Fixed MTP to work with TWRP

drivers/dma-buf/Makefile

@@ -0,0 +1 @@
+obj-y := dma-buf.o fence.o reservation.o seqno-fence.o

drivers/dma-buf/dma-buf.c

@@ -0,0 +1,929 @@
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/fence.h>
+#include <linux/anon_inodes.h>
+#include <linux/export.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/poll.h>
+#include <linux/reservation.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+struct dma_buf_list {
+	struct list_head head;
+	struct mutex lock;
+};
+
+static struct dma_buf_list db_list;
+
+static int dma_buf_release(struct inode *inode, struct file *file)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	BUG_ON(dmabuf->vmapping_counter);
+
+	/*
+	 * Any fences that a dma-buf poll can wait on should be signaled
+	 * before releasing dma-buf. This is the responsibility of each
+	 * driver that uses the reservation objects.
+	 *
+	 * If you hit this BUG() it means someone dropped their ref to the
+	 * dma-buf while still having pending operation to the buffer.
+	 */
+	BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
+
+	dmabuf->ops->release(dmabuf);
+
+	mutex_lock(&db_list.lock);
+	list_del(&dmabuf->list_node);
+	mutex_unlock(&db_list.lock);
+
+	if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])
+		reservation_object_fini(dmabuf->resv);
+
+	kfree(dmabuf);
+	return 0;
+}
+
+static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(file))
+		return -EINVAL;
+
+	dmabuf = file->private_data;
+
+	/* check for overflowing the buffer's size */
+	if (vma->vm_pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) >
+	    dmabuf->size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct dma_buf *dmabuf;
+	loff_t base;
+
+	if (!is_dma_buf_file(file))
+		return -EBADF;
+
+	dmabuf = file->private_data;
+
+	/* only support discovering the end of the buffer,
+	   but also allow SEEK_SET to maintain the idiomatic
+	   SEEK_END(0), SEEK_CUR(0) pattern */
+	if (whence == SEEK_END)
+		base = dmabuf->size;
+	else if (whence == SEEK_SET)
+		base = 0;
+	else
+		return -EINVAL;
+
+	if (offset != 0)
+		return -EINVAL;
+
+	return base + offset;
+}
+
+static void dma_buf_poll_cb(struct fence *fence, struct fence_cb *cb)
+{
+	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dcb->poll->lock, flags);
+	wake_up_locked_poll(dcb->poll, dcb->active);
+	dcb->active = 0;
+	spin_unlock_irqrestore(&dcb->poll->lock, flags);
+}
+
+static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
+{
+	struct dma_buf *dmabuf;
+	struct reservation_object *resv;
+	struct reservation_object_list *fobj;
+	struct fence *fence_excl;
+	unsigned long events;
+	unsigned shared_count, seq;
+
+	dmabuf = file->private_data;
+	if (!dmabuf || !dmabuf->resv)
+		return POLLERR;
+
+	resv = dmabuf->resv;
+
+	poll_wait(file, &dmabuf->poll, poll);
+
+	events = poll_requested_events(poll) & (POLLIN | POLLOUT);
+	if (!events)
+		return 0;
+
+retry:
+	seq = read_seqcount_begin(&resv->seq);
+	rcu_read_lock();
+
+	fobj = rcu_dereference(resv->fence);
+	if (fobj)
+		shared_count = fobj->shared_count;
+	else
+		shared_count = 0;
+	fence_excl = rcu_dereference(resv->fence_excl);
+	if (read_seqcount_retry(&resv->seq, seq)) {
+		rcu_read_unlock();
+		goto retry;
+	}
+
+	if (fence_excl && (!(events & POLLOUT) || shared_count == 0)) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
+		unsigned long pevents = POLLIN;
+
+		if (shared_count == 0)
+			pevents |= POLLOUT;
+
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active) {
+			dcb->active |= pevents;
+			events &= ~pevents;
+		} else
+			dcb->active = pevents;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (events & pevents) {
+			if (!fence_get_rcu(fence_excl)) {
+				/* force a recheck */
+				events &= ~pevents;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			} else if (!fence_add_callback(fence_excl, &dcb->cb,
+						       dma_buf_poll_cb)) {
+				events &= ~pevents;
+				fence_put(fence_excl);
+			} else {
+				/*
+				 * No callback queued, wake up any additional
+				 * waiters.
+				 */
+				fence_put(fence_excl);
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			}
+		}
+	}
+
+	if ((events & POLLOUT) && shared_count > 0) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
+		int i;
+
+		/* Only queue a new callback if no event has fired yet */
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active)
+			events &= ~POLLOUT;
+		else
+			dcb->active = POLLOUT;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (!(events & POLLOUT))
+			goto out;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct fence *fence = rcu_dereference(fobj->shared[i]);
+
+			if (!fence_get_rcu(fence)) {
+				/*
+				 * fence refcount dropped to zero, this means
+				 * that fobj has been freed
+				 *
+				 * call dma_buf_poll_cb and force a recheck!
+				 */
+				events &= ~POLLOUT;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+				break;
+			}
+			if (!fence_add_callback(fence, &dcb->cb,
+						dma_buf_poll_cb)) {
+				fence_put(fence);
+				events &= ~POLLOUT;
+				break;
+			}
+			fence_put(fence);
+		}
+
+		/* No callback queued, wake up any additional waiters. */
+		if (i == shared_count)
+			dma_buf_poll_cb(NULL, &dcb->cb);
+	}
+
+out:
+	rcu_read_unlock();
+	return events;
+}
+
+static const struct file_operations dma_buf_fops = {
+	.release	= dma_buf_release,
+	.mmap		= dma_buf_mmap_internal,
+	.llseek		= dma_buf_llseek,
+	.poll		= dma_buf_poll,
+};
+
+/*
+ * is_dma_buf_file - Check if struct file* is associated with dma_buf
+ */
+static inline int is_dma_buf_file(struct file *file)
+{
+	return file->f_op == &dma_buf_fops;
+}
+
+/**
+ * get_dma_buf_file - Finds dma_buf from a file descriptor
+ *
+ * @filp: [in] file descriptor to extract dma_buf.
+ *
+ * Returns the pointer to dma_buf stored in @filp after incrementing count.
+ * The returned dma_buf must be released with dma_buf_put().
+ * Returns NULL if @filp is not the file descriptor of dma_buf.
+ */
+struct dma_buf *get_dma_buf_file(struct file *filp)
+{
+	struct dma_buf *dmabuf;
+
+	if (!is_dma_buf_file(filp))
+		return NULL;
+
+	dmabuf = filp->private_data;
+
+	get_dma_buf(dmabuf);
+
+	return dmabuf;
+}
+/**
+ * dma_buf_export_named - Creates a new dma_buf, and associates an anon file
+ * with this buffer, so it can be exported.
