[PATCH] mm/gup: might_lock_read(mmap_sem) in get_user_pages_fast()
From: John Hubbard
Date: Thu May 21 2020 - 21:04:52 EST
Instead of scattering these assertions across the drivers,
do this assertion inside the core of get_user_pages_fast*()
functions. That also includes pin_user_pages_fast*()
routines.
Add a might_lock_read(mmap_sem) call to internal_get_user_pages_fast().
Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
Hi Andrew,
This applies on top of [1], which in turn applies to
today's (20200521) linux-next.
As noted in the discussion [2], this will need changing from
mmap_sem to mmap_lock, after Michel Lespinasse's patchset
arrives.
[1]
https://lore.kernel.org/r/20200521233841.1279742-1-jhubbard@xxxxxxxxxx
[2] https://lore.kernel.org/linux-mm/20200520124817.GG31189@xxxxxxxx/
thanks,
John Hubbard
NVIDIA
mm/gup.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c
index ada6aa79576dc..3462c076e8ecf 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2728,6 +2728,9 @@ static int internal_get_user_pages_fast(unsigned long start, int nr_pages,
FOLL_FAST_ONLY)))
return -EINVAL;
+ if (!(gup_flags & FOLL_FAST_ONLY))
+ might_lock_read(¤t->mm->mmap_sem);
+
start = untagged_addr(start) & PAGE_MASK;
addr = start;
len = (unsigned long) nr_pages << PAGE_SHIFT;
--
2.26.2