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Re: [PATCH v3 18/26] DAX/unmap: virtiofsd: Add VHOST_USER_SLAVE_FS_IO
From: |
Stefan Hajnoczi |
Subject: |
Re: [PATCH v3 18/26] DAX/unmap: virtiofsd: Add VHOST_USER_SLAVE_FS_IO |
Date: |
Thu, 6 May 2021 16:12:07 +0100 |
On Wed, Apr 28, 2021 at 12:00:52PM +0100, Dr. David Alan Gilbert (git) wrote:
> @@ -220,6 +222,99 @@ uint64_t vhost_user_fs_slave_unmap(struct vhost_dev
> *dev, int message_size,
> return (uint64_t)res;
> }
>
> +uint64_t vhost_user_fs_slave_io(struct vhost_dev *dev, int message_size,
> + VhostUserFSSlaveMsg *sm, int fd)
> +{
> + VHostUserFS *fs = (VHostUserFS *)object_dynamic_cast(OBJECT(dev->vdev),
> + TYPE_VHOST_USER_FS);
> + if (!fs) {
> + error_report("%s: Bad fs ptr", __func__);
> + return (uint64_t)-1;
> + }
> + if (!check_slave_message_entries(sm, message_size)) {
> + return (uint64_t)-1;
> + }
These early error returns don't close(fd).
> +
> + unsigned int i;
> + int res = 0;
> + size_t done = 0;
> +
> + if (fd < 0) {
> + error_report("Bad fd for io");
> + return (uint64_t)-1;
> + }
> +
> + for (i = 0; i < sm->count && !res; i++) {
> + VhostUserFSSlaveMsgEntry *e = &sm->entries[i];
> + if (e->len == 0) {
> + continue;
> + }
> +
> + size_t len = e->len;
> + uint64_t fd_offset = e->fd_offset;
> + hwaddr gpa = e->c_offset;
> +
> + while (len && !res) {
> + hwaddr xlat, xlat_len;
> + bool is_write = e->flags & VHOST_USER_FS_FLAG_MAP_W;
> + MemoryRegion *mr = address_space_translate(dev->vdev->dma_as,
> gpa,
> + &xlat, &xlat_len,
> + is_write,
> +
> MEMTXATTRS_UNSPECIFIED);
> + if (!mr || !xlat_len) {
> + error_report("No guest region found for 0x%" HWADDR_PRIx,
> gpa);
> + res = -EFAULT;
> + break;
> + }
> +
> + trace_vhost_user_fs_slave_io_loop(mr->name,
> + (uint64_t)xlat,
> + memory_region_is_ram(mr),
> + memory_region_is_romd(mr),
> + (size_t)xlat_len);
> +
> + void *hostptr = qemu_map_ram_ptr(mr->ram_block,
> + xlat);
> + ssize_t transferred;
What happens when the MemoryRegion is not backed by RAM?
> + if (e->flags & VHOST_USER_FS_FLAG_MAP_R) {
> + /* Read from file into RAM */
> + if (mr->readonly) {
> + res = -EFAULT;
> + break;
> + }
> + transferred = pread(fd, hostptr, xlat_len, fd_offset);
> + } else if (e->flags & VHOST_USER_FS_FLAG_MAP_W) {
> + /* Write into file from RAM */
> + transferred = pwrite(fd, hostptr, xlat_len, fd_offset);
> + } else {
> + transferred = EINVAL;
I don't see how this is handled below by the error checking code. Should
this be:
errno = EINVAL;
transferred = -1;
?
> + }
> +
> + trace_vhost_user_fs_slave_io_loop_res(transferred);
> + if (transferred < 0) {
> + res = -errno;
> + break;
> + }
> + if (!transferred) {
> + /* EOF */
> + break;
> + }
> +
> + done += transferred;
> + fd_offset += transferred;
> + gpa += transferred;
> + len -= transferred;
> + }
> + }
> + close(fd);
> +
> + trace_vhost_user_fs_slave_io_exit(res, done);
> + if (res < 0) {
> + return (uint64_t)res;
> + }
> + return (uint64_t)done;
> +}
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- Re: [PATCH v3 18/26] DAX/unmap: virtiofsd: Add VHOST_USER_SLAVE_FS_IO,
Stefan Hajnoczi <=