+ * Also connect the allocator specific data and ops to the buffer.
+ * Additionally, provide a name string for exporter; useful in debugging.
+ *
+ * @priv:	[in]	Attach private data of allocator to this buffer
+ * @ops:	[in]	Attach allocator-defined dma buf ops to the new buffer.
+ * @size:	[in]	Size of the buffer
+ * @flags:	[in]	mode flags for the file.
+ * @exp_name:	[in]	name of the exporting module - useful for debugging.
+ * @resv:	[in]	reservation-object, NULL to allocate default one.
+ *
+ * Returns, on success, a newly created dma_buf object, which wraps the
+ * supplied private data and operations for dma_buf_ops. On either missing
+ * ops, or error in allocating struct dma_buf, will return negative error.
+ *
+ */
+struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
+				size_t size, int flags, const char *exp_name,
+				struct reservation_object *resv)
+{
+	struct dma_buf *dmabuf;
+	struct file *file;
+	size_t alloc_size = sizeof(struct dma_buf);
+	if (!resv)
+		alloc_size += sizeof(struct reservation_object);
+	else
+		/* prevent &dma_buf[1] == dma_buf->resv */
+		alloc_size += 1;
+
+	if (WARN_ON(!priv || !ops
+			  || !ops->map_dma_buf
+			  || !ops->unmap_dma_buf
+			  || !ops->release
+			  || !ops->kmap_atomic
+			  || !ops->kmap
+			  || !ops->mmap)) {
+		return ERR_PTR(-EINVAL);
+	}
+
+	dmabuf = kzalloc(alloc_size, GFP_KERNEL);
+	if (dmabuf == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	dmabuf->priv = priv;
+	dmabuf->ops = ops;
+	dmabuf->size = size;
+	dmabuf->exp_name = exp_name;
+	init_waitqueue_head(&dmabuf->poll);
+	dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
+	dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
+
+	if (!resv) {
+		resv = (struct reservation_object *)&dmabuf[1];
+		reservation_object_init(resv);
+	}
+	dmabuf->resv = resv;
+
+	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
+	if (IS_ERR(file)) {
+		kfree(dmabuf);
+		return ERR_CAST(file);
+	}
+
+	file->f_mode |= FMODE_LSEEK;
+	dmabuf->file = file;
+
+	mutex_init(&dmabuf->lock);
+	INIT_LIST_HEAD(&dmabuf->attachments);
+
+	mutex_lock(&db_list.lock);
+	list_add(&dmabuf->list_node, &db_list.head);
+	mutex_unlock(&db_list.lock);
+
+	return dmabuf;
+}
+EXPORT_SYMBOL_GPL(dma_buf_export_named);
+
+
+/**
+ * dma_buf_fd - returns a file descriptor for the given dma_buf
+ * @dmabuf:	[in]	pointer to dma_buf for which fd is required.
+ * @flags:      [in]    flags to give to fd
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf, int flags)
+{
+	int fd;
+
+	if (!dmabuf || !dmabuf->file)
+		return -EINVAL;
+
+	fd = get_unused_fd_flags(flags);
+	if (fd < 0)
+		return fd;
+
+	fd_install(fd, dmabuf->file);
+
+	return fd;
+}
+EXPORT_SYMBOL_GPL(dma_buf_fd);
+
+/**
+ * dma_buf_get - returns the dma_buf structure related to an fd
+ * @fd:	[in]	fd associated with the dma_buf to be returned
+ *
+ * On success, returns the dma_buf structure associated with an fd; uses
+ * file's refcounting done by fget to increase refcount. returns ERR_PTR
+ * otherwise.
+ */
+struct dma_buf *dma_buf_get(int fd)
+{
+	struct file *file;
+
+	file = fget(fd);
+
+	if (!file)
+		return ERR_PTR(-EBADF);
+
+	if (!is_dma_buf_file(file)) {
+		fput(file);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return file->private_data;
+}
+EXPORT_SYMBOL_GPL(dma_buf_get);
+
+/**
+ * dma_buf_put - decreases refcount of the buffer
+ * @dmabuf:	[in]	buffer to reduce refcount of
+ *
+ * Uses file's refcounting done implicitly by fput()
+ */
+void dma_buf_put(struct dma_buf *dmabuf)
+{
+	if (WARN_ON(!dmabuf || !dmabuf->file))
+		return;
+
+	fput(dmabuf->file);
+}
+EXPORT_SYMBOL_GPL(dma_buf_put);
+
+/**
+ * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
+ * calls attach() of dma_buf_ops to allow device-specific attach functionality
+ * @dmabuf:	[in]	buffer to attach device to.
+ * @dev:	[in]	device to be attached.
+ *
+ * Returns struct dma_buf_attachment * for this attachment; returns ERR_PTR on
+ * error.
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+					  struct device *dev)
+{
+	struct dma_buf_attachment *attach;
+	int ret;
+
+	if (WARN_ON(!dmabuf || !dev))
+		return ERR_PTR(-EINVAL);
+
+	attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
+	if (attach == NULL)
+		return ERR_PTR(-ENOMEM);
+
+	attach->dev = dev;
+	attach->dmabuf = dmabuf;
+
+	mutex_lock(&dmabuf->lock);
+
+	if (dmabuf->ops->attach) {
+		ret = dmabuf->ops->attach(dmabuf, dev, attach);
+		if (ret)
+			goto err_attach;
+	}
+	list_add(&attach->node, &dmabuf->attachments);
+
+	mutex_unlock(&dmabuf->lock);
+	return attach;
+
+err_attach:
+	kfree(attach);
+	mutex_unlock(&dmabuf->lock);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(dma_buf_attach);
+
+/**
+ * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
+ * optionally calls detach() of dma_buf_ops for device-specific detach
+ * @dmabuf:	[in]	buffer to detach from.
+ * @attach:	[in]	attachment to be detached; is free'd after this call.
+ *
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+	if (WARN_ON(!dmabuf || !attach))
+		return;
+
+	mutex_lock(&dmabuf->lock);
+	list_del(&attach->node);
+	if (dmabuf->ops->detach)
+		dmabuf->ops->detach(dmabuf, attach);
+
+	mutex_unlock(&dmabuf->lock);
+	kfree(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_detach);
+
+/**
+ * dma_buf_map_attachment - Returns the scatterlist table of the attachment;
+ * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the
+ * dma_buf_ops.
+ * @attach:	[in]	attachment whose scatterlist is to be returned
+ * @direction:	[in]	direction of DMA transfer
+ *
+ * Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
+ * on error.
