IB/ipath: support for userspace apps using core driver

These files introduce a char device that userspace apps use to gain
direct memory-mapped access to the InfiniPath hardware, and routines for
pinning and unpinning user memory in cases where the hardware needs to
DMA into the user address space.
Signed-off-by: Bryan O'Sullivan <bos@pathscale.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_user_pages.c

+/*
+ * Copyright (c) 2003, 2004, 2005, 2006 PathScale, Inc. 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.
+ */
+
+#include <linux/mm.h>
+#include <linux/device.h>
+
+#include "ipath_kernel.h"
+
+static void __ipath_release_user_pages(struct page **p, size_t num_pages,
+				   int dirty)
+{
+	size_t i;
+
+	for (i = 0; i < num_pages; i++) {
+		ipath_cdbg(MM, "%lu/%lu put_page %p\n", (unsigned long) i,
+			   (unsigned long) num_pages, p[i]);
+		if (dirty)
+			set_page_dirty_lock(p[i]);
+		put_page(p[i]);
+	}
+}
+
+/* call with current->mm->mmap_sem held */
+static int __get_user_pages(unsigned long start_page, size_t num_pages,
+			struct page **p, struct vm_area_struct **vma)
+{
+	unsigned long lock_limit;
+	size_t got;
+	int ret;
+
+#if 0
+	/*
+	 * XXX - causes MPI programs to fail, haven't had time to check
+	 * yet
+	 */
+	if (!capable(CAP_IPC_LOCK)) {
+		ret = -EPERM;
+		goto bail;
+	}
+#endif
+
+	lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >>
+		PAGE_SHIFT;
+
+	if (num_pages > lock_limit) {
+		ret = -ENOMEM;
+		goto bail;
+	}
+
+	ipath_cdbg(VERBOSE, "pin %lx pages from vaddr %lx\n",
+		   (unsigned long) num_pages, start_page);
+
+	for (got = 0; got < num_pages; got += ret) {
+		ret = get_user_pages(current, current->mm,
+				     start_page + got * PAGE_SIZE,
+				     num_pages - got, 1, 1,
+				     p + got, vma);
+		if (ret < 0)
+			goto bail_release;
+	}
+
+	current->mm->locked_vm += num_pages;
+
+	ret = 0;
+	goto bail;
+
+bail_release:
+	__ipath_release_user_pages(p, got, 0);
+bail:
+	return ret;
+}
+
+/**
+ * ipath_get_user_pages - lock user pages into memory
+ * @start_page: the start page
+ * @num_pages: the number of pages
+ * @p: the output page structures
+ *
+ * This function takes a given start page (page aligned user virtual
+ * address) and pins it and the following specified number of pages.  For
+ * now, num_pages is always 1, but that will probably change at some point
+ * (because caller is doing expected sends on a single virtually contiguous
+ * buffer, so we can do all pages at once).
+ */
+int ipath_get_user_pages(unsigned long start_page, size_t num_pages,
+			 struct page **p)
+{
+	int ret;
+
+	down_write(&current->mm->mmap_sem);
+
+	ret = __get_user_pages(start_page, num_pages, p, NULL);
+
+	up_write(&current->mm->mmap_sem);
+
+	return ret;
+}
+
+/**
+ * ipath_get_user_pages_nocopy - lock a single page for I/O and mark shared
+ * @start_page: the page to lock
+ * @p: the output page structure
+ *
+ * This is similar to ipath_get_user_pages, but it's always one page, and we
+ * mark the page as locked for I/O, and shared.  This is used for the user
+ * process page that contains the destination address for the rcvhdrq tail
+ * update, so we need to have the vma. If we don't do this, the page can be
+ * taken away from us on fork, even if the child never touches it, and then
+ * the user process never sees the tail register updates.
+ */
+int ipath_get_user_pages_nocopy(unsigned long page, struct page **p)
+{
+	struct vm_area_struct *vma;
+	int ret;
+
+	down_write(&current->mm->mmap_sem);
+
+	ret = __get_user_pages(page, 1, p, &vma);
+
+	up_write(&current->mm->mmap_sem);
+
+	return ret;
+}
+
+void ipath_release_user_pages(struct page **p, size_t num_pages)
+{
+	down_write(&current->mm->mmap_sem);
+
+	__ipath_release_user_pages(p, num_pages, 1);
+
+	current->mm->locked_vm -= num_pages;
+
+	up_write(&current->mm->mmap_sem);
+}
+
+struct ipath_user_pages_work {
+	struct work_struct work;
+	struct mm_struct *mm;
+	unsigned long num_pages;
+};
+
+static void user_pages_account(void *ptr)
+{
+	struct ipath_user_pages_work *work = ptr;
+
+	down_write(&work->mm->mmap_sem);
+	work->mm->locked_vm -= work->num_pages;
+	up_write(&work->mm->mmap_sem);
+	mmput(work->mm);
+	kfree(work);
+}
+
+void ipath_release_user_pages_on_close(struct page **p, size_t num_pages)
+{
+	struct ipath_user_pages_work *work;
+	struct mm_struct *mm;
+
+	__ipath_release_user_pages(p, num_pages, 1);
+
+	mm = get_task_mm(current);
+	if (!mm)
+		goto bail;
+
+	work = kmalloc(sizeof(*work), GFP_KERNEL);
+	if (!work)
+		goto bail_mm;
+
+	goto bail;
+
+	INIT_WORK(&work->work, user_pages_account, work);
+	work->mm = mm;
+	work->num_pages = num_pages;
+
+bail_mm:
+	mmput(mm);
+bail:
+	return;
+}