From 9d80fdcd63833c68d9b097765ebc2f0380bca98d Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Mon, 12 Aug 2019 13:48:51 +0200
Subject: [PATCH] qemu: snapshot: Restrict file existence check only for local
 storage
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Soon we'll allow more protocols and storage types with snapshots where
we in some cases can't check whether the storage already exists.
Restrict the sanity checks whether the destination images exist or not
for local storage where it's easy. For any other case we will fail
later.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/qemu/qemu_driver.c | 48 ++++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 23 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index ac235c9cc6..31202cf7f6 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15008,32 +15008,34 @@ qemuDomainSnapshotPrepareDiskExternal(virDomainDiskDefPtr disk,
             return -1;
     }
 
-    if (virStorageFileInit(snapdisk->src) < 0)
-        return -1;
-
-    rc = virStorageFileStat(snapdisk->src, &st);
-    err = errno;
-
-    virStorageFileDeinit(snapdisk->src);
-
-    if (rc < 0) {
-        if (err != ENOENT) {
-            virReportSystemError(err,
-                                 _("unable to stat for disk %s: %s"),
-                                 snapdisk->name, snapdisk->src->path);
+    if (virStorageSourceIsLocalStorage(snapdisk->src)) {
+        if (virStorageFileInit(snapdisk->src) < 0)
             return -1;
-        } else if (reuse) {
-            virReportSystemError(err,
-                                 _("missing existing file for disk %s: %s"),
-                                 snapdisk->name, snapdisk->src->path);
+
+        rc = virStorageFileStat(snapdisk->src, &st);
+        err = errno;
+
+        virStorageFileDeinit(snapdisk->src);
+
+        if (rc < 0) {
+            if (err != ENOENT) {
+                virReportSystemError(err,
+                                     _("unable to stat for disk %s: %s"),
+                                     snapdisk->name, snapdisk->src->path);
+                return -1;
+            } else if (reuse) {
+                virReportSystemError(err,
+                                     _("missing existing file for disk %s: %s"),
+                                     snapdisk->name, snapdisk->src->path);
+                return -1;
+            }
+        } else if (!S_ISBLK(st.st_mode) && st.st_size && !reuse) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("external snapshot file for disk %s already "
+                             "exists and is not a block device: %s"),
+                           snapdisk->name, snapdisk->src->path);
             return -1;
         }
-    } else if (!S_ISBLK(st.st_mode) && st.st_size && !reuse) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                       _("external snapshot file for disk %s already "
-                         "exists and is not a block device: %s"),
-                       snapdisk->name, snapdisk->src->path);
-        return -1;
     }
 
     return 0;