* [PATCH v2 0/3] Few bug fixes and Convert to pin_user_pages*()
@ 2020-07-06 18:16 Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 1/3] xen/privcmd: Corrected error handling path Souptick Joarder
` (2 more replies)
0 siblings, 3 replies; 14+ messages in thread
From: Souptick Joarder @ 2020-07-06 18:16 UTC (permalink / raw)
To: boris.ostrovsky, jgross, sstabellini
Cc: xen-devel, linux-kernel, Souptick Joarder, John Hubbard, Paul Durrant
This series contains few clean up, minor bug fixes and
Convert get_user_pages() to pin_user_pages().
I'm compile tested this, but unable to run-time test,
so any testing help is much appriciated.
v2:
Addressed few review comments and compile issue.
Patch[1/2] from v1 split into 2 in v2.
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Paul Durrant <xadimgnik@gmail.com>
Souptick Joarder (3):
xen/privcmd: Corrected error handling path
xen/privcmd: Mark pages as dirty
xen/privcmd: Convert get_user_pages*() to pin_user_pages*()
drivers/xen/privcmd.c | 32 ++++++++++++++------------------
1 file changed, 14 insertions(+), 18 deletions(-)
--
1.9.1
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v2 1/3] xen/privcmd: Corrected error handling path
2020-07-06 18:16 [PATCH v2 0/3] Few bug fixes and Convert to pin_user_pages*() Souptick Joarder
@ 2020-07-06 18:16 ` Souptick Joarder
2020-07-07 9:35 ` Jürgen Groß
2020-07-06 18:16 ` [PATCH v2 2/3] xen/privcmd: Mark pages as dirty Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*() Souptick Joarder
2 siblings, 1 reply; 14+ messages in thread
From: Souptick Joarder @ 2020-07-06 18:16 UTC (permalink / raw)
To: boris.ostrovsky, jgross, sstabellini
Cc: xen-devel, linux-kernel, Souptick Joarder, John Hubbard, Paul Durrant
Previously, if lock_pages() end up partially mapping pages, it used
to return -ERRNO due to which unlock_pages() have to go through
each pages[i] till *nr_pages* to validate them. This can be avoided
by passing correct number of partially mapped pages & -ERRNO separately,
while returning from lock_pages() due to error.
With this fix unlock_pages() doesn't need to validate pages[i] till
*nr_pages* for error scenario and few condition checks can be ignored.
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Paul Durrant <xadimgnik@gmail.com>
---
drivers/xen/privcmd.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index a250d11..33677ea 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
static int lock_pages(
struct privcmd_dm_op_buf kbufs[], unsigned int num,
- struct page *pages[], unsigned int nr_pages)
+ struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
{
unsigned int i;
+ int page_count = 0;
for (i = 0; i < num; i++) {
unsigned int requested;
- int pinned;
requested = DIV_ROUND_UP(
offset_in_page(kbufs[i].uptr) + kbufs[i].size,
@@ -594,14 +594,15 @@ static int lock_pages(
if (requested > nr_pages)
return -ENOSPC;
- pinned = get_user_pages_fast(
+ page_count = get_user_pages_fast(
(unsigned long) kbufs[i].uptr,
requested, FOLL_WRITE, pages);
- if (pinned < 0)
- return pinned;
+ if (page_count < 0)
+ return page_count;
- nr_pages -= pinned;
- pages += pinned;
+ *pinned += page_count;
+ nr_pages -= page_count;
+ pages += page_count;
}
return 0;
@@ -611,13 +612,8 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
{
unsigned int i;
- if (!pages)
- return;
-
- for (i = 0; i < nr_pages; i++) {
- if (pages[i])
- put_page(pages[i]);
- }
+ for (i = 0; i < nr_pages; i++)
+ put_page(pages[i]);
}
static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
@@ -630,6 +626,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
struct xen_dm_op_buf *xbufs = NULL;
unsigned int i;
long rc;
+ unsigned int pinned = 0;
if (copy_from_user(&kdata, udata, sizeof(kdata)))
return -EFAULT;
@@ -683,9 +680,11 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
goto out;
}
- rc = lock_pages(kbufs, kdata.num, pages, nr_pages);
- if (rc)
+ rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
+ if (rc < 0) {
+ nr_pages = pinned;
goto out;
+ }
for (i = 0; i < kdata.num; i++) {
set_xen_guest_handle(xbufs[i].h, kbufs[i].uptr);
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-06 18:16 [PATCH v2 0/3] Few bug fixes and Convert to pin_user_pages*() Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 1/3] xen/privcmd: Corrected error handling path Souptick Joarder
@ 2020-07-06 18:16 ` Souptick Joarder
2020-07-07 9:38 ` Jürgen Groß
2020-07-06 18:16 ` [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*() Souptick Joarder
2 siblings, 1 reply; 14+ messages in thread
From: Souptick Joarder @ 2020-07-06 18:16 UTC (permalink / raw)
To: boris.ostrovsky, jgross, sstabellini
Cc: xen-devel, linux-kernel, Souptick Joarder, John Hubbard, Paul Durrant
pages need to be marked as dirty before unpinned it in
unlock_pages() which was oversight. This is fixed now.
