mm->pinned_vm counts pages of mm's address space that were permanently pinned in memory by increasing their reference counter. The counter was introduced by commit bc3e53f682d9 ("mm: distinguish between mlocked and pinned pages"), while before it locked_vm had been used for such pages. Obviously, we should reset the counter on fork if !CLONE_VM, just like we do with locked_vm, but currently we don't. Let's fix it. This patch will fix the contents of /proc/pid/status:VmPin. ib_umem_get[infiniband] and perf_mmap still check pinned_vm against RLIMIT_MEMLOCK. It's left from the times when pinned pages were accounted under locked_vm, but today it looks wrong. It isn't clear how we should deal with it. We still have some drivers accounting pinned pages under mm->locked_vm - this is what commit bc3e53f682d9 was fighting against. It's infiniband/usnic and vfio.
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| @@ -543,6 +543,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p) · 542 unmodified lines | ||
| 543 | 543 | atomic_long_set(&mm->nr_ptes, 0); |
| 544 | 544 | mm->map_count = 0; |
| 545 | 545 | mm->locked_vm = 0; |
| 546 | + mm->pinned_vm = 0; | |
| 546 | 547 | memset(&mm->rss_stat, 0, sizeof(mm->rss_stat)); |
| 547 | 548 | spin_lock_init(&mm->page_table_lock); |
| 548 | 549 | mm_init_cpumask(mm); |