+ */
+struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
+					enum dma_data_direction direction)
+{
+	struct sg_table *sg_table = ERR_PTR(-EINVAL);
+
+	might_sleep();
+
+	if (WARN_ON(!attach || !attach->dmabuf))
+		return ERR_PTR(-EINVAL);
+
+	sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
+	if (!sg_table)
+		sg_table = ERR_PTR(-ENOMEM);
+
+	return sg_table;
+}
+EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
+
+/**
+ * dma_buf_unmap_attachment - unmaps and decreases usecount of the buffer;might
+ * deallocate the scatterlist associated. Is a wrapper for unmap_dma_buf() of
+ * dma_buf_ops.
+ * @attach:	[in]	attachment to unmap buffer from
+ * @sg_table:	[in]	scatterlist info of the buffer to unmap
+ * @direction:  [in]    direction of DMA transfer
+ *
+ */
+void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
+				struct sg_table *sg_table,
+				enum dma_data_direction direction)
+{
+	might_sleep();
+
+	if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+		return;
+
+	attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
+						direction);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
+
+
+/**
+ * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the
+ * cpu in the kernel context. Calls begin_cpu_access to allow exporter-specific
+ * preparations. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf:	[in]	buffer to prepare cpu access for.
+ * @start:	[in]	start of range for cpu access.
+ * @len:	[in]	length of range for cpu access.
+ * @direction:	[in]	length of range for cpu access.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, size_t start, size_t len,
+			     enum dma_data_direction direction)
+{
+	int ret = 0;
+
+	if (WARN_ON(!dmabuf))
+		return -EINVAL;
+
+	if (dmabuf->ops->begin_cpu_access)
+		ret = dmabuf->ops->begin_cpu_access(dmabuf, start, len, direction);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access);
+
+/**
+ * dma_buf_end_cpu_access - Must be called after accessing a dma_buf from the
+ * cpu in the kernel context. Calls end_cpu_access to allow exporter-specific
+ * actions. Coherency is only guaranteed in the specified range for the
+ * specified access direction.
+ * @dmabuf:	[in]	buffer to complete cpu access for.
+ * @start:	[in]	start of range for cpu access.
+ * @len:	[in]	length of range for cpu access.
+ * @direction:	[in]	length of range for cpu access.
+ *
+ * This call must always succeed.
+ */
+void dma_buf_end_cpu_access(struct dma_buf *dmabuf, size_t start, size_t len,
+			    enum dma_data_direction direction)
+{
+	WARN_ON(!dmabuf);
+
+	if (dmabuf->ops->end_cpu_access)
+		dmabuf->ops->end_cpu_access(dmabuf, start, len, direction);
+}
+EXPORT_SYMBOL_GPL(dma_buf_end_cpu_access);
+
+/**
+ * dma_buf_kmap_atomic - Map a page of the buffer object into kernel address
+ * space. The same restrictions as for kmap_atomic and friends apply.
+ * @dmabuf:	[in]	buffer to map page from.
+ * @page_num:	[in]	page in PAGE_SIZE units to map.
+ *
+ * This call must always succeed, any necessary preparations that might fail
+ * need to be done in begin_cpu_access.
+ */
+void *dma_buf_kmap_atomic(struct dma_buf *dmabuf, unsigned long page_num)
+{
+	WARN_ON(!dmabuf);
+
+	return dmabuf->ops->kmap_atomic(dmabuf, page_num);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kmap_atomic);
+
+/**
+ * dma_buf_kunmap_atomic - Unmap a page obtained by dma_buf_kmap_atomic.
+ * @dmabuf:	[in]	buffer to unmap page from.
+ * @page_num:	[in]	page in PAGE_SIZE units to unmap.
+ * @vaddr:	[in]	kernel space pointer obtained from dma_buf_kmap_atomic.
+ *
+ * This call must always succeed.
+ */
+void dma_buf_kunmap_atomic(struct dma_buf *dmabuf, unsigned long page_num,
+			   void *vaddr)
+{
+	WARN_ON(!dmabuf);
+
+	if (dmabuf->ops->kunmap_atomic)
+		dmabuf->ops->kunmap_atomic(dmabuf, page_num, vaddr);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kunmap_atomic);
+
+/**
+ * dma_buf_kmap - Map a page of the buffer object into kernel address space. The
+ * same restrictions as for kmap and friends apply.
+ * @dmabuf:	[in]	buffer to map page from.
+ * @page_num:	[in]	page in PAGE_SIZE units to map.
+ *
+ * This call must always succeed, any necessary preparations that might fail
+ * need to be done in begin_cpu_access.
+ */
+void *dma_buf_kmap(struct dma_buf *dmabuf, unsigned long page_num)
+{
+	WARN_ON(!dmabuf);
+
+	return dmabuf->ops->kmap(dmabuf, page_num);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kmap);
+
+/**
+ * dma_buf_kunmap - Unmap a page obtained by dma_buf_kmap.
+ * @dmabuf:	[in]	buffer to unmap page from.
+ * @page_num:	[in]	page in PAGE_SIZE units to unmap.
+ * @vaddr:	[in]	kernel space pointer obtained from dma_buf_kmap.
+ *
+ * This call must always succeed.
+ */
+void dma_buf_kunmap(struct dma_buf *dmabuf, unsigned long page_num,
+		    void *vaddr)
+{
+	WARN_ON(!dmabuf);
+
+	if (dmabuf->ops->kunmap)
+		dmabuf->ops->kunmap(dmabuf, page_num, vaddr);
+}
+EXPORT_SYMBOL_GPL(dma_buf_kunmap);
+
+
+/**
+ * dma_buf_mmap - Setup up a userspace mmap with the given vma
+ * @dmabuf:	[in]	buffer that should back the vma
+ * @vma:	[in]	vma for the mmap
+ * @pgoff:	[in]	offset in pages where this mmap should start within the
+ * 			dma-buf buffer.
+ *
+ * This function adjusts the passed in vma so that it points at the file of the
+ * dma_buf operation. It also adjusts the starting pgoff and does bounds
+ * checking on the size of the vma. Then it calls the exporters mmap function to
+ * set up the mapping.
+ *
+ * Can return negative error values, returns 0 on success.
+ */
+int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
+		 unsigned long pgoff)
+{
+	struct file *oldfile;
+	int ret;
+
+	if (WARN_ON(!dmabuf || !vma))
+		return -EINVAL;
+
+	/* check for offset overflow */
+	if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) < pgoff)
+		return -EOVERFLOW;
+
+	/* check for overflowing the buffer's size */
+	if (pgoff + ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) >
+	    dmabuf->size >> PAGE_SHIFT)
+		return -EINVAL;
+
+	/* readjust the vma */
+	get_file(dmabuf->file);
+	oldfile = vma->vm_file;
+	vma->vm_file = dmabuf->file;
+	vma->vm_pgoff = pgoff;
+
+	ret = dmabuf->ops->mmap(dmabuf, vma);
+	if (ret) {
+		/* restore old parameters on failure */
+		vma->vm_file = oldfile;
+		fput(dmabuf->file);
+	} else {
+		if (oldfile)
+			fput(oldfile);
+	}
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(dma_buf_mmap);
+
+/**
+ * dma_buf_vmap - Create virtual mapping for the buffer object into kernel
+ * address space. Same restrictions as for vmap and friends apply.