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Suggested-by: John Hubbard <jhubbard@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Paul Durrant <xadimgnik@gmail.com>
---
drivers/xen/privcmd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 33677ea..f6c1543 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
{
unsigned int i;
- for (i = 0; i < nr_pages; i++)
+ for (i = 0; i < nr_pages; i++) {
+ if (!PageDirty(pages[i]))
+ set_page_dirty_lock(pages[i]);
put_page(pages[i]);
+ }
}
static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*()
2020-07-06 18:16 [PATCH v2 0/3] Few bug fixes and Convert to pin_user_pages*() Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 1/3] xen/privcmd: Corrected error handling path Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 2/3] xen/privcmd: Mark pages as dirty Souptick Joarder
@ 2020-07-06 18:16 ` Souptick Joarder
2020-07-07 11:49 ` Jürgen Groß
2 siblings, 1 reply; 14+ messages in thread
From: Souptick Joarder @ 2020-07-06 18:16 UTC (permalink / raw)
To: boris.ostrovsky, jgross, sstabellini
Cc: xen-devel, linux-kernel, Souptick Joarder, John Hubbard, Paul Durrant
In 2019, we introduced pin_user_pages*() and now we are converting
get_user_pages*() to the new API as appropriate. [1] & [2] could
be referred for more information. This is case 5 as per document [1].
[1] Documentation/core-api/pin_user_pages.rst
[2] "Explicit pinning of user-space pages":
https://lwn.net/Articles/807108/
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Paul Durrant <xadimgnik@gmail.com>
---
drivers/xen/privcmd.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index f6c1543..5c5cd24 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -594,7 +594,7 @@ static int lock_pages(
if (requested > nr_pages)
return -ENOSPC;
- page_count = get_user_pages_fast(
+ page_count = pin_user_pages_fast(
(unsigned long) kbufs[i].uptr,
requested, FOLL_WRITE, pages);
if (page_count < 0)
@@ -610,13 +610,7 @@ static int lock_pages(
static void unlock_pages(struct page *pages[], unsigned int nr_pages)
{
- unsigned int i;
-
- for (i = 0; i < nr_pages; i++) {
- if (!PageDirty(pages[i]))
- set_page_dirty_lock(pages[i]);
- put_page(pages[i]);
- }
+ unpin_user_pages_dirty_lock(pages, nr_pages, true);
}
static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path
2020-07-06 18:16 ` [PATCH v2 1/3] xen/privcmd: Corrected error handling path Souptick Joarder
@ 2020-07-07 9:35 ` Jürgen Groß
2020-07-07 11:40 ` Souptick Joarder
0 siblings, 1 reply; 14+ messages in thread
From: Jürgen Groß @ 2020-07-07 9:35 UTC (permalink / raw)
To: Souptick Joarder, boris.ostrovsky, sstabellini
Cc: xen-devel, linux-kernel, John Hubbard, Paul Durrant
On 06.07.20 20:16, Souptick Joarder wrote:
> Previously, if lock_pages() end up partially mapping pages, it used
> to return -ERRNO due to which unlock_pages() have to go through
> each pages[i] till *nr_pages* to validate them. This can be avoided
> by passing correct number of partially mapped pages & -ERRNO separately,
> while returning from lock_pages() due to error.
