From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Setup a dax device.
Use the shm capability to find the cache entry and map it.
The DAX window is accessed by the fs/dax.c infrastructure and must have
struct pages (at least on x86). Use devm_memremap_pages() to map the
DAX window PCI BAR and allocate struct page.
Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx>
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@xxxxxxxxx>
Signed-off-by: Liu Bo <bo.liu@xxxxxxxxxxxxxxxxx>
---
fs/fuse/virtio_fs.c | 115 +++++++++++++++++++++++++++++++++
include/uapi/linux/virtio_fs.h | 3 +
2 files changed, 118 insertions(+)
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 62cdd6817b5b..b0574b208cd5 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -5,6 +5,9 @@
*/
#include <linux/fs.h>
+#include <linux/dax.h>
+#include <linux/pci.h>
+#include <linux/pfn_t.h>
#include <linux/module.h>
#include <linux/virtio.h>
#include <linux/virtio_fs.h>
@@ -50,6 +53,12 @@ struct virtio_fs {
struct virtio_fs_vq *vqs;
unsigned int nvqs; /* number of virtqueues */
unsigned int num_request_queues; /* number of request queues */
+ struct dax_device *dax_dev;
+
+ /* DAX memory window where file contents are mapped */
+ void *window_kaddr;
+ phys_addr_t window_phys_addr;
+ size_t window_len;
};
struct virtio_fs_forget_req {
@@ -690,6 +699,108 @@ static void virtio_fs_cleanup_vqs(struct virtio_device *vdev,
vdev->config->del_vqs(vdev);
}
+/* Map a window offset to a page frame number. The window offset will have
+ * been produced by .iomap_begin(), which maps a file offset to a window
+ * offset.
+ */
+static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+ long nr_pages, void **kaddr, pfn_t *pfn)
+{
+ struct virtio_fs *fs = dax_get_private(dax_dev);
+ phys_addr_t offset = PFN_PHYS(pgoff);
+ size_t max_nr_pages = fs->window_len/PAGE_SIZE - pgoff;
+
+ if (kaddr)
+ *kaddr = fs->window_kaddr + offset;
+ if (pfn)
+ *pfn = phys_to_pfn_t(fs->window_phys_addr + offset,
+ PFN_DEV | PFN_MAP);
+ return nr_pages > max_nr_pages ? max_nr_pages : nr_pages;
+}
+
+static size_t virtio_fs_copy_from_iter(struct dax_device *dax_dev,
+ pgoff_t pgoff, void *addr,
+ size_t bytes, struct iov_iter *i)
+{
+ return copy_from_iter(addr, bytes, i);
+}
+
+static size_t virtio_fs_copy_to_iter(struct dax_device *dax_dev,
+ pgoff_t pgoff, void *addr,
+ size_t bytes, struct iov_iter *i)
+{
+ return copy_to_iter(addr, bytes, i);
+}
+
+static const struct dax_operations virtio_fs_dax_ops = {
+ .direct_access = virtio_fs_direct_access,
+ .copy_from_iter = virtio_fs_copy_from_iter,
+ .copy_to_iter = virtio_fs_copy_to_iter,
+};
+
+static void virtio_fs_cleanup_dax(void *data)
+{
+ struct virtio_fs *fs = data;
+
+ kill_dax(fs->dax_dev);
+ put_dax(fs->dax_dev);
+}
+
+static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
+{
+ struct virtio_shm_region cache_reg;
+ struct dev_pagemap *pgmap;
+ bool have_cache;
+
+ if (!IS_ENABLED(CONFIG_DAX_DRIVER))
+ return 0;
+
+ /* Get cache region */
+ have_cache = virtio_get_shm_region(vdev, &cache_reg,
+ (u8)VIRTIO_FS_SHMCAP_ID_CACHE);
+ if (!have_cache) {
+ dev_notice(&vdev->dev, "%s: No cache capability\n", __func__);
+ return 0;
+ } else {
+ dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n",
+ cache_reg.len, cache_reg.addr);
+ }
+
+ pgmap = devm_kzalloc(&vdev->dev, sizeof(*pgmap), GFP_KERNEL);
+ if (!pgmap)
+ return -ENOMEM;
+
+ pgmap->type = MEMORY_DEVICE_FS_DAX;
+
+ /* Ideally we would directly use the PCI BAR resource but
+ * devm_memremap_pages() wants its own copy in pgmap. So
+ * initialize a struct resource from scratch (only the start
+ * and end fields will be used).
+ */
+ pgmap->res = (struct resource){
+ .name = "virtio-fs dax window",
+ .start = (phys_addr_t) cache_reg.addr,
+ .end = (phys_addr_t) cache_reg.addr + cache_reg.len - 1,
+ };
+
+ fs->window_kaddr = devm_memremap_pages(&vdev->dev, pgmap);
+ if (IS_ERR(fs->window_kaddr))
+ return PTR_ERR(fs->window_kaddr);
+
+ fs->window_phys_addr = (phys_addr_t) cache_reg.addr;
+ fs->window_len = (phys_addr_t) cache_reg.len;
+
+ dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx"
+ " len 0x%llx\n", __func__, fs->window_kaddr, cache_reg.addr,
+ cache_reg.len);
+
+ fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops, 0);
+ if (!fs->dax_dev)
+ return -ENOMEM;
+
+ return devm_add_action_or_reset(&vdev->dev, virtio_fs_cleanup_dax, fs);
+}
+
static int virtio_fs_probe(struct virtio_device *vdev)
{
struct virtio_fs *fs;
@@ -711,6 +822,10 @@ static int virtio_fs_probe(struct virtio_device *vdev)
/* TODO vq affinity */
+ ret = virtio_fs_setup_dax(vdev, fs);
+ if (ret < 0)
+ goto out_vqs;
+
/* Bring the device online in case the filesystem is mounted and
* requests need to be sent before we return.
*/
diff --git a/include/uapi/linux/virtio_fs.h b/include/uapi/linux/virtio_fs.h
index b02eb2ac3d99..2f64abce781f 100644
--- a/include/uapi/linux/virtio_fs.h
+++ b/include/uapi/linux/virtio_fs.h
@@ -16,4 +16,7 @@ struct virtio_fs_config {
__u32 num_request_queues;
} __attribute__((packed));
+/* For the id field in virtio_pci_shm_cap */
+#define VIRTIO_FS_SHMCAP_ID_CACHE 0
+
#endif /* _UAPI_LINUX_VIRTIO_FS_H */
--
2.20.1
