On 10/7/20 9:44 AM, Daniel Vetter wrote:
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.
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Pawel Osciak <pawel@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Tomasz Figa <tfiga@xxxxxxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-samsung-soc@xxxxxxxxxxxxxxx
Cc: linux-media@xxxxxxxxxxxxxxx
---
mm/frame_vector.c | 36 +++++++++++-------------------------
1 file changed, 11 insertions(+), 25 deletions(-)
diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index 10f82d5643b6..39db520a51dc 100644
--- a/mm/frame_vector.c
+++ b/mm/frame_vector.c
@@ -38,7 +38,6 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
struct vm_area_struct *vma;
int ret = 0;
int err;
- int locked;
if (nr_frames == 0)
return 0;
@@ -48,35 +47,22 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
start = untagged_addr(start);
+ 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;
+ goto out_unlocked;
+ }
This part looks good, and changing to _fast is a potential performance improvement,
too.
+
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;
- }
Are you sure we don't need to check vma_is_fsdax() anymore?
-
- if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
- 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;
- }
-
vec->got_ref = false;
vec->is_pfns = true;
do {
@@ -101,8 +87,8 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
vma = find_vma_intersection(mm, start, start + 1);
} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
out:
- if (locked)
- mmap_read_unlock(mm);
+ mmap_read_unlock(mm);
+out_unlocked:
if (!ret)
ret = -EFAULT;
if (ret > 0)
All of the error handling still looks accurate there.
thanks,
--
John Hubbard
NVIDIA
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