>
> With this fix unlock_pages() doesn't need to validate pages[i] till
> *nr_pages* for error scenario and few condition checks can be ignored.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Paul Durrant <xadimgnik@gmail.com>
> ---
> drivers/xen/privcmd.c | 31 +++++++++++++++----------------
> 1 file changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index a250d11..33677ea 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
>
> static int lock_pages(
> struct privcmd_dm_op_buf kbufs[], unsigned int num,
> - struct page *pages[], unsigned int nr_pages)
> + struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
> {
> unsigned int i;
> + int page_count = 0;
Initial value shouldn't be needed, and ...
>
> for (i = 0; i < num; i++) {
> unsigned int requested;
> - int pinned;
... you could move the declaration here.
With that done you can add my
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-06 18:16 ` [PATCH v2 2/3] xen/privcmd: Mark pages as dirty Souptick Joarder
@ 2020-07-07 9:38 ` Jürgen Groß
2020-07-07 11:30 ` Souptick Joarder
0 siblings, 1 reply; 14+ messages in thread
From: Jürgen Groß @ 2020-07-07 9:38 UTC (permalink / raw)
To: Souptick Joarder, boris.ostrovsky, sstabellini
Cc: xen-devel, linux-kernel, John Hubbard, Paul Durrant
On 06.07.20 20:16, Souptick Joarder wrote:
> pages need to be marked as dirty before unpinned it in
> unlock_pages() which was oversight. This is fixed now.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Suggested-by: John Hubbard <jhubbard@nvidia.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Paul Durrant <xadimgnik@gmail.com>
> ---
> drivers/xen/privcmd.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 33677ea..f6c1543 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
> {
> unsigned int i;
>
> - for (i = 0; i < nr_pages; i++)
> + for (i = 0; i < nr_pages; i++) {
> + if (!PageDirty(pages[i]))
> + set_page_dirty_lock(pages[i]);
With put_page() directly following I think you should be able to use
set_page_dirty() instead, as there is obviously a reference to the page
existing.
> put_page(pages[i]);
> + }
> }
>
> static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
>
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-07 9:38 ` Jürgen Groß
@ 2020-07-07 11:30 ` Souptick Joarder
2020-07-07 11:43 ` Jürgen Groß
0 siblings, 1 reply; 14+ messages in thread
From: Souptick Joarder @ 2020-07-07 11:30 UTC (permalink / raw)
To: Jürgen Groß
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel,
John Hubbard, Paul Durrant
On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß <jgross@suse.com> wrote:
>
> On 06.07.20 20:16, Souptick Joarder wrote:
> > pages need to be marked as dirty before unpinned it in
> > unlock_pages() which was oversight. This is fixed now.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > Suggested-by: John Hubbard <jhubbard@nvidia.com>
> > Cc: John Hubbard <jhubbard@nvidia.com>
> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Cc: Paul Durrant <xadimgnik@gmail.com>
> > ---
> > drivers/xen/privcmd.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index 33677ea..f6c1543 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
> > {
> > unsigned int i;
> >
> > - for (i = 0; i < nr_pages; i++)
> > + for (i = 0; i < nr_pages; i++) {
> > + if (!PageDirty(pages[i]))
> > + set_page_dirty_lock(pages[i]);
>
> With put_page() directly following I think you should be able to use
> set_page_dirty() instead, as there is obviously a reference to the page
> existing.
Patch [3/3] will convert above codes to use unpin_user_pages_dirty_lock()
which internally do the same check. So I thought to keep linux-stable and
linux-next code in sync. John had a similar concern [1] and later agreed to keep
this check.
Shall I keep this check ? No ?
[1] https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/
>
> > put_page(pages[i]);
> > + }
> > }
> >
> > static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> >
>
> Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path
2020-07-07 9:35 ` Jürgen Groß
@ 2020-07-07 11:40 ` Souptick Joarder
2020-07-07 11:45 ` Jürgen Groß
0 siblings, 1 reply; 14+ messages in thread
From: Souptick Joarder @ 2020-07-07 11:40 UTC (permalink / raw)
To: Jürgen Groß
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel,
John Hubbard, Paul Durrant
On Tue, Jul 7, 2020 at 3:05 PM Jürgen Groß <jgross@suse.com> wrote:
>
> On 06.07.20 20:16, Souptick Joarder wrote:
> > Previously, if lock_pages() end up partially mapping pages, it used
> > to return -ERRNO due to which unlock_pages() have to go through
> > each pages[i] till *nr_pages* to validate them. This can be avoided
> > by passing correct number of partially mapped pages & -ERRNO separately,
> > while returning from lock_pages() due to error.
