diff mbox series

[12/40] mm/gup_benchmark: take the mmap lock around GUP

Message ID 20201017231412.94CmEnsAR%akpm@linux-foundation.org (mailing list archive)
State New, archived
Headers show
Series [01/40] ia64: fix build error with !COREDUMP | expand

Commit Message

Andrew Morton Oct. 17, 2020, 11:14 p.m. UTC 
From: Jann Horn <jannh@google.com>
Subject: mm/gup_benchmark: take the mmap lock around GUP

To be safe against concurrent changes to the VMA tree, we must take the
mmap lock around GUP operations (excluding the GUP-fast family of
operations, which will take the mmap lock by themselves if necessary).

This code is only for testing, and it's only reachable by root through
debugfs, so this doesn't really have any impact; however, if we want to
add lockdep asserts into the GUP path, we need to have clean locking here.

Link: https://lkml.kernel.org/r/CAG48ez3SG6ngZLtasxJ6LABpOnqCz5-QHqb0B4k44TQ8F9n6+w@mail.gmail.com
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Michel Lespinasse <walken@google.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup_benchmark.c |   15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)
diff mbox series

Patch

--- a/mm/gup_benchmark.c~mm-gup_benchmark-take-the-mmap-lock-around-gup
+++ a/mm/gup_benchmark.c
@@ -72,6 +72,8 @@  static int __gup_benchmark_ioctl(unsigne
 	int nr;
 	struct page **pages;
 	int ret = 0;
+	bool needs_mmap_lock =
+		cmd != GUP_FAST_BENCHMARK && cmd != PIN_FAST_BENCHMARK;
 
 	if (gup->size > ULONG_MAX)
 		return -EINVAL;
@@ -81,6 +83,11 @@  static int __gup_benchmark_ioctl(unsigne
 	if (!pages)
 		return -ENOMEM;
 
+	if (needs_mmap_lock && mmap_read_lock_killable(current->mm)) {
+		ret = -EINTR;
+		goto free_pages;
+	}
+
 	i = 0;
 	nr = gup->nr_pages_per_call;
 	start_time = ktime_get();
@@ -120,9 +127,8 @@  static int __gup_benchmark_ioctl(unsigne
 					    pages + i, NULL);
 			break;
 		default:
-			kvfree(pages);
 			ret = -EINVAL;
-			goto out;
+			goto unlock;
 		}
 
 		if (nr <= 0)
@@ -150,8 +156,11 @@  static int __gup_benchmark_ioctl(unsigne
 	end_time = ktime_get();
 	gup->put_delta_usec = ktime_us_delta(end_time, start_time);
 
+unlock:
+	if (needs_mmap_lock)
+		mmap_read_unlock(current->mm);
+free_pages:
 	kvfree(pages);
-out:
 	return ret;
 }