This is my (failed) attempt to make the SYNC_* mandatory. I've tried to revoke write access to the mapped region until begin_cpu_access is called.
The tasklet schedule order seems alright but the whole logic is not working and I guess it's something related to the fs trick I'm trying to do with the put{,get}_write_access pair...
Not sure if I should follow this direction though. I've spent much time already on it!. What do you think?
Cc: Thomas Hellstrom thellstrom@vmware.com Cc: Jérôme Glisse jglisse@redhat.com
--- drivers/dma-buf/dma-buf.c | 31 ++++++++++++++++++++++++++++++- include/linux/dma-buf.h | 3 +++ 2 files changed, 33 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 9a298bd..06cb37b 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -75,14 +75,34 @@ static int dma_buf_release(struct inode *inode, struct file *file) if (dmabuf->resv == (struct reservation_object *)&dmabuf[1]) reservation_object_fini(dmabuf->resv);
+ tasklet_kill(&dmabuf->tasklet); + module_put(dmabuf->owner); kfree(dmabuf); return 0; }
+static void dmabuf_mmap_tasklet(unsigned long data) +{ + struct dma_buf *dmabuf = (struct dma_buf *) data; + struct inode *inode = file_inode(dmabuf->file); + + if (!inode) + return; + + /* the CPU accessing another device may put the cache in an incoherent state. + * Therefore if the mmap succeeds, we forbid any further write access to the + * dma-buf until SYNC_START ioctl takes place, which gets back the write + * access. */ + put_write_access(inode); + + inode_dio_wait(inode); +} + static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) { struct dma_buf *dmabuf; + int ret;
if (!is_dma_buf_file(file)) return -EINVAL; @@ -94,7 +114,11 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) dmabuf->size >> PAGE_SHIFT) return -EINVAL;
- return dmabuf->ops->mmap(dmabuf, vma); + ret = dmabuf->ops->mmap(dmabuf, vma); + if (!ret) + tasklet_schedule(&dmabuf->tasklet); + + return ret; }
static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) @@ -389,6 +413,8 @@ struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info) list_add(&dmabuf->list_node, &db_list.head); mutex_unlock(&db_list.lock);
+ tasklet_init(&dmabuf->tasklet, dmabuf_mmap_tasklet, (unsigned long) dmabuf); + return dmabuf; } EXPORT_SYMBOL_GPL(dma_buf_export); @@ -589,6 +615,7 @@ EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, enum dma_data_direction direction) { + struct inode *inode = file_inode(dmabuf->file); int ret = 0;
if (WARN_ON(!dmabuf)) @@ -597,6 +624,8 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, if (dmabuf->ops->begin_cpu_access) ret = dmabuf->ops->begin_cpu_access(dmabuf, direction);
+ get_write_access(inode); + return ret; } EXPORT_SYMBOL_GPL(dma_buf_begin_cpu_access); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 532108e..0359792 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -24,6 +24,7 @@ #ifndef __DMA_BUF_H__ #define __DMA_BUF_H__
+#include <linux/interrupt.h> #include <linux/file.h> #include <linux/err.h> #include <linux/scatterlist.h> @@ -118,6 +119,7 @@ struct dma_buf_ops { * @list_node: node for dma_buf accounting and debugging. * @priv: exporter specific private data for this buffer object. * @resv: reservation object linked to this dma-buf + * @tasklet: tasklet for deferred mmap tasks. */ struct dma_buf { size_t size; @@ -133,6 +135,7 @@ struct dma_buf { struct list_head list_node; void *priv; struct reservation_object *resv; + struct tasklet_struct tasklet;
/* poll support */ wait_queue_head_t poll;