> >
> > With this fix unlock_pages() doesn't need to validate pages[i] till
> > *nr_pages* for error scenario and few condition checks can be ignored.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> > Cc: John Hubbard <jhubbard@nvidia.com>
> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Cc: Paul Durrant <xadimgnik@gmail.com>
> > ---
> > drivers/xen/privcmd.c | 31 +++++++++++++++----------------
> > 1 file changed, 15 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> > index a250d11..33677ea 100644
> > --- a/drivers/xen/privcmd.c
> > +++ b/drivers/xen/privcmd.c
> > @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
> >
> > static int lock_pages(
> > struct privcmd_dm_op_buf kbufs[], unsigned int num,
> > - struct page *pages[], unsigned int nr_pages)
> > + struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
> > {
> > unsigned int i;
> > + int page_count = 0;
>
> Initial value shouldn't be needed, and ...
>
> >
> > for (i = 0; i < num; i++) {
> > unsigned int requested;
> > - int pinned;
>
> ... you could move the declaration here.
>
> With that done you can add my
>
> Reviewed-by: Juergen Gross <jgross@suse.com>
Ok. But does it going make any difference other than limiting scope ?
>
>
> Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-07 11:30 ` Souptick Joarder
@ 2020-07-07 11:43 ` Jürgen Groß
2020-07-07 19:30 ` John Hubbard
0 siblings, 1 reply; 14+ messages in thread
From: Jürgen Groß @ 2020-07-07 11:43 UTC (permalink / raw)
To: Souptick Joarder
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel,
John Hubbard, Paul Durrant
On 07.07.20 13:30, Souptick Joarder wrote:
> On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß <jgross@suse.com> wrote:
>>
>> On 06.07.20 20:16, Souptick Joarder wrote:
>>> pages need to be marked as dirty before unpinned it in
>>> unlock_pages() which was oversight. This is fixed now.
>>>
>>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
>>> Suggested-by: John Hubbard <jhubbard@nvidia.com>
>>> Cc: John Hubbard <jhubbard@nvidia.com>
>>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>>> Cc: Paul Durrant <xadimgnik@gmail.com>
>>> ---
>>> drivers/xen/privcmd.c | 5 ++++-
>>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>> index 33677ea..f6c1543 100644
>>> --- a/drivers/xen/privcmd.c
>>> +++ b/drivers/xen/privcmd.c
>>> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
>>> {
>>> unsigned int i;
>>>
>>> - for (i = 0; i < nr_pages; i++)
>>> + for (i = 0; i < nr_pages; i++) {
>>> + if (!PageDirty(pages[i]))
>>> + set_page_dirty_lock(pages[i]);
>>
>> With put_page() directly following I think you should be able to use
>> set_page_dirty() instead, as there is obviously a reference to the page
>> existing.
>
> Patch [3/3] will convert above codes to use unpin_user_pages_dirty_lock()
> which internally do the same check. So I thought to keep linux-stable and
> linux-next code in sync. John had a similar concern [1] and later agreed to keep
> this check.
>
> Shall I keep this check ? No ?
>
> [1] https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/
I wasn't referring to checking PageDirty(), but to the use of
set_page_dirty_lock().
Looking at the comment just before the implementation of
set_page_dirty_lock() suggests that it is fine to use set_page_dirty()
instead (so not calling lock_page()).
Only the transition from get_user_pages_fast() to pin_user_pages_fast()
requires to use the locked version IMO.
