diff options
author | Peter Xu <peterx@redhat.com> | 2020-09-25 18:25:57 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-09-27 11:21:35 -0700 |
commit | 008cfe4418b3dbda2ff820cdd7b1a5ce458ae444 (patch) | |
tree | fecd1175184b14d889738d6491a1cccf0b0a8ae5 /kernel/fork.c | |
parent | a1bffa48745afbb54cb4f873bba783b2ae8be042 (diff) |
mm: Introduce mm_struct.has_pinned
(Commit message majorly collected from Jason Gunthorpe)
Reduce the chance of false positive from page_maybe_dma_pinned() by
keeping track if the mm_struct has ever been used with pin_user_pages().
This allows cases that might drive up the page ref_count to avoid any
penalty from handling dma_pinned pages.
Future work is planned, to provide a more sophisticated solution, likely
to turn it into a real counter. For now, make it atomic_t but use it as
a boolean for simplicity.
Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r-- | kernel/fork.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 49677d668de4..e65d8192d080 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1011,6 +1011,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, mm_pgtables_bytes_init(mm); mm->map_count = 0; mm->locked_vm = 0; + atomic_set(&mm->has_pinned, 0); atomic64_set(&mm->pinned_vm, 0); memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); spin_lock_init(&mm->page_table_lock); |