+ * @dmabuf:	[in]	buffer to vmap
+ *
+ * This call may fail due to lack of virtual mapping address space.
+ * These calls are optional in drivers. The intended use for them
+ * is for mapping objects linear in kernel space for high use objects.
+ * Please attempt to use kmap/kunmap before thinking about these interfaces.
+ *
+ * Returns NULL on error.
+ */
+void *dma_buf_vmap(struct dma_buf *dmabuf)
+{
+	void *ptr;
+
+	if (WARN_ON(!dmabuf))
+		return NULL;
+
+	if (!dmabuf->ops->vmap)
+		return NULL;
+
+	mutex_lock(&dmabuf->lock);
+	if (dmabuf->vmapping_counter) {
+		dmabuf->vmapping_counter++;
+		BUG_ON(!dmabuf->vmap_ptr);
+		ptr = dmabuf->vmap_ptr;
+		goto out_unlock;
+	}
+
+	BUG_ON(dmabuf->vmap_ptr);
+
+	ptr = dmabuf->ops->vmap(dmabuf);
+	if (WARN_ON_ONCE(IS_ERR(ptr)))
+		ptr = NULL;
+	if (!ptr)
+		goto out_unlock;
+
+	dmabuf->vmap_ptr = ptr;
+	dmabuf->vmapping_counter = 1;
+
+out_unlock:
+	mutex_unlock(&dmabuf->lock);
+	return ptr;
+}
+EXPORT_SYMBOL_GPL(dma_buf_vmap);
+
+/**
+ * dma_buf_vunmap - Unmap a vmap obtained by dma_buf_vmap.
+ * @dmabuf:	[in]	buffer to vunmap
+ * @vaddr:	[in]	vmap to vunmap
+ */
+void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
+{
+	if (WARN_ON(!dmabuf))
+		return;
+
+	BUG_ON(!dmabuf->vmap_ptr);
+	BUG_ON(dmabuf->vmapping_counter == 0);
+	BUG_ON(dmabuf->vmap_ptr != vaddr);
+
+	mutex_lock(&dmabuf->lock);
+	if (--dmabuf->vmapping_counter == 0) {
+		if (dmabuf->ops->vunmap)
+			dmabuf->ops->vunmap(dmabuf, vaddr);
+		dmabuf->vmap_ptr = NULL;
+	}
+	mutex_unlock(&dmabuf->lock);
+}
+EXPORT_SYMBOL_GPL(dma_buf_vunmap);
+
+#ifdef CONFIG_DEBUG_FS
+static int dma_buf_describe(struct seq_file *s)
+{
+	int ret;
+	struct dma_buf *buf_obj;
+	struct dma_buf_attachment *attach_obj;
+	int count = 0, attach_count;
+	size_t size = 0;
+
+	ret = mutex_lock_interruptible(&db_list.lock);
+
+	if (ret)
+		return ret;
+
+	seq_puts(s, "\nDma-buf Objects:\n");
+	seq_puts(s, "size\tflags\tmode\tcount\texp_name\n");
+
+	list_for_each_entry(buf_obj, &db_list.head, list_node) {
+		ret = mutex_lock_interruptible(&buf_obj->lock);
+
+		if (ret) {
+			seq_puts(s,
+				 "\tERROR locking buffer object: skipping\n");
+			continue;
+		}
+
+		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\n",
+				buf_obj->size,
+				buf_obj->file->f_flags, buf_obj->file->f_mode,
+				file_count(buf_obj->file),
+				buf_obj->exp_name);
+
+		seq_puts(s, "\tAttached Devices:\n");
+		attach_count = 0;
+
+		list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
+			seq_puts(s, "\t");
+
+			seq_printf(s, "%s\n", dev_name(attach_obj->dev));
+			attach_count++;
+		}
+
+		seq_printf(s, "Total %d devices attached\n\n",
+				attach_count);
+
+		count++;
+		size += buf_obj->size;
+		mutex_unlock(&buf_obj->lock);
+	}
+
+	seq_printf(s, "\nTotal %d objects, %zu bytes\n", count, size);
+
+	mutex_unlock(&db_list.lock);
+	return 0;
+}
+
+static int dma_buf_show(struct seq_file *s, void *unused)
+{
+	void (*func)(struct seq_file *) = s->private;
+	func(s);
+	return 0;
+}
+
+static int dma_buf_debug_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, dma_buf_show, inode->i_private);
+}
+
+static const struct file_operations dma_buf_debug_fops = {
+	.open           = dma_buf_debug_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static struct dentry *dma_buf_debugfs_dir;
+
+static int dma_buf_init_debugfs(void)
+{
+	int err = 0;
+	dma_buf_debugfs_dir = debugfs_create_dir("dma_buf", NULL);
+	if (IS_ERR(dma_buf_debugfs_dir)) {
+		err = PTR_ERR(dma_buf_debugfs_dir);
+		dma_buf_debugfs_dir = NULL;
+		return err;
+	}
+
+	err = dma_buf_debugfs_create_file("bufinfo", dma_buf_describe);
+
+	if (err)
+		pr_debug("dma_buf: debugfs: failed to create node bufinfo\n");
+
+	return err;
+}
+
+static void dma_buf_uninit_debugfs(void)
+{
+	if (dma_buf_debugfs_dir)
+		debugfs_remove_recursive(dma_buf_debugfs_dir);
+}
+
+int dma_buf_debugfs_create_file(const char *name,
+				int (*write)(struct seq_file *))
+{
+	struct dentry *d;
+
+	d = debugfs_create_file(name, S_IRUGO, dma_buf_debugfs_dir,
+			write, &dma_buf_debug_fops);
+
+	return PTR_ERR_OR_ZERO(d);
+}
+#else
+static inline int dma_buf_init_debugfs(void)
+{
+	return 0;
+}
+static inline void dma_buf_uninit_debugfs(void)
+{
+}
+#endif
+
+static int __init dma_buf_init(void)
+{
+	mutex_init(&db_list.lock);
+	INIT_LIST_HEAD(&db_list.head);
+	dma_buf_init_debugfs();
+	return 0;
+}
+subsys_initcall(dma_buf_init);
+
+static void __exit dma_buf_deinit(void)
+{
+	dma_buf_uninit_debugfs();
+}
+__exitcall(dma_buf_deinit);

drivers/dma-buf/fence.c

@@ -0,0 +1,431 @@
+/*
+ * Fence mechanism for dma-buf and to allow for asynchronous dma access
+ *
+ * Copyright (C) 2012 Canonical Ltd
+ * Copyright (C) 2012 Texas Instruments
+ *
+ * Authors:
+ * Rob Clark <robdclark@gmail.com>
+ * Maarten Lankhorst <maarten.lankhorst@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/atomic.h>
+#include <linux/fence.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/fence.h>
+
+EXPORT_TRACEPOINT_SYMBOL(fence_annotate_wait_on);
+EXPORT_TRACEPOINT_SYMBOL(fence_emit);
+
+/*
+ * fence context counter: each execution context should have its own
+ * fence context, this allows checking if fences belong to the same
+ * context or not. One device can have multiple separate contexts,
+ * and they're used if some engine can run independently of another.
