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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.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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>
Link: https://lkml.kernel.org/r/CAG48ez3SG6ngZLtasxJ6LABpOnqCz5-QHqb0B4k44TQ8F9n6+w@mail.gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jann Horn 2020-10-17 16:14:12 -07:00 committed by Linus Torvalds
parent fb8090b699
commit f3964599c2
1 changed files with 12 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
mm/gup_benchmark.c
View File

@ -72,6 +72,8 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
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(unsigned int cmd,
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(unsigned int cmd,
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(unsigned int cmd,
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;
}