[Libguestfs] [PATCH 3/3] daemon: Run udev_settle after pwrite-device finishes.

[Jim Meyering]

Richard W.M. Jones wrote:

> From: "Richard W.M. Jones" <rjones at redhat.com>
>
> When you call close on any block device, udev kicks off a rule which
> runs blkid to reexamine the device.  We need to wait for this rule to
> finish running since it holds the device open and can cause other
> operations to fail, notably BLKRRPART.
> ---
>  daemon/file.c   |   17 ++++++++++++++---
>  daemon/parted.c |    3 ++-
>  2 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/daemon/file.c b/daemon/file.c
> index 91746e0..3e42c1e 100644
> --- a/daemon/file.c
> +++ b/daemon/file.c
> @@ -525,7 +525,7 @@ do_pread_device (const char *device, int count, int64_t offset, size_t *size_r)
>
>  static int
>  pwrite_fd (int fd, const char *content, size_t size, int64_t offset,
> -           const char *display_path)
> +           const char *display_path, int settle)
>  {
>    ssize_t r;
>
> @@ -541,6 +541,17 @@ pwrite_fd (int fd, const char *content, size_t size, int64_t offset,
>      return -1;
>    }
>
> +  /* When you call close on any block device, udev kicks off a rule
> +   * which runs blkid to reexamine the device.  We need to wait for
> +   * this rule to finish running since it holds the device open and
> +   * can cause other operations to fail, notably BLKRRPART.
> +   *
> +   * XXX We should be smarter about when we do this or should get rid
> +   * of the udev rules since we don't use blkid in cached mode.

This series looks fine.
Only question is what about non-block devices?

How about honoring "settle" only when fd is open on a block device?

  if (fstat (fd, &st) == 0 && S_ISBLK (st.st_mode) && settle)
    udev_settle ();

> +  if (settle)
> +    udev_settle ();
> +
>    return r;
>  }
>
> @@ -563,7 +574,7 @@ do_pwrite (const char *path, const char *content, size_t size, int64_t offset)
>      return -1;
>    }
>
> -  return pwrite_fd (fd, content, size, offset, path);
> +  return pwrite_fd (fd, content, size, offset, path, 0);
>  }
>
>  int
> @@ -581,7 +592,7 @@ do_pwrite_device (const char *device, const char *content, size_t size,
>      return -1;
>    }
>
> -  return pwrite_fd (fd, content, size, offset, device);
> +  return pwrite_fd (fd, content, size, offset, device, 1);
>  }
...