+ */
+static atomic_t fence_context_counter = ATOMIC_INIT(0);
+
+/**
+ * fence_context_alloc - allocate an array of fence contexts
+ * @num:	[in]	amount of contexts to allocate
+ *
+ * This function will return the first index of the number of fences allocated.
+ * The fence context is used for setting fence->context to a unique number.
+ */
+unsigned fence_context_alloc(unsigned num)
+{
+	BUG_ON(!num);
+	return atomic_add_return(num, &fence_context_counter) - num;
+}
+EXPORT_SYMBOL(fence_context_alloc);
+
+/**
+ * fence_signal_locked - signal completion of a fence
+ * @fence: the fence to signal
+ *
+ * Signal completion for software callbacks on a fence, this will unblock
+ * fence_wait() calls and run all the callbacks added with
+ * fence_add_callback(). Can be called multiple times, but since a fence
+ * can only go from unsignaled to signaled state, it will only be effective
+ * the first time.
+ *
+ * Unlike fence_signal, this function must be called with fence->lock held.
+ */
+int fence_signal_locked(struct fence *fence)
+{
+	struct fence_cb *cur, *tmp;
+	int ret = 0;
+
+	if (WARN_ON(!fence))
+		return -EINVAL;
+
+	if (!ktime_to_ns(fence->timestamp)) {
+		fence->timestamp = ktime_get();
+		smp_mb__before_atomic();
+	}
+
+	if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		ret = -EINVAL;
+
+		/*
+		 * we might have raced with the unlocked fence_signal,
+		 * still run through all callbacks
+		 */
+	} else
+		trace_fence_signaled(fence);
+
+	list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
+		list_del_init(&cur->node);
+		cur->func(fence, cur);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(fence_signal_locked);
+
+/**
+ * fence_signal - signal completion of a fence
+ * @fence: the fence to signal
+ *
+ * Signal completion for software callbacks on a fence, this will unblock
+ * fence_wait() calls and run all the callbacks added with
+ * fence_add_callback(). Can be called multiple times, but since a fence
+ * can only go from unsignaled to signaled state, it will only be effective
+ * the first time.
+ */
+int fence_signal(struct fence *fence)
+{
+	unsigned long flags;
+
+	if (!fence)
+		return -EINVAL;
+
+	if (!ktime_to_ns(fence->timestamp)) {
+		fence->timestamp = ktime_get();
+		smp_mb__before_atomic();
+	}
+
+	if (test_and_set_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		return -EINVAL;
+
+	trace_fence_signaled(fence);
+
+	if (test_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
+		struct fence_cb *cur, *tmp;
+
+		spin_lock_irqsave(fence->lock, flags);
+		list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
+			list_del_init(&cur->node);
+			cur->func(fence, cur);
+		}
+		spin_unlock_irqrestore(fence->lock, flags);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(fence_signal);
+
+/**
+ * fence_wait_timeout - sleep until the fence gets signaled
+ * or until timeout elapses
+ * @fence:	[in]	the fence to wait on
+ * @intr:	[in]	if true, do an interruptible wait
+ * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ *
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
+ * remaining timeout in jiffies on success. Other error values may be
+ * returned on custom implementations.
+ *
+ * Performs a synchronous wait on this fence. It is assumed the caller
+ * directly or indirectly (buf-mgr between reservation and committing)
+ * holds a reference to the fence, otherwise the fence might be
+ * freed before return, resulting in undefined behavior.
+ */
+signed long
+fence_wait_timeout(struct fence *fence, bool intr, signed long timeout)
+{
+	signed long ret;
+
+	if (WARN_ON(timeout < 0))
+		return -EINVAL;
+
+	trace_fence_wait_start(fence);
+	ret = fence->ops->wait(fence, intr, timeout);
+	trace_fence_wait_end(fence);
+	return ret;
+}
+EXPORT_SYMBOL(fence_wait_timeout);
+
+void fence_release(struct kref *kref)
+{
+	struct fence *fence =
+			container_of(kref, struct fence, refcount);
+
+	trace_fence_destroy(fence);
+
+	BUG_ON(!list_empty(&fence->cb_list));
+
+	if (fence->ops->release)
+		fence->ops->release(fence);
+	else
+		fence_free(fence);
+}
+EXPORT_SYMBOL(fence_release);
+
+void fence_free(struct fence *fence)
+{
+	kfree_rcu(fence, rcu);
+}
+EXPORT_SYMBOL(fence_free);
+
+/**
+ * fence_enable_sw_signaling - enable signaling on fence
+ * @fence:	[in]	the fence to enable
+ *
+ * this will request for sw signaling to be enabled, to make the fence
+ * complete as soon as possible
+ */
+void fence_enable_sw_signaling(struct fence *fence)
+{
+	unsigned long flags;
+
+	if (!test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags) &&
+	    !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		trace_fence_enable_signal(fence);
+
+		spin_lock_irqsave(fence->lock, flags);
+
+		if (!fence->ops->enable_signaling(fence))
+			fence_signal_locked(fence);
+
+		spin_unlock_irqrestore(fence->lock, flags);
+	}
+}
+EXPORT_SYMBOL(fence_enable_sw_signaling);
+
+/**
+ * fence_add_callback - add a callback to be called when the fence
+ * is signaled
+ * @fence:	[in]	the fence to wait on
+ * @cb:		[in]	the callback to register
+ * @func:	[in]	the function to call
+ *
+ * cb will be initialized by fence_add_callback, no initialization
+ * by the caller is required. Any number of callbacks can be registered
+ * to a fence, but a callback can only be registered to one fence at a time.
