[PATCH] IB uverbs: memory pinning implementation

Add support for pinning userspace memory regions and returning a list of pages
in the region.  This includes tracking pinned memory against vm_locked and
preventing unprivileged users from exceeding RLIMIT_MEMLOCK.
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/infiniband/core/uverbs_mem.c

+/*
+ * Copyright (c) 2005 Topspin Communications.  All rights reserved.
+ * Copyright (c) 2005 Cisco Systems.  All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ * $Id: uverbs_mem.c 2743 2005-06-28 22:27:59Z roland $
+ */
+
+#include <linux/mm.h>
+#include <linux/dma-mapping.h>
+
+#include "uverbs.h"
+
+struct ib_umem_account_work {
+	struct work_struct work;
+	struct mm_struct  *mm;
+	unsigned long      diff;
+};
+
+
+static void __ib_umem_release(struct ib_device *dev, struct ib_umem *umem, int dirty)
+{
+	struct ib_umem_chunk *chunk, *tmp;
+	int i;
+
+	list_for_each_entry_safe(chunk, tmp, &umem->chunk_list, list) {
+		dma_unmap_sg(dev->dma_device, chunk->page_list,
+			     chunk->nents, DMA_BIDIRECTIONAL);
+		for (i = 0; i < chunk->nents; ++i) {
+			if (umem->writable && dirty)
+				set_page_dirty_lock(chunk->page_list[i].page);
+			put_page(chunk->page_list[i].page);
+		}
+
+		kfree(chunk);
+	}
+}
+
+int ib_umem_get(struct ib_device *dev, struct ib_umem *mem,
+		void *addr, size_t size, int write)
+{
+	struct page **page_list;
+	struct ib_umem_chunk *chunk;
+	unsigned long locked;
+	unsigned long lock_limit;
+	unsigned long cur_base;
+	unsigned long npages;
+	int ret = 0;
+	int off;
+	int i;
+
+	if (!can_do_mlock())
+		return -EPERM;
+
+	page_list = (struct page **) __get_free_page(GFP_KERNEL);
+	if (!page_list)
+		return -ENOMEM;
+
+	mem->user_base = (unsigned long) addr;
+	mem->length    = size;
+	mem->offset    = (unsigned long) addr & ~PAGE_MASK;
+	mem->page_size = PAGE_SIZE;
+	mem->writable  = write;
+
+	INIT_LIST_HEAD(&mem->chunk_list);
+
+	npages = PAGE_ALIGN(size + mem->offset) >> PAGE_SHIFT;
+
+	down_write(&current->mm->mmap_sem);
+
+	locked     = npages + current->mm->locked_vm;
+	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
+
+	if ((locked > lock_limit) && !capable(CAP_IPC_LOCK)) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	cur_base = (unsigned long) addr & PAGE_MASK;
+
+	while (npages) {
+		ret = get_user_pages(current, current->mm, cur_base,
+				     min_t(int, npages,
+					   PAGE_SIZE / sizeof (struct page *)),
+				     1, !write, page_list, NULL);
+
+		if (ret < 0)
+			goto out;
+
+		cur_base += ret * PAGE_SIZE;
+		npages   -= ret;
+
+		off = 0;
+
+		while (ret) {
+			chunk = kmalloc(sizeof *chunk + sizeof (struct scatterlist) *
+					min_t(int, ret, IB_UMEM_MAX_PAGE_CHUNK),
+					GFP_KERNEL);
+			if (!chunk) {
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			chunk->nents = min_t(int, ret, IB_UMEM_MAX_PAGE_CHUNK);
+			for (i = 0; i < chunk->nents; ++i) {
+				chunk->page_list[i].page   = page_list[i + off];
+				chunk->page_list[i].offset = 0;
+				chunk->page_list[i].length = PAGE_SIZE;
+			}
+
+			chunk->nmap = dma_map_sg(dev->dma_device,
+						 &chunk->page_list[0],
+						 chunk->nents,
+						 DMA_BIDIRECTIONAL);
+			if (chunk->nmap <= 0) {
+				for (i = 0; i < chunk->nents; ++i)
+					put_page(chunk->page_list[i].page);
+				kfree(chunk);
+
+				ret = -ENOMEM;
+				goto out;
+			}
+
+			ret -= chunk->nents;
+			off += chunk->nents;
+			list_add_tail(&chunk->list, &mem->chunk_list);
+		}
+
+		ret = 0;
+	}
+
+out:
+	if (ret < 0)
+		__ib_umem_release(dev, mem, 0);
+	else
+		current->mm->locked_vm = locked;
+
+	up_write(&current->mm->mmap_sem);
+	free_page((unsigned long) page_list);
+
+	return ret;
+}
+
+void ib_umem_release(struct ib_device *dev, struct ib_umem *umem)
+{
+	__ib_umem_release(dev, umem, 1);
+
+	down_write(&current->mm->mmap_sem);
+	current->mm->locked_vm -=
+		PAGE_ALIGN(umem->length + umem->offset) >> PAGE_SHIFT;
+	up_write(&current->mm->mmap_sem);
+}
+
+static void ib_umem_account(void *work_ptr)
+{
+	struct ib_umem_account_work *work = work_ptr;
+
+	down_write(&work->mm->mmap_sem);
+	work->mm->locked_vm -= work->diff;
+	up_write(&work->mm->mmap_sem);
+	mmput(work->mm);
+	kfree(work);
+}
+
+void ib_umem_release_on_close(struct ib_device *dev, struct ib_umem *umem)
+{
+	struct ib_umem_account_work *work;
+	struct mm_struct *mm;
+
+	__ib_umem_release(dev, umem, 1);
+
+	mm = get_task_mm(current);
+	if (!mm)
+		return;
+
+	/*
+	 * We may be called with the mm's mmap_sem already held.  This
+	 * can happen when a userspace munmap() is the call that drops
+	 * the last reference to our file and calls our release
+	 * method.  If there are memory regions to destroy, we'll end
+	 * up here and not be able to take the mmap_sem.  Therefore we
+	 * defer the vm_locked accounting to the system workqueue.
+	 */
+
+	work = kmalloc(sizeof *work, GFP_KERNEL);
+	if (!work)
+		return;
+
+	INIT_WORK(&work->work, ib_umem_account, work);
+	work->mm   = mm;
+	work->diff = PAGE_ALIGN(umem->length + umem->offset) >> PAGE_SHIFT;
+
+	schedule_work(&work->work);
+}