| Message ID | 20200529234309.484480-3-jhubbard@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vhost, docs: convert to pin_user_pages(), new "case 5" | expand |
On Fri 29-05-20 16:43:09, John Hubbard wrote: > This code was using get_user_pages*(), in approximately a "Case 5" > scenario (accessing the data within a page), using the categorization > from [1]. That means that it's time to convert the get_user_pages*() + > put_page() calls to pin_user_pages*() + unpin_user_pages() calls. > > There is some helpful background in [2]: basically, this is a small > part of fixing a long-standing disconnect between pinning pages, and > file systems' use of those pages. > > [1] Documentation/core-api/pin_user_pages.rst > > [2] "Explicit pinning of user-space pages": > https://lwn.net/Articles/807108/ > > Cc: Michael S. Tsirkin <mst@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Cc: kvm@vger.kernel.org > Cc: virtualization@lists.linux-foundation.org > Cc: netdev@vger.kernel.org > Signed-off-by: John Hubbard <jhubbard@nvidia.com> Looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > drivers/vhost/vhost.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 21a59b598ed8..596132a96cd5 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void __user *addr) > int bit = nr + (log % PAGE_SIZE) * 8; > int r; > > - r = get_user_pages_fast(log, 1, FOLL_WRITE, &page); > + r = pin_user_pages_fast(log, 1, FOLL_WRITE, &page); > if (r < 0) > return r; > BUG_ON(r != 1); > base = kmap_atomic(page); > set_bit(bit, base); > kunmap_atomic(base); > - set_page_dirty_lock(page); > - put_page(page); > + unpin_user_pages_dirty_lock(&page, 1, true); > return 0; > } > > -- > 2.26.2 >
On Fri, May 29, 2020 at 04:43:09PM -0700, John Hubbard wrote: > This code was using get_user_pages*(), in approximately a "Case 5" > scenario (accessing the data within a page), using the categorization > from [1]. That means that it's time to convert the get_user_pages*() + > put_page() calls to pin_user_pages*() + unpin_user_pages() calls. > > There is some helpful background in [2]: basically, this is a small > part of fixing a long-standing disconnect between pinning pages, and > file systems' use of those pages. > > [1] Documentation/core-api/pin_user_pages.rst > > [2] "Explicit pinning of user-space pages": > https://lwn.net/Articles/807108/ > > Cc: Michael S. Tsirkin <mst@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Cc: kvm@vger.kernel.org > Cc: virtualization@lists.linux-foundation.org > Cc: netdev@vger.kernel.org > Signed-off-by: John Hubbard <jhubbard@nvidia.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> > --- > drivers/vhost/vhost.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 21a59b598ed8..596132a96cd5 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void __user *addr) > int bit = nr + (log % PAGE_SIZE) * 8; > int r; > > - r = get_user_pages_fast(log, 1, FOLL_WRITE, &page); > + r = pin_user_pages_fast(log, 1, FOLL_WRITE, &page); > if (r < 0) > return r; > BUG_ON(r != 1); > base = kmap_atomic(page); > set_bit(bit, base); > kunmap_atomic(base); > - set_page_dirty_lock(page); > - put_page(page); > + unpin_user_pages_dirty_lock(&page, 1, true); > return 0; > } > > -- > 2.26.2
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 21a59b598ed8..596132a96cd5 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1762,15 +1762,14 @@ static int set_bit_to_user(int nr, void __user *addr) int bit = nr + (log % PAGE_SIZE) * 8; int r; - r = get_user_pages_fast(log, 1, FOLL_WRITE, &page); + r = pin_user_pages_fast(log, 1, FOLL_WRITE, &page); if (r < 0) return r; BUG_ON(r != 1); base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); - set_page_dirty_lock(page); - put_page(page); + unpin_user_pages_dirty_lock(&page, 1, true); return 0; }
This code was using get_user_pages*(), in approximately a "Case 5" scenario (accessing the data within a page), using the categorization from [1]. That means that it's time to convert the get_user_pages*() + put_page() calls to pin_user_pages*() + unpin_user_pages() calls. There is some helpful background in [2]: basically, this is a small part of fixing a long-standing disconnect between pinning pages, and file systems' use of those pages. [1] Documentation/core-api/pin_user_pages.rst [2] "Explicit pinning of user-space pages": https://lwn.net/Articles/807108/ Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: kvm@vger.kernel.org Cc: virtualization@lists.linux-foundation.org Cc: netdev@vger.kernel.org Signed-off-by: John Hubbard <jhubbard@nvidia.com> --- drivers/vhost/vhost.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)