From: Souptick Joarder <jrdr.li...@gmail.com> commit 779055842da5b2e508f3ccf9a8153cb1f704f566 upstream.
There seems to be a bug in the original code when gntdev_get_page() is called with writeable=true then the page needs to be marked dirty before being put. To address this, a bool writeable is added in gnt_dev_copy_batch, set it in gntdev_grant_copy_seg() (and drop `writeable` argument to gntdev_get_page()) and then, based on batch->writeable, use set_page_dirty_lock(). Fixes: a4cdb556cae0 (xen/gntdev: add ioctl for grant copy) Suggested-by: Boris Ostrovsky <boris.ostrov...@oracle.com> Signed-off-by: Souptick Joarder <jrdr.li...@gmail.com> Cc: John Hubbard <jhubb...@nvidia.com> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: Juergen Gross <jgr...@suse.com> Cc: David Vrabel <david.vra...@citrix.com> Cc: sta...@vger.kernel.org Link: https://lore.kernel.org/r/1599375114-32360-1-git-send-email-jrdr.li...@gmail.com Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com> Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com> [jinoh: backport accounting for missing commit 73b0140bf0fe ("mm/gup: change GUP fast to use flags rather than a write 'bool'")] Signed-off-by: Jinoh Kang <jinoh.kang...@gmail.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- drivers/xen/gntdev.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -842,17 +842,18 @@ struct gntdev_copy_batch { s16 __user *status[GNTDEV_COPY_BATCH]; unsigned int nr_ops; unsigned int nr_pages; + bool writeable; }; static int gntdev_get_page(struct gntdev_copy_batch *batch, void __user *virt, - bool writeable, unsigned long *gfn) + unsigned long *gfn) { unsigned long addr = (unsigned long)virt; struct page *page; unsigned long xen_pfn; int ret; - ret = get_user_pages_fast(addr, 1, writeable, &page); + ret = get_user_pages_fast(addr, 1, batch->writeable, &page); if (ret < 0) return ret; @@ -868,9 +869,13 @@ static void gntdev_put_pages(struct gntd { unsigned int i; - for (i = 0; i < batch->nr_pages; i++) + for (i = 0; i < batch->nr_pages; i++) { + if (batch->writeable && !PageDirty(batch->pages[i])) + set_page_dirty_lock(batch->pages[i]); put_page(batch->pages[i]); + } batch->nr_pages = 0; + batch->writeable = false; } static int gntdev_copy(struct gntdev_copy_batch *batch) @@ -959,8 +964,9 @@ static int gntdev_grant_copy_seg(struct virt = seg->source.virt + copied; off = (unsigned long)virt & ~XEN_PAGE_MASK; len = min(len, (size_t)XEN_PAGE_SIZE - off); + batch->writeable = false; - ret = gntdev_get_page(batch, virt, false, &gfn); + ret = gntdev_get_page(batch, virt, &gfn); if (ret < 0) return ret; @@ -978,8 +984,9 @@ static int gntdev_grant_copy_seg(struct virt = seg->dest.virt + copied; off = (unsigned long)virt & ~XEN_PAGE_MASK; len = min(len, (size_t)XEN_PAGE_SIZE - off); + batch->writeable = true; - ret = gntdev_get_page(batch, virt, true, &gfn); + ret = gntdev_get_page(batch, virt, &gfn); if (ret < 0) return ret;