Re: [PATCH 08/19] mm/process_vm_access: set FOLL_PIN via pin_user_pages_remote()

On 10/31/19 4:35 PM, Ira Weiny wrote:

On Wed, Oct 30, 2019 at 03:49:19PM -0700, John Hubbard wrote:

...

Convert process_vm_access to use the new pin_user_pages_remote() call, which sets FOLL_PIN. Setting FOLL_PIN is now required for code that requires tracking of pinned pages.

Also, release the pages via put_user_page*().

Also, rename "pages" to "pinned_pages", as this makes for easier reading of process_vm_rw_single_vec().

Ok... but it made review a bit harder...

Yes, sorry about that. After dealing with "pages means struct page *[]" for all this time, having an "int pages" just was a step too far for me here. :)

Thanks for working through it.

thanks,

John Hubbard NVIDIA

Reviewed-by: Ira Weiny ira.weiny@intel.com

...

Signed-off-by: John Hubbard jhubbard@nvidia.com

mm/process_vm_access.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c index 357aa7bef6c0..fd20ab675b85 100644 --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -42,12 +42,11 @@ static int process_vm_rw_pages(struct page **pages, if (copy > len) copy = len;

• if (vm_write) {
  

• if (vm_write)
  copied = copy_page_from_iter(page, offset, copy, iter);
  

• 	set_page_dirty_lock(page);
  

• } else {
  

• else
  copied = copy_page_to_iter(page, offset, copy, iter);
  

• }
  

• len -= copied; if (copied < copy && iov_iter_count(iter)) return -EFAULT;

@@ -96,7 +95,7 @@ static int process_vm_rw_single_vec(unsigned long addr, flags |= FOLL_WRITE; while (!rc && nr_pages && iov_iter_count(iter)) {

• int pages = min(nr_pages, max_pages_per_loop);
  

• int pinned_pages = min(nr_pages, max_pages_per_loop);
  

  int locked = 1; size_t bytes;

@@ -106,14 +105,15 @@ static int process_vm_rw_single_vec(unsigned long addr, * current/current->mm */ down_read(&mm->mmap_sem);

• pages = get_user_pages_remote(task, mm, pa, pages, flags,
  

• 			      process_pages, NULL, &locked);
  

• pinned_pages = pin_user_pages_remote(task, mm, pa, pinned_pages,
  

• 				     flags, process_pages,
  

• 				     NULL, &locked);
  

  if (locked) up_read(&mm->mmap_sem);

• if (pages <= 0)
  

• if (pinned_pages <= 0)
  return -EFAULT;
  

• bytes = pages * PAGE_SIZE - start_offset;
  

• bytes = pinned_pages * PAGE_SIZE - start_offset;
  

  if (bytes > len) bytes = len;

@@ -122,10 +122,12 @@ static int process_vm_rw_single_vec(unsigned long addr, vm_write); len -= bytes; start_offset = 0;

• nr_pages -= pages;
  

• pa += pages * PAGE_SIZE;
  

• while (pages)
  

• 	put_page(process_pages[--pages]);
  

• nr_pages -= pinned_pages;
  

• pa += pinned_pages * PAGE_SIZE;
  

• /* If vm_write is set, the pages need to be made dirty: */
  

• put_user_pages_dirty_lock(process_pages, pinned_pages,
  

• 			  vm_write);
  

  }

return rc; -- 2.23.0