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path
2020-07-07 11:40 ` Souptick Joarder
@ 2020-07-07 11:45 ` Jürgen Groß
2020-07-08 2:07 ` Souptick Joarder
0 siblings, 1 reply; 14+ messages in thread
From: Jürgen Groß @ 2020-07-07 11:45 UTC (permalink / raw)
To: Souptick Joarder
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel,
John Hubbard, Paul Durrant
On 07.07.20 13:40, Souptick Joarder wrote:
> On Tue, Jul 7, 2020 at 3:05 PM Jürgen Groß <jgross@suse.com> wrote:
>>
>> On 06.07.20 20:16, Souptick Joarder wrote:
>>> Previously, if lock_pages() end up partially mapping pages, it used
>>> to return -ERRNO due to which unlock_pages() have to go through
>>> each pages[i] till *nr_pages* to validate them. This can be avoided
>>> by passing correct number of partially mapped pages & -ERRNO separately,
>>> while returning from lock_pages() due to error.
>>>
>>> With this fix unlock_pages() doesn't need to validate pages[i] till
>>> *nr_pages* for error scenario and few condition checks can be ignored.
>>>
>>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
>>> Cc: John Hubbard <jhubbard@nvidia.com>
>>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
>>> Cc: Paul Durrant <xadimgnik@gmail.com>
>>> ---
>>> drivers/xen/privcmd.c | 31 +++++++++++++++----------------
>>> 1 file changed, 15 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>> index a250d11..33677ea 100644
>>> --- a/drivers/xen/privcmd.c
>>> +++ b/drivers/xen/privcmd.c
>>> @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
>>>
>>> static int lock_pages(
>>> struct privcmd_dm_op_buf kbufs[], unsigned int num,
>>> - struct page *pages[], unsigned int nr_pages)
>>> + struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
>>> {
>>> unsigned int i;
>>> + int page_count = 0;
>>
>> Initial value shouldn't be needed, and ...
>>
>>>
>>> for (i = 0; i < num; i++) {
>>> unsigned int requested;
>>> - int pinned;
>>
>> ... you could move the declaration here.
>>
>> With that done you can add my
>>
>> Reviewed-by: Juergen Gross <jgross@suse.com>
>
> Ok. But does it going make any difference other than limiting scope ?
Dropping the initializer surely does, and in the end page_count just
replaces the former pinned variable, so why would we want to widen the
scope with this patch?
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*()
2020-07-06 18:16 ` [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*() Souptick Joarder
@ 2020-07-07 11:49 ` Jürgen Groß
0 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2020-07-07 11:49 UTC (permalink / raw)
To: Souptick Joarder, boris.ostrovsky, sstabellini
Cc: xen-devel, linux-kernel, John Hubbard, Paul Durrant
On 06.07.20 20:16, Souptick Joarder wrote:
> In 2019, we introduced pin_user_pages*() and now we are converting
> get_user_pages*() to the new API as appropriate. [1] & [2] could
> be referred for more information. This is case 5 as per document [1].
>
> [1] Documentation/core-api/pin_user_pages.rst
>
> [2] "Explicit pinning of user-space pages":
> https://lwn.net/Articles/807108/
>
> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Cc: Paul Durrant <xadimgnik@gmail.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-07 11:43 ` Jürgen Groß
@ 2020-07-07 19:30 ` John Hubbard
2020-07-08 5:40 ` Jürgen Groß
0 siblings, 1 reply; 14+ messages in thread
From: John Hubbard @ 2020-07-07 19:30 UTC (permalink / raw)
To: Jürgen Groß, Souptick Joarder
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel, Paul Durrant
On 2020-07-07 04:43, Jürgen Groß wrote:
> On 07.07.20 13:30, Souptick Joarder wrote:
>> On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß <jgross@suse.com> wrote:
...
>>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>>> index 33677ea..f6c1543 100644
>>>> --- a/drivers/xen/privcmd.c
>>>> +++ b/drivers/xen/privcmd.c
>>>> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[], unsigned int nr_pages)
>>>> {
>>>> unsigned int i;
>>>>
>>>> - for (i = 0; i < nr_pages; i++)
>>>> + for (i = 0; i < nr_pages; i++) {
>>>> + if (!PageDirty(pages[i]))
>>>> + set_page_dirty_lock(pages[i]);
>>>
>>> With put_page() directly following I think you should be able to use
>>> set_page_dirty() instead, as there is obviously a reference to the page
>>> existing.
>>
>> Patch [3/3] will convert above codes to use unpin_user_pages_dirty_lock()
>> which internally do the same check. So I thought to keep linux-stable and
>> linux-next code in sync. John had a similar concern [1] and later agreed to keep
>> this check.