+ *
+ * Note that the callback can be called from an atomic context.  If
+ * fence is already signaled, this function will return -ENOENT (and
+ * *not* call the callback)
+ *
+ * Add a software callback to the fence. Same restrictions apply to
+ * refcount as it does to fence_wait, however the caller doesn't need to
+ * keep a refcount to fence afterwards: when software access is enabled,
+ * the creator of the fence is required to keep the fence alive until
+ * after it signals with fence_signal. The callback itself can be called
+ * from irq context.
+ *
+ */
+int fence_add_callback(struct fence *fence, struct fence_cb *cb,
+		       fence_func_t func)
+{
+	unsigned long flags;
+	int ret = 0;
+	bool was_set;
+
+	if (WARN_ON(!fence || !func))
+		return -EINVAL;
+
+	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		INIT_LIST_HEAD(&cb->node);
+		return -ENOENT;
+	}
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
+
+	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		ret = -ENOENT;
+	else if (!was_set) {
+		trace_fence_enable_signal(fence);
+
+		if (!fence->ops->enable_signaling(fence)) {
+			fence_signal_locked(fence);
+			ret = -ENOENT;
+		}
+	}
+
+	if (!ret) {
+		cb->func = func;
+		list_add_tail(&cb->node, &fence->cb_list);
+	} else
+		INIT_LIST_HEAD(&cb->node);
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(fence_add_callback);
+
+/**
+ * fence_remove_callback - remove a callback from the signaling list
+ * @fence:	[in]	the fence to wait on
+ * @cb:		[in]	the callback to remove
+ *
+ * Remove a previously queued callback from the fence. This function returns
+ * true if the callback is succesfully removed, or false if the fence has
+ * already been signaled.
+ *
+ * *WARNING*:
+ * Cancelling a callback should only be done if you really know what you're
+ * doing, since deadlocks and race conditions could occur all too easily. For
+ * this reason, it should only ever be done on hardware lockup recovery,
+ * with a reference held to the fence.
+ */
+bool
+fence_remove_callback(struct fence *fence, struct fence_cb *cb)
+{
+	unsigned long flags;
+	bool ret;
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	ret = !list_empty(&cb->node);
+	if (ret)
+		list_del_init(&cb->node);
+
+	spin_unlock_irqrestore(fence->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(fence_remove_callback);
+
+struct default_wait_cb {
+	struct fence_cb base;
+	struct task_struct *task;
+};
+
+static void
+fence_default_wait_cb(struct fence *fence, struct fence_cb *cb)
+{
+	struct default_wait_cb *wait =
+		container_of(cb, struct default_wait_cb, base);
+
+	wake_up_state(wait->task, TASK_NORMAL);
+}
+
+/**
+ * fence_default_wait - default sleep until the fence gets signaled
+ * or until timeout elapses
+ * @fence:	[in]	the fence to wait on
+ * @intr:	[in]	if true, do an interruptible wait
+ * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ *
+ * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
+ * remaining timeout in jiffies on success.
+ */
+signed long
+fence_default_wait(struct fence *fence, bool intr, signed long timeout)
+{
+	struct default_wait_cb cb;
+	unsigned long flags;
+	signed long ret = timeout;
+	bool was_set;
+
+	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		return timeout;
+
+	spin_lock_irqsave(fence->lock, flags);
+
+	if (intr && signal_pending(current)) {
+		ret = -ERESTARTSYS;
+		goto out;
+	}
+
+	was_set = test_and_set_bit(FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags);
+
+	if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+		goto out;
+
+	if (!was_set) {
+		trace_fence_enable_signal(fence);
+
+		if (!fence->ops->enable_signaling(fence)) {
+			fence_signal_locked(fence);
+			goto out;
+		}
+	}
+
+	cb.base.func = fence_default_wait_cb;
+	cb.task = current;
+	list_add(&cb.base.node, &fence->cb_list);
+
+	while (!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
+		if (intr)
+			__set_current_state(TASK_INTERRUPTIBLE);
+		else
+			__set_current_state(TASK_UNINTERRUPTIBLE);
+		spin_unlock_irqrestore(fence->lock, flags);
+
+		ret = schedule_timeout(ret);
+
+		spin_lock_irqsave(fence->lock, flags);
+		if (ret > 0 && intr && signal_pending(current))
+			ret = -ERESTARTSYS;
+	}
+
+	if (!list_empty(&cb.base.node))
+		list_del(&cb.base.node);
+	__set_current_state(TASK_RUNNING);
+
+out:
+	spin_unlock_irqrestore(fence->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(fence_default_wait);
+
+/**
+ * fence_init - Initialize a custom fence.
+ * @fence:	[in]	the fence to initialize
+ * @ops:	[in]	the fence_ops for operations on this fence
+ * @lock:	[in]	the irqsafe spinlock to use for locking this fence
+ * @context:	[in]	the execution context this fence is run on
+ * @seqno:	[in]	a linear increasing sequence number for this context
+ *
+ * Initializes an allocated fence, the caller doesn't have to keep its
+ * refcount after committing with this fence, but it will need to hold a
+ * refcount again if fence_ops.enable_signaling gets called. This can
+ * be used for other implementing other types of fence.
+ *
+ * context and seqno are used for easy comparison between fences, allowing
+ * to check which fence is later by simply using fence_later.
+ */
+void
+fence_init(struct fence *fence, const struct fence_ops *ops,
+	     spinlock_t *lock, unsigned context, unsigned seqno)
+{
+	BUG_ON(!lock);
+	BUG_ON(!ops || !ops->wait || !ops->enable_signaling ||
+	       !ops->get_driver_name || !ops->get_timeline_name);
+
+	kref_init(&fence->refcount);
+	fence->ops = ops;
+	INIT_LIST_HEAD(&fence->cb_list);
+	fence->lock = lock;
+	fence->context = context;
+	fence->seqno = seqno;
+	fence->flags = 0UL;
+
+	trace_fence_init(fence);
+}
+EXPORT_SYMBOL(fence_init);

drivers/dma-buf/reservation.c

@@ -0,0 +1,475 @@
+/*
+ * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
+ *
+ * Based on bo.c which bears the following copyright notice,
+ * but is dual licensed:
+ *
+ * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * 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 NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS 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.
+ *
+ **************************************************************************/
+/*
+ * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
+ */
+
+#include <linux/reservation.h>
+#include <linux/export.h>
+
+DEFINE_WW_CLASS(reservation_ww_class);
+EXPORT_SYMBOL(reservation_ww_class);
+
+struct lock_class_key reservation_seqcount_class;
+EXPORT_SYMBOL(reservation_seqcount_class);
+
+const char reservation_seqcount_string[] = "reservation_seqcount";
+EXPORT_SYMBOL(reservation_seqcount_string);
+/*
+ * Reserve space to add a shared fence to a reservation_object,
+ * must be called with obj->lock held.
