[Xen-devel] [PATCH v6] libxl: allow 'phy' backend to use empty files

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

This was introduced by 97ee1f (~5 years ago), but was probably never
surfaced because most people used regular files as CDROM images, so the PHY
backend was actually never selected. A year ago this was changed, and now
regular RAW files are also handled by the PHY backend, which has made this
bug surface.

Fix it by allowing empty disks to use the PHY backend, skipping the stat
tests.

Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
Reported-by: Alex Braunegg <alex.braunegg@xxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Alex Braunegg <alex.braunegg@xxxxxxxxx>
---
Changes since v4:
 - Split form the rest of the series.
 - Fix disk_try_backend.
---
 tools/libxl/libxl_device.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index 8bb5e93..2e08108 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -196,6 +196,14 @@ static int disk_try_backend(disk_try_backend_args *a,
             goto bad_format;
         }
 
+        if (a->disk->format == LIBXL_DISK_FORMAT_EMPTY) {
+            assert(a->disk->pdev_path == NULL ||
+                   !strcmp(a->disk->pdev_path, ""));
+            LOG(DEBUG, "Disk vdev=%s is empty, skipping physical device check",
+                a->disk->vdev);
+            return backend;
+        }
+
         if (a->disk->backend_domid != LIBXL_TOOLSTACK_DOMID) {
             LOG(DEBUG, "Disk vdev=%s, is using a storage driver domain, "
                        "skipping physical device check", a->disk->vdev);
-- 
2.5.4 (Apple Git-61)


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