>>
>> Shall I keep this check ? No ?
It doesn't matter *too* much, because patch 3/3 fixes up everything by
changing it all to unpin_user_pages_dirty_lock(). However, there is something
to be said for having correct interim patches, too. :) Details:
>>
>> [1] https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/
>
> I wasn't referring to checking PageDirty(), but to the use of
> set_page_dirty_lock().
>
> Looking at the comment just before the implementation of
> set_page_dirty_lock() suggests that it is fine to use set_page_dirty()
> instead (so not calling lock_page()).
no no, that's a misreading of the comment. Unless this xen/privcmd code has
somehow taken a reference on page->mapping->host (which I do *not* think is
the case), then it is still racy to call set_page_dirty() here. Instead,
set_page_dirty_lock() should be used.
>
> Only the transition from get_user_pages_fast() to pin_user_pages_fast()
> requires to use the locked version IMO.
>
That's a different misunderstanding. :) pin_user_pages*() APIs are meant to be
functionally drop-in replacements for get_user_pages*(). Internally,
pin_user_pages*() functions do some additional tracking, but from a caller's
perspective, it should look the same. In other words, there is nothing
about pin_user_pages_fast() that requires set_page_dirty_lock() upon release.
The reason set_page_dirty_lock() was chosen is that there are very few
(none at all?) call sites that need to release and dirty a page, that also meet
the requirements to safely call set_page_dirty().
That's why there is a unpin_user_pages_dirty_lock(), but there is not a
corresponding unpin_user_pages_dirty() call: the latter has not been required
so far, even though the call site conversions are nearly done.
thanks,
--
John Hubbard
NVIDIA
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 1/3] xen/privcmd: Corrected error handling path
2020-07-07 11:45 ` Jürgen Groß
@ 2020-07-08 2:07 ` Souptick Joarder
0 siblings, 0 replies; 14+ messages in thread
From: Souptick Joarder @ 2020-07-08 2:07 UTC (permalink / raw)
To: Jürgen Groß
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel,
John Hubbard, Paul Durrant
On Tue, Jul 7, 2020 at 5:15 PM Jürgen Groß <jgross@suse.com> wrote:
>
> On 07.07.20 13:40, Souptick Joarder wrote:
> > On Tue, Jul 7, 2020 at 3:05 PM Jürgen Groß <jgross@suse.com> wrote:
> >>
> >> On 06.07.20 20:16, Souptick Joarder wrote:
> >>> Previously, if lock_pages() end up partially mapping pages, it used
> >>> to return -ERRNO due to which unlock_pages() have to go through
> >>> each pages[i] till *nr_pages* to validate them. This can be avoided
> >>> by passing correct number of partially mapped pages & -ERRNO separately,
> >>> while returning from lock_pages() due to error.
> >>>
> >>> With this fix unlock_pages() doesn't need to validate pages[i] till
> >>> *nr_pages* for error scenario and few condition checks can be ignored.
> >>>
> >>> Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
> >>> Cc: John Hubbard <jhubbard@nvidia.com>
> >>> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> >>> Cc: Paul Durrant <xadimgnik@gmail.com>
> >>> ---
> >>> drivers/xen/privcmd.c | 31 +++++++++++++++----------------
> >>> 1 file changed, 15 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> >>> index a250d11..33677ea 100644
> >>> --- a/drivers/xen/privcmd.c
> >>> +++ b/drivers/xen/privcmd.c
> >>> @@ -580,13 +580,13 @@ static long privcmd_ioctl_mmap_batch(
> >>>
> >>> static int lock_pages(
> >>> struct privcmd_dm_op_buf kbufs[], unsigned int num,
> >>> - struct page *pages[], unsigned int nr_pages)
> >>> + struct page *pages[], unsigned int nr_pages, unsigned int *pinned)
> >>> {
> >>> unsigned int i;
> >>> + int page_count = 0;
> >>
> >> Initial value shouldn't be needed, and ...
> >>
> >>>
> >>> for (i = 0; i < num; i++) {
> >>> unsigned int requested;
> >>> - int pinned;
> >>
> >> ... you could move the declaration here.
> >>
> >> With that done you can add my
> >>
> >> Reviewed-by: Juergen Gross <jgross@suse.com>
> >
> > Ok. But does it going make any difference other than limiting scope ?
