
>> +
>> + gup_flags |= FOLL_PIN;
>
> Right now get_user_pages_locked() doesn't have similar check for FOLL_PIN
Yes, that should be added...
> and also not setting FOLL_GET internally irrespective of gup_flags
> passed by user.
> Do we need to add the same in get_user_pages_locked() ?
...and no, that should not.
Yes, it's prudent to assert that FOLL_PIN is *not* set, at all the
get_user_pages*() API calls, thanks for spotting that. I'll add that to
this patch and send out a v2.
The same check should also be added to get_user_pages_unlocked(). I'll send
out a correction (I think just a v3 of that patchset) to add that.
The setting of FOLL_GET, on the other hand, is something best left as-is
so far. Some call sites set FOLL_GET, some want it *not* set, and some
expect that FOLL_GET is implied, and at the moment, the delicate balance is
correct. :)
thanks,
--
John Hubbard
NVIDIA
On 2020-05-31 00:13, Souptick Joarder wrote:
> On Sun, May 31, 2020 at 12:34 PM Souptick Joarder <[email protected]> wrote:
>>
>> On Thu, May 28, 2020 at 4:02 AM John Hubbard <[email protected]> wrote:
>>>
>>> Introduce pin_user_pages_locked(), which is nearly identical to
>>> get_user_pages_locked() except that it sets FOLL_PIN and rejects
>>> FOLL_GET.
>
> Forget to ask, is it fine to add this new pin_user_pages_locked() in
> Documentation/core-api/pin_user_pages.rst ?
>
I wasn't planning on maintaining a rigorous list of all of the pin_user_page*()
API calls, in pin_user_pages.rst. Each call is documented in gup.c, for that.
The .rst is there to help explain things at a slighly higher abstraction level.
thanks,
--
John Hubbard
NVIDIA