Re: [PATCH 18/52] virtio-fs: Map cache using the values from the capabilities

Liu Bo
2019-03-17T00:33:25Z

On Mon, Dec 10, 2018 at 9:57 AM Vivek Goyal <vgoyal@redhat.com> wrote:
>
> Instead of assuming we had the fixed bar for the cache, use the
> value from the capabilities.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
> fs/fuse/virtio_fs.c | 32 +++++++++++++++++---------------
> 1 file changed, 17 insertions(+), 15 deletions(-)
>
> diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> index 60d496c16841..55bac1465536 100644
> --- a/fs/fuse/virtio_fs.c
> +++ b/fs/fuse/virtio_fs.c
> @@ -14,11 +14,6 @@
> #include <uapi/linux/virtio_pci.h>
> #include "fuse_i.h"
>
> -enum {
> - /* PCI BAR number of the virtio-fs DAX window */
> - VIRTIO_FS_WINDOW_BAR = 2,
> -};
> -
> /* List of virtio-fs device instances and a lock for the list */
> static DEFINE_MUTEX(virtio_fs_mutex);
> static LIST_HEAD(virtio_fs_instances);
> @@ -518,7 +513,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> struct dev_pagemap *pgmap;
> struct pci_dev *pci_dev;
> phys_addr_t phys_addr;
> - size_t len;
> + size_t bar_len;
> int ret;
> u8 have_cache, cache_bar;
> u64 cache_offset, cache_len;
> @@ -551,17 +546,13 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> }
>
> /* TODO handle case where device doesn't expose BAR? */
> - ret = pci_request_region(pci_dev, VIRTIO_FS_WINDOW_BAR,
> - "virtio-fs-window");
> + ret = pci_request_region(pci_dev, cache_bar, "virtio-fs-window");
> if (ret < 0) {
> dev_err(&vdev->dev, "%s: failed to request window BAR\n",
> __func__);
> return ret;
> }
>
> - phys_addr = pci_resource_start(pci_dev, VIRTIO_FS_WINDOW_BAR);
> - len = pci_resource_len(pci_dev, VIRTIO_FS_WINDOW_BAR);
> -
> mi = devm_kzalloc(&pci_dev->dev, sizeof(*mi), GFP_KERNEL);
> if (!mi)
> return -ENOMEM;
> @@ -586,6 +577,17 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> pgmap->ref = &mi->ref;
> pgmap->type = MEMORY_DEVICE_FS_DAX;
>
> + phys_addr = pci_resource_start(pci_dev, cache_bar);
> + bar_len = pci_resource_len(pci_dev, cache_bar);
> +
> + if (cache_offset + cache_len > bar_len) {
> + dev_err(&vdev->dev,
> + "%s: cache bar shorter than cap offset+len\n",
> + __func__);
> + return -EINVAL;
> + }
> + phys_addr += cache_offset;
> +
> /* 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
> @@ -594,7 +596,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> pgmap->res = (struct resource){
> .name = "virtio-fs dax window",
> .start = phys_addr,
> - .end = phys_addr + len,
> + .end = phys_addr + cache_len,

Just in case you haven't noticed/fixed this problem, it should be

+ .end = phys_addr + cache_len - 1,

because resource_size() counts %size as "end - start + 1".
The end result of the above is a "conflicting page map" warning when
specifying a second virtio-fs pci device.

I'll send a patch for this, and feel free to take it along with the
patchset if needed.

thanks,
liubo

> };
>
> fs->window_kaddr = devm_memremap_pages(&pci_dev->dev, pgmap);
> @@ -607,10 +609,10 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
> return ret;
>
> fs->window_phys_addr = phys_addr;
> - fs->window_len = len;
> + fs->window_len = cache_len;
>
> - dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len %zu\n",
> - __func__, fs->window_kaddr, phys_addr, len);
> + dev_dbg(&vdev->dev, "%s: cache kaddr 0x%px phys_addr 0x%llx len %llx\n",
> + __func__, fs->window_kaddr, phys_addr, cache_len);
>
> fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops);
> if (!fs->dax_dev)
> --
> 2.13.6
>