>
> Dropping the initializer surely does, and in the end page_count just
> replaces the former pinned variable, so why would we want to widen the
> scope with this patch?
Agree, no reason to move it up. Will change it in v3.
>
>
> Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v2 2/3] xen/privcmd: Mark pages as dirty
2020-07-07 19:30 ` John Hubbard
@ 2020-07-08 5:40 ` Jürgen Groß
0 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2020-07-08 5:40 UTC (permalink / raw)
To: John Hubbard, Souptick Joarder
Cc: Boris Ostrovsky, sstabellini, xen-devel, linux-kernel, Paul Durrant
On 07.07.20 21:30, John Hubbard wrote:
> On 2020-07-07 04:43, Jürgen Groß wrote:
>> On 07.07.20 13:30, Souptick Joarder wrote:
>>> On Tue, Jul 7, 2020 at 3:08 PM Jürgen Groß <jgross@suse.com> wrote:
> ...
>>>>> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
>>>>> index 33677ea..f6c1543 100644
>>>>> --- a/drivers/xen/privcmd.c
>>>>> +++ b/drivers/xen/privcmd.c
>>>>> @@ -612,8 +612,11 @@ static void unlock_pages(struct page *pages[],
>>>>> unsigned int nr_pages)
>>>>> {
>>>>> unsigned int i;
>>>>>
>>>>> - for (i = 0; i < nr_pages; i++)
>>>>> + for (i = 0; i < nr_pages; i++) {
>>>>> + if (!PageDirty(pages[i]))
>>>>> + set_page_dirty_lock(pages[i]);
>>>>
>>>> With put_page() directly following I think you should be able to use
>>>> set_page_dirty() instead, as there is obviously a reference to the page
>>>> existing.
>>>
>>> Patch [3/3] will convert above codes to use
>>> unpin_user_pages_dirty_lock()
>>> which internally do the same check. So I thought to keep linux-stable
>>> and
>>> linux-next code in sync. John had a similar concern [1] and later
>>> agreed to keep
>>> this check.
>>>
>>> Shall I keep this check ? No ?
>
> It doesn't matter *too* much, because patch 3/3 fixes up everything by
> changing it all to unpin_user_pages_dirty_lock(). However, there is
> something
> to be said for having correct interim patches, too. :) Details:
>
>>>
>>> [1]
>>> https://lore.kernel.org/xen-devel/a750e5e5-fd5d-663b-c5fd-261d7c939ba7@nvidia.com/
>>>
>>
>> I wasn't referring to checking PageDirty(), but to the use of
>> set_page_dirty_lock().
>>
>> Looking at the comment just before the implementation of
>> set_page_dirty_lock() suggests that it is fine to use set_page_dirty()
>> instead (so not calling lock_page()).
>
>
> no no, that's a misreading of the comment. Unless this xen/privcmd code has
> somehow taken a reference on page->mapping->host (which I do *not* think is
> the case), then it is still racy to call set_page_dirty() here. Instead,
> set_page_dirty_lock() should be used.
Ah, okay. Thanks for the clarification.
So you can add my
Reviewed-by: Juergen Gross <jgross@suse.com>
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2020-07-08 5:40 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-06 18:16 [PATCH v2 0/3] Few bug fixes and Convert to pin_user_pages*() Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 1/3] xen/privcmd: Corrected error handling path Souptick Joarder
2020-07-07 9:35 ` Jürgen Groß
2020-07-07 11:40 ` Souptick Joarder
2020-07-07 11:45 ` Jürgen Groß
2020-07-08 2:07 ` Souptick Joarder
2020-07-06 18:16 ` [PATCH v2 2/3] xen/privcmd: Mark pages as dirty Souptick Joarder
2020-07-07 9:38 ` Jürgen Groß
2020-07-07 11:30 ` Souptick Joarder
2020-07-07 11:43 ` Jürgen Groß
2020-07-07 19:30 ` John Hubbard
2020-07-08 5:40 ` Jürgen Groß
2020-07-06 18:16 ` [PATCH v2 3/3] xen/privcmd: Convert get_user_pages*() to pin_user_pages*() Souptick Joarder
2020-07-07 11:49 ` Jürgen Groß
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