[PATCH v2 18/30] virtio_fs, dax: Set up virtio_fs dax_device

From: Vivek Goyal
Date: Wed May 15 2019 - 15:30:55 EST

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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/fuse_i.h | 1 +
fs/fuse/inode.c | 8 ++
fs/fuse/virtio_fs.c | 173 ++++++++++++++++++++++++++++++++-
include/uapi/linux/virtio_fs.h | 3 +
4 files changed, 183 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 46fc1a454084..840c88af711c 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -70,6 +70,7 @@ struct fuse_mount_data {
unsigned group_id_present:1;
unsigned default_permissions:1;
unsigned allow_other:1;
+ unsigned dax:1;
unsigned destroy:1;
unsigned max_read;
unsigned blksize;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 42f3ac5b7521..97d218a7daa8 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -442,6 +442,7 @@ enum {
OPT_ALLOW_OTHER,
OPT_MAX_READ,
OPT_BLKSIZE,
+ OPT_DAX,
OPT_ERR
};

@@ -455,6 +456,7 @@ static const match_table_t tokens = {
{OPT_ALLOW_OTHER, "allow_other"},
{OPT_MAX_READ, "max_read=%u"},
{OPT_BLKSIZE, "blksize=%u"},
+ {OPT_DAX, "dax"},
{OPT_ERR, NULL}
};

@@ -546,6 +548,10 @@ int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
d->blksize = value;
break;

+ case OPT_DAX:
+ d->dax = 1;
+ break;
+
default:
return 0;
}
@@ -574,6 +580,8 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root)
seq_printf(m, ",max_read=%u", fc->max_read);
if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
seq_printf(m, ",blksize=%lu", sb->s_blocksize);
+ if (fc->dax_dev)
+ seq_printf(m, ",dax");
return 0;
}

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index a23a1fb67217..2b790865dc21 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>
@@ -31,6 +34,18 @@ struct virtio_fs_vq {
char name[24];
} ____cacheline_aligned_in_smp;

+/* State needed for devm_memremap_pages(). This API is called on the
+ * underlying pci_dev instead of struct virtio_fs (layering violation). Since
+ * the memremap release function only gets called when the pci_dev is released,
+ * keep the associated state separate from struct virtio_fs (it has a different
+ * lifecycle from pci_dev).
+ */
+struct virtio_fs_memremap_info {
+ struct dev_pagemap pgmap;
+ struct percpu_ref ref;
+ struct completion completion;
+};
+
/* A virtio-fs device instance */
struct virtio_fs {
struct list_head list; /* on virtio_fs_instances */
@@ -38,6 +53,12 @@ struct virtio_fs {
struct virtio_fs_vq *vqs;
unsigned nvqs; /* number of virtqueues */
unsigned num_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 {
@@ -421,6 +442,151 @@ 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_percpu_release(struct percpu_ref *ref)
+{
+ struct virtio_fs_memremap_info *mi =
+ container_of(ref, struct virtio_fs_memremap_info, ref);
+
+ complete(&mi->completion);
+}
+
+static void virtio_fs_percpu_exit(void *data)
+{
+ struct virtio_fs_memremap_info *mi = data;
+
+ wait_for_completion(&mi->completion);
+ percpu_ref_exit(&mi->ref);
+}
+
+static void virtio_fs_percpu_kill(struct percpu_ref *ref)
+{
+ percpu_ref_kill(ref);
+}
+
+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 virtio_fs_memremap_info *mi;
+ struct dev_pagemap *pgmap;
+ bool have_cache;
+ int ret;
+
+ 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_err(&vdev->dev, "%s: No cache capability\n", __func__);
+ return -ENXIO;
+ } else {
+ dev_notice(&vdev->dev, "Cache len: 0x%llx @ 0x%llx\n",
+ cache_reg.len, cache_reg.addr);
+ }
+
+ mi = devm_kzalloc(&vdev->dev, sizeof(*mi), GFP_KERNEL);
+ if (!mi)
+ return -ENOMEM;
+
+ init_completion(&mi->completion);
+ ret = percpu_ref_init(&mi->ref, virtio_fs_percpu_release, 0,
+ GFP_KERNEL);
+ if (ret < 0) {
+ dev_err(&vdev->dev, "%s: percpu_ref_init failed (%d)\n",
+ __func__, ret);
+ return ret;
+ }
+
+ ret = devm_add_action(&vdev->dev, virtio_fs_percpu_exit, mi);
+ if (ret < 0) {
+ percpu_ref_exit(&mi->ref);
+ return ret;
+ }
+
+ pgmap = &mi->pgmap;
+ pgmap->altmap_valid = false;
+ pgmap->ref = &mi->ref;
+ pgmap->kill = virtio_fs_percpu_kill;
+ 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);
+ 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;
@@ -442,6 +608,10 @@ static int virtio_fs_probe(struct virtio_device *vdev)
/* TODO vq affinity */
/* TODO populate notifications vq */

+ 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.
*/
@@ -456,7 +626,6 @@ static int virtio_fs_probe(struct virtio_device *vdev)
out_vqs:
vdev->config->reset(vdev);
virtio_fs_cleanup_vqs(vdev, fs);
-
out:
vdev->priv = NULL;
return ret;
@@ -866,7 +1035,7 @@ static int virtio_fs_fill_super(struct super_block *sb, void *data,
goto err_free_fuse_devs;
__set_bit(FR_BACKGROUND, &init_req->flags);

- d.dax_dev = NULL;
+ d.dax_dev = d.dax ? fs->dax_dev : NULL;
d.fiq_ops = &virtio_fs_fiq_ops;
d.fiq_priv = fs;
d.fudptr = (void **)&fs->vqs[VQ_REQUEST].fud;
diff --git a/include/uapi/linux/virtio_fs.h b/include/uapi/linux/virtio_fs.h
index 48f3590dcfbe..d4bb549568eb 100644
--- a/include/uapi/linux/virtio_fs.h
+++ b/include/uapi/linux/virtio_fs.h
@@ -38,4 +38,7 @@ struct virtio_fs_config {
__u32 num_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

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Previous message: Vivek Goyal: "[PATCH v2 15/30] virtio: Implement get_shm_region for PCI transport"
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