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mm/frame-vector: Use FOLL_LONGTERM 

This is used by media/videbuf2 for persistent dma mappings, not just
for a single dma operation and then freed again, so needs
FOLL_LONGTERM.

Unfortunately current pup_locked doesn't support FOLL_LONGTERM due to
locking issues. Rework the code to pull the pup path out from the
mmap_sem critical section as suggested by Jason.

By relying entirely on the vma checks in pin_user_pages and follow_pfn
(for vm_flags and vma_is_fsdax) we can also streamline the code a lot.

Note that pin_user_pages_fast is a safe replacement despite the
seeming lack of checking for vma->vm_flasg & (VM_IO | VM_PFNMAP). Such
ptes are marked with pte_mkspecial (which pup_fast rejects in the
fastpath), and only architectures supporting that support the
pin_user_pages_fast fastpath.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Pawel Osciak <pawel@osciak.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: linux-mm@kvack.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: linux-media@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201127164131.2244124-6-daniel.vetter@ffwll.ch
master
Daniel Vetter 2020-11-27 17:41:19 +01:00
parent d88a0c169b
commit 04769cb1c4
3 changed files with 19 additions and 39 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
drivers/media/common/videobuf2/videobuf2-memops.c
View File

@ -40,7 +40,6 @@ struct frame_vector *vb2_create_framevec(unsigned long start,
unsigned long first, last;
unsigned long nr;
struct frame_vector *vec;
unsigned int flags = FOLL_FORCE | FOLL_WRITE;
first = start >> PAGE_SHIFT;
last = (start + length - 1) >> PAGE_SHIFT;
@ -48,7 +47,7 @@ struct frame_vector *vb2_create_framevec(unsigned long start,
vec = frame_vector_create(nr);
if (!vec)
return ERR_PTR(-ENOMEM);
ret = get_vaddr_frames(start & PAGE_MASK, nr, flags, vec);
ret = get_vaddr_frames(start & PAGE_MASK, nr, vec);
if (ret < 0)
goto out_destroy;
/* We accept only complete set of PFNs */

2
include/linux/mm.h
View File

@ -1768,7 +1768,7 @@ struct frame_vector {
struct frame_vector *frame_vector_create(unsigned int nr_frames);
void frame_vector_destroy(struct frame_vector *vec);
int get_vaddr_frames(unsigned long start, unsigned int nr_pfns,
unsigned int gup_flags, struct frame_vector *vec);
struct frame_vector *vec);
void put_vaddr_frames(struct frame_vector *vec);
int frame_vector_to_pages(struct frame_vector *vec);
void frame_vector_to_pfns(struct frame_vector *vec);

53
mm/frame_vector.c
View File

@ -32,13 +32,12 @@
* This function takes care of grabbing mmap_lock as necessary.
*/
int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
unsigned int gup_flags, struct frame_vector *vec)
struct frame_vector *vec)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
int ret = 0;
int err;
int locked;
if (nr_frames == 0)
return 0;
@ -48,40 +47,26 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
start = untagged_addr(start);
mmap_read_lock(mm);
locked = 1;
vma = find_vma_intersection(mm, start, start + 1);
if (!vma) {
ret = -EFAULT;
goto out;
}
/*
* While get_vaddr_frames() could be used for transient (kernel
* controlled lifetime) pinning of memory pages all current
* users establish long term (userspace controlled lifetime)
* page pinning. Treat get_vaddr_frames() like
* get_user_pages_longterm() and disallow it for filesystem-dax
* mappings.
*/
if (vma_is_fsdax(vma)) {
ret = -EOPNOTSUPP;
goto out;
}
if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
ret = pin_user_pages_fast(start, nr_frames,
FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
(struct page **)(vec->ptrs));
if (ret > 0) {
vec->got_ref = true;
vec->is_pfns = false;
ret = pin_user_pages_locked(start, nr_frames,
gup_flags, (struct page **)(vec->ptrs), &locked);
goto out;
goto out_unlocked;
}
mmap_read_lock(mm);
vec->got_ref = false;
vec->is_pfns = true;
ret = 0;
do {
unsigned long *nums = frame_vector_pfns(vec);
vma = find_vma_intersection(mm, start, start + 1);
if (!vma)
break;
while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
err = follow_pfn(vma, start, &nums[ret]);
if (err) {
@ -92,17 +77,13 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
start += PAGE_SIZE;
ret++;
}
/*
* We stop if we have enough pages or if VMA doesn't completely
* cover the tail page.
*/
if (ret >= nr_frames || start < vma->vm_end)
/* Bail out if VMA doesn't completely cover the tail page. */
if (start < vma->vm_end)
break;
vma = find_vma_intersection(mm, start, start + 1);
} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
} while (ret < nr_frames);
out:
if (locked)
mmap_read_unlock(mm);
mmap_read_unlock(mm);
out_unlocked:
if (!ret)
ret = -EFAULT;
if (ret > 0)