Commit 87773dd5 authored Sep 03, 2014 by Shawn Bohrer Committed by Roland Dreier Sep 19, 2014

IB: ib_umem_release() should decrement mm->pinned_vm from ib_umem_get



In debugging an application that receives -ENOMEM from ib_reg_mr(), I
found that ib_umem_get() can fail because the pinned_vm count has
wrapped causing it to always be larger than the lock limit even with
RLIMIT_MEMLOCK set to RLIM_INFINITY.

The wrapping of pinned_vm occurs because the process that calls
ib_reg_mr() will have its mm->pinned_vm count incremented.  Later a
different process with a different mm_struct than the one that
allocated the ib_umem struct ends up releasing it which results in
decrementing the new processes mm->pinned_vm count past zero and
wrapping.

I'm not entirely sure what circumstances cause a different process to
release the ib_umem than the one that allocated it but the kernel
stack trace of the freeing process from my situation looks like the
following:

    Call Trace:
     [<ffffffff814d64b1>] dump_stack+0x19/0x1b
     [<ffffffffa0b522a5>] ib_umem_release+0x1f5/0x200 [ib_core]
     [<ffffffffa0b90681>] mlx4_ib_destroy_qp+0x241/0x440 [mlx4_ib]
     [<ffffffffa0b4d93c>] ib_destroy_qp+0x12c/0x170 [ib_core]
     [<ffffffffa0cc7129>] ib_uverbs_close+0x259/0x4e0 [ib_uverbs]
     [<ffffffff81141cba>] __fput+0xba/0x240
     [<ffffffff81141e4e>] ____fput+0xe/0x10
     [<ffffffff81060894>] task_work_run+0xc4/0xe0
     [<ffffffff810029e5>] do_notify_resume+0x95/0xa0
     [<ffffffff814e3dd0>] int_signal+0x12/0x17

The following patch fixes the issue by storing the pid struct of the
process that calls ib_umem_get() so that ib_umem_release and/or
ib_umem_account() can properly decrement the pinned_vm count of the
correct mm_struct.

Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

parent 52addcf9

drivers/infiniband/core/umem.c

+13 −6

Original line number	Diff line number	Diff line
		@@ -105,6 +105,7 @@ struct ib_umem ib_umem_get(struct ib_ucontext context, unsigned long addr,
		umem->length = size;
		umem->offset = addr & ~PAGE_MASK;
		umem->page_size = PAGE_SIZE;
		umem->pid = get_task_pid(current, PIDTYPE_PID);
		/*
		* We ask for writable memory if any access flags other than
		* "remote read" are set. "Local write" and "remote write"
		@@ -198,6 +199,7 @@ out:
		if (ret < 0) {
		if (need_release)
		__ib_umem_release(context->device, umem, 0);
		put_pid(umem->pid);
		kfree(umem);
		} else
		current->mm->pinned_vm = locked;
		@@ -230,15 +232,19 @@ void ib_umem_release(struct ib_umem *umem)
		{
		struct ib_ucontext *context = umem->context;
		struct mm_struct *mm;
		struct task_struct *task;
		unsigned long diff;

		__ib_umem_release(umem->context->device, umem, 1);

		mm = get_task_mm(current);
		if (!mm) {
		kfree(umem);
		return;
		}
		task = get_pid_task(umem->pid, PIDTYPE_PID);
		put_pid(umem->pid);
		if (!task)
		goto out;
		mm = get_task_mm(task);
		put_task_struct(task);
		if (!mm)
		goto out;

		diff = PAGE_ALIGN(umem->length + umem->offset) >> PAGE_SHIFT;

		@@ -262,9 +268,10 @@ void ib_umem_release(struct ib_umem *umem)
		} else
		down_write(&mm->mmap_sem);

		current->mm->pinned_vm -= diff;
		mm->pinned_vm -= diff;
		up_write(&mm->mmap_sem);
		mmput(mm);
		out:
		kfree(umem);
		}
		EXPORT_SYMBOL(ib_umem_release);

include/rdma/ib_umem.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,7 @@ struct ib_umem {
		int writable;
		int hugetlb;
		struct work_struct work;
		struct pid *pid;
		struct mm_struct *mm;
		unsigned long diff;
		struct sg_table sg_head;

Admin message