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Subject[PATCH 4/4] mm/gup: introduce vaddr_pin_pages_remote(), and invoke it
Date
vaddr_pin_user_pages_remote() is the "vaddr_pin_pages" corresponding
variant to get_user_pages_remote(): it adds the ability to handle
FOLL_PIN, FOLL_LONGTERM, or both.

Note that the put_user_page*() requirement won't be truly required until
all of the call sites have been converted, and the tracking of pages is
activated.

Also, change process_vm_rw_single_vec() to invoke the new function.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
include/linux/mm.h | 5 +++++
mm/gup.c | 33 +++++++++++++++++++++++++++++++++
mm/process_vm_access.c | 23 ++++++++++++++---------
3 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6e7de424bf5e..849b509e9f89 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1606,6 +1606,11 @@ int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc,
long vaddr_pin_pages(unsigned long addr, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
struct vaddr_pin *vaddr_pin);
+long vaddr_pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ unsigned int gup_flags, struct page **pages,
+ struct vm_area_struct **vmas, int *locked,
+ struct vaddr_pin *vaddr_pin);
void vaddr_unpin_pages(struct page **pages, unsigned long nr_pages,
struct vaddr_pin *vaddr_pin, bool make_dirty);
bool mapping_inode_has_layout(struct vaddr_pin *vaddr_pin, struct page *page);
diff --git a/mm/gup.c b/mm/gup.c
index e49096d012ea..d7ce9b38178f 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2522,3 +2522,36 @@ void vaddr_unpin_pages(struct page **pages, unsigned long nr_pages,
__put_user_pages_dirty_lock(pages, nr_pages, make_dirty, vaddr_pin);
}
EXPORT_SYMBOL(vaddr_unpin_pages);
+
+/**
+ * vaddr_pin_user_pages_remote() - pin pages by virtual address and return the
+ * pages to the user.
+ *
+ * @tsk: the task_struct to use for page fault accounting, or
+ * NULL if faults are not to be recorded.
+ * @mm: mm_struct of target mm
+ * @addr: start address
+ * @nr_pages: number of pages to pin
+ * @gup_flags: flags to use for the pin. Please see FOLL_* documentation in
+ * mm.h.
+ * @pages: array of pages returned
+ * @vaddr_pin: If FOLL_LONGTERM is set, then vaddr_pin should point to an
+ * initialized struct that contains the owning mm and file. Otherwise, vaddr_pin
+ * should be set to NULL.
+ *
+ * This is the "vaddr_pin_pages" corresponding variant to
+ * get_user_pages_remote(), but with the ability to handle FOLL_PIN,
+ * FOLL_LONGTERM, or both.
+ */
+long vaddr_pin_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long start, unsigned long nr_pages,
+ unsigned int gup_flags, struct page **pages,
+ struct vm_area_struct **vmas, int *locked,
+ struct vaddr_pin *vaddr_pin)
+{
+ gup_flags |= FOLL_TOUCH | FOLL_REMOTE;
+
+ return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
+ locked, gup_flags, vaddr_pin);
+}
+EXPORT_SYMBOL(vaddr_pin_user_pages_remote);
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index 357aa7bef6c0..e08c1f760ad4 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -96,7 +96,7 @@ 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 +106,18 @@ 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);
+
+ flags |= FOLL_PIN;
+ pinned_pages = vaddr_pin_user_pages_remote(task, mm, pa,
+ pinned_pages, flags,
+ process_pages, NULL,
+ &locked, NULL);
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 +126,11 @@ 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: */
+ vaddr_unpin_pages(process_pages, pinned_pages, NULL, vm_write);
}

return rc;
--
2.22.1
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