+ */
+int reservation_object_reserve_shared(struct reservation_object *obj)
+{
+	struct reservation_object_list *fobj, *old;
+	u32 max;
+
+	old = reservation_object_get_list(obj);
+
+	if (old && old->shared_max) {
+		if (old->shared_count < old->shared_max) {
+			/* perform an in-place update */
+			kfree(obj->staged);
+			obj->staged = NULL;
+			return 0;
+		} else
+			max = old->shared_max * 2;
+	} else
+		max = 4;
+
+	/*
+	 * resize obj->staged or allocate if it doesn't exist,
+	 * noop if already correct size
+	 */
+	fobj = krealloc(obj->staged, offsetof(typeof(*fobj), shared[max]),
+			GFP_KERNEL);
+	if (!fobj)
+		return -ENOMEM;
+
+	obj->staged = fobj;
+	fobj->shared_max = max;
+	return 0;
+}
+EXPORT_SYMBOL(reservation_object_reserve_shared);
+
+static void
+reservation_object_add_shared_inplace(struct reservation_object *obj,
+				      struct reservation_object_list *fobj,
+				      struct fence *fence)
+{
+	u32 i;
+
+	fence_get(fence);
+
+	preempt_disable();
+	write_seqcount_begin(&obj->seq);
+
+	for (i = 0; i < fobj->shared_count; ++i) {
+		struct fence *old_fence;
+
+		old_fence = rcu_dereference_protected(fobj->shared[i],
+						reservation_object_held(obj));
+
+		if (old_fence->context == fence->context) {
+			/* memory barrier is added by write_seqcount_begin */
+			RCU_INIT_POINTER(fobj->shared[i], fence);
+			write_seqcount_end(&obj->seq);
+			preempt_enable();
+
+			fence_put(old_fence);
+			return;
+		}
+	}
+
+	/*
+	 * memory barrier is added by write_seqcount_begin,
+	 * fobj->shared_count is protected by this lock too
+	 */
+	RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
+	fobj->shared_count++;
+
+	write_seqcount_end(&obj->seq);
+	preempt_enable();
+}
+
+static void
+reservation_object_add_shared_replace(struct reservation_object *obj,
+				      struct reservation_object_list *old,
+				      struct reservation_object_list *fobj,
+				      struct fence *fence)
+{
+	unsigned i;
+	struct fence *old_fence = NULL;
+
+	fence_get(fence);
+
+	if (!old) {
+		RCU_INIT_POINTER(fobj->shared[0], fence);
+		fobj->shared_count = 1;
+		goto done;
+	}
+
+	/*
+	 * no need to bump fence refcounts, rcu_read access
+	 * requires the use of kref_get_unless_zero, and the
+	 * references from the old struct are carried over to
+	 * the new.
+	 */
+	fobj->shared_count = old->shared_count;
+
+	for (i = 0; i < old->shared_count; ++i) {
+		struct fence *check;
+
+		check = rcu_dereference_protected(old->shared[i],
+						reservation_object_held(obj));
+
+		if (!old_fence && check->context == fence->context) {
+			old_fence = check;
+			RCU_INIT_POINTER(fobj->shared[i], fence);
+		} else
+			RCU_INIT_POINTER(fobj->shared[i], check);
+	}
+	if (!old_fence) {
+		RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
+		fobj->shared_count++;
+	}
+
+done:
+	preempt_disable();
+	write_seqcount_begin(&obj->seq);
+	/*
+	 * RCU_INIT_POINTER can be used here,
+	 * seqcount provides the necessary barriers
+	 */
+	RCU_INIT_POINTER(obj->fence, fobj);
+	write_seqcount_end(&obj->seq);
+	preempt_enable();
+
+	if (old)
+		kfree_rcu(old, rcu);
+
+	if (old_fence)
+		fence_put(old_fence);
+}
+
+/*
+ * Add a fence to a shared slot, obj->lock must be held, and
+ * reservation_object_reserve_shared_fence has been called.
+ */
+void reservation_object_add_shared_fence(struct reservation_object *obj,
+					 struct fence *fence)
+{
+	struct reservation_object_list *old, *fobj = obj->staged;
+
+	old = reservation_object_get_list(obj);
+	obj->staged = NULL;
+
+	if (!fobj) {
+		BUG_ON(old->shared_count >= old->shared_max);
+		reservation_object_add_shared_inplace(obj, old, fence);
+	} else
+		reservation_object_add_shared_replace(obj, old, fobj, fence);
+}
+EXPORT_SYMBOL(reservation_object_add_shared_fence);
+
+void reservation_object_add_excl_fence(struct reservation_object *obj,
+				       struct fence *fence)
+{
+	struct fence *old_fence = reservation_object_get_excl(obj);
+	struct reservation_object_list *old;
+	u32 i = 0;
+
+	old = reservation_object_get_list(obj);
+	if (old)
+		i = old->shared_count;
+
+	if (fence)
+		fence_get(fence);
+
+	preempt_disable();
+	write_seqcount_begin(&obj->seq);
+	/* write_seqcount_begin provides the necessary memory barrier */
+	RCU_INIT_POINTER(obj->fence_excl, fence);
+	if (old)
+		old->shared_count = 0;
+	write_seqcount_end(&obj->seq);
+	preempt_enable();
+
+	/* inplace update, no shared fences */
+	while (i--)
+		fence_put(rcu_dereference_protected(old->shared[i],
+						reservation_object_held(obj)));
+
+	if (old_fence)
+		fence_put(old_fence);
+}
+EXPORT_SYMBOL(reservation_object_add_excl_fence);
+
+int reservation_object_get_fences_rcu(struct reservation_object *obj,
+				      struct fence **pfence_excl,
+				      unsigned *pshared_count,
+				      struct fence ***pshared)
+{
+	unsigned shared_count = 0;
+	unsigned retry = 1;
+	struct fence **shared = NULL, *fence_excl = NULL;
+	int ret = 0;
+
+	while (retry) {
+		struct reservation_object_list *fobj;
+		unsigned seq;
+
+		seq = read_seqcount_begin(&obj->seq);
+
+		rcu_read_lock();
+
+		fobj = rcu_dereference(obj->fence);
+		if (fobj) {
+			struct fence **nshared;
+			size_t sz = sizeof(*shared) * fobj->shared_max;
+
+			nshared = krealloc(shared, sz,
+					   GFP_NOWAIT | __GFP_NOWARN);
+			if (!nshared) {
+				rcu_read_unlock();
+				nshared = krealloc(shared, sz, GFP_KERNEL);
+				if (nshared) {
+					shared = nshared;
+					continue;
+				}
+
+				ret = -ENOMEM;
+				shared_count = 0;
+				break;
+			}
+			shared = nshared;
+			memcpy(shared, fobj->shared, sz);
+			shared_count = fobj->shared_count;
+		} else
+			shared_count = 0;
+		fence_excl = rcu_dereference(obj->fence_excl);
+
+		retry = read_seqcount_retry(&obj->seq, seq);
+		if (retry)
