| Message ID | 1597725140-8310-1-git-send-email-jrdr.linux@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] xen/gntdev.c: Convert get_user_pages*() to pin_user_pages*() | expand |
On 8/18/20 12:32 AM, 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> > --- > drivers/xen/gntdev.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c > index 64a9025a..e480509 100644 > --- a/drivers/xen/gntdev.c > +++ b/drivers/xen/gntdev.c > @@ -730,7 +730,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, > unsigned long xen_pfn; > int ret; > > - ret = get_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); > + ret = pin_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); > if (ret < 0) > return ret; > > @@ -744,10 +744,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, > > static void gntdev_put_pages(struct gntdev_copy_batch *batch) > { > - unsigned int i; > - > - for (i = 0; i < batch->nr_pages; i++) > - put_page(batch->pages[i]); > + unpin_user_pages(batch->pages, batch->nr_pages); There seems to be a bug in the original code (just like there was in privcmd.c that you fixed earlier) --- when gntdev_get_page() is called with writeable=true then the page needs to be marked dirty before being put. You can add a `bool writeable` to gntdev_copy_batch and set it in gntdev_grant_copy_seg() (and drop `writeable` argument to gntdev_get_page()) and then, based on batch->writeable, use either unpin_user_pages() or unpin_user_pages_dirty_lock(). (But to fix this in stable branches please make first patch call set_page_dirty_lock() for each page like you did in previous series) -boris > batch->nr_pages = 0; > } >
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 64a9025a..e480509 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -730,7 +730,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, unsigned long xen_pfn; int ret; - ret = get_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); + ret = pin_user_pages_fast(addr, 1, writeable ? FOLL_WRITE : 0, &page); if (ret < 0) return ret; @@ -744,10 +744,7 @@ static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, static void gntdev_put_pages(struct gntdev_copy_batch *batch) { - unsigned int i; - - for (i = 0; i < batch->nr_pages; i++) - put_page(batch->pages[i]); + unpin_user_pages(batch->pages, batch->nr_pages); batch->nr_pages = 0; }
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> --- drivers/xen/gntdev.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)