+			goto unlock;
+
+		if (!fence_excl || fence_get_rcu(fence_excl)) {
+			unsigned i;
+
+			for (i = 0; i < shared_count; ++i) {
+				if (fence_get_rcu(shared[i]))
+					continue;
+
+				/* uh oh, refcount failed, abort and retry */
+				while (i--)
+					fence_put(shared[i]);
+
+				if (fence_excl) {
+					fence_put(fence_excl);
+					fence_excl = NULL;
+				}
+
+				retry = 1;
+				break;
+			}
+		} else
+			retry = 1;
+
+unlock:
+		rcu_read_unlock();
+	}
+	*pshared_count = shared_count;
+	if (shared_count)
+		*pshared = shared;
+	else {
+		*pshared = NULL;
+		kfree(shared);
+	}
+	*pfence_excl = fence_excl;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
+
+long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
+					 bool wait_all, bool intr,
+					 unsigned long timeout)
+{
+	struct fence *fence;
+	unsigned seq, shared_count, i = 0;
+	long ret = timeout;
+
+retry:
+	fence = NULL;
+	shared_count = 0;
+	seq = read_seqcount_begin(&obj->seq);
+	rcu_read_lock();
+
+	if (wait_all) {
+		struct reservation_object_list *fobj = rcu_dereference(obj->fence);
+
+		if (fobj)
+			shared_count = fobj->shared_count;
+
+		if (read_seqcount_retry(&obj->seq, seq))
+			goto unlock_retry;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct fence *lfence = rcu_dereference(fobj->shared[i]);
+
+			if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
+				continue;
+
+			if (!fence_get_rcu(lfence))
+				goto unlock_retry;
+
+			if (fence_is_signaled(lfence)) {
+				fence_put(lfence);
+				continue;
+			}
+
+			fence = lfence;
+			break;
+		}
+	}
+
+	if (!shared_count) {
+		struct fence *fence_excl = rcu_dereference(obj->fence_excl);
+
+		if (read_seqcount_retry(&obj->seq, seq))
+			goto unlock_retry;
+
+		if (fence_excl &&
+		    !test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
+			if (!fence_get_rcu(fence_excl))
+				goto unlock_retry;
+
+			if (fence_is_signaled(fence_excl))
+				fence_put(fence_excl);
+			else
+				fence = fence_excl;
+		}
+	}
+
+	rcu_read_unlock();
+	if (fence) {
+		ret = fence_wait_timeout(fence, intr, ret);
+		fence_put(fence);
+		if (ret > 0 && wait_all && (i + 1 < shared_count))
+			goto retry;
+	}
+	return ret;
+
+unlock_retry:
+	rcu_read_unlock();
+	goto retry;
+}
+EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
+
+
+static inline int
+reservation_object_test_signaled_single(struct fence *passed_fence)
+{
+	struct fence *fence, *lfence = passed_fence;
+	int ret = 1;
+
+	if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
+		fence = fence_get_rcu(lfence);
+		if (!fence)
+			return -1;
+
+		ret = !!fence_is_signaled(fence);
+		fence_put(fence);
+	}
+	return ret;
+}
+
+bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
+					  bool test_all)
+{
+	unsigned seq, shared_count;
+	int ret = true;
+
+retry:
+	shared_count = 0;
+	seq = read_seqcount_begin(&obj->seq);
+	rcu_read_lock();
+
+	if (test_all) {
+		unsigned i;
+
+		struct reservation_object_list *fobj = rcu_dereference(obj->fence);
+
+		if (fobj)
+			shared_count = fobj->shared_count;
+
+		if (read_seqcount_retry(&obj->seq, seq))
+			goto unlock_retry;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct fence *fence = rcu_dereference(fobj->shared[i]);
+
+			ret = reservation_object_test_signaled_single(fence);
+			if (ret < 0)
+				goto unlock_retry;
+			else if (!ret)
+				break;
+		}
+
+		/*
+		 * There could be a read_seqcount_retry here, but nothing cares
+		 * about whether it's the old or newer fence pointers that are
+		 * signaled. That race could still have happened after checking
+		 * read_seqcount_retry. If you care, use ww_mutex_lock.
+		 */
+	}
+
+	if (!shared_count) {
+		struct fence *fence_excl = rcu_dereference(obj->fence_excl);
+
+		if (read_seqcount_retry(&obj->seq, seq))
+			goto unlock_retry;
+
+		if (fence_excl) {
+			ret = reservation_object_test_signaled_single(fence_excl);
+			if (ret < 0)
+				goto unlock_retry;
+		}
+	}
+
+	rcu_read_unlock();
+	return ret;
+
+unlock_retry:
+	rcu_read_unlock();
+	goto retry;
+}
+EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);

drivers/dma-buf/seqno-fence.c

@@ -0,0 +1,73 @@
+/*
+ * seqno-fence, using a dma-buf to synchronize fencing
+ *
+ * Copyright (C) 2012 Texas Instruments
+ * Copyright (C) 2012-2014 Canonical Ltd
+ * Authors:
+ *   Rob Clark <robdclark@gmail.com>
+ *   Maarten Lankhorst <maarten.lankhorst@canonical.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/seqno-fence.h>
+
+static const char *seqno_fence_get_driver_name(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->get_driver_name(fence);
+}
+
+static const char *seqno_fence_get_timeline_name(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->get_timeline_name(fence);
+}
+
+static bool seqno_enable_signaling(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->enable_signaling(fence);
+}
+
+static bool seqno_signaled(struct fence *fence)
+{
+	struct seqno_fence *seqno_fence = to_seqno_fence(fence);
+	return seqno_fence->ops->signaled && seqno_fence->ops->signaled(fence);
+}
+
+static void seqno_release(struct fence *fence)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+
+	dma_buf_put(f->sync_buf);
+	if (f->ops->release)
+		f->ops->release(fence);
+	else
+		fence_free(&f->base);
+}
+
+static signed long seqno_wait(struct fence *fence, bool intr, signed long timeout)
+{
+	struct seqno_fence *f = to_seqno_fence(fence);
+	return f->ops->wait(fence, intr, timeout);
+}
+
+const struct fence_ops seqno_fence_ops = {
+	.get_driver_name = seqno_fence_get_driver_name,
+	.get_timeline_name = seqno_fence_get_timeline_name,
+	.enable_signaling = seqno_enable_signaling,
+	.signaled = seqno_signaled,
+	.wait = seqno_wait,
+	.release = seqno_release,
+};
+EXPORT_SYMBOL(seqno_fence_ops);