[Qemu-devel] [PATCH 1/2] block: fix BDRV_O_SNAPSHOT protocol detection

[Stefan Hajnoczi <stefanha@redhat.com>]

realpath(3) is used to get an absolute path to the image file when
creating a -drive snapshot=on temporary qcow2.  This does not work for
protocols since their filenames ("proto:foo:...") do not correspond to
file system paths.

Commit 7c96d46ec245d73fd76726588409f9abe4bd5dc1 ("Let snapshot work with
protocols") skipped realpath(3) for protocols.  Later on the "raw"
format was introduced and broke the check.

Use path_has_protocol(filename) to decide if this image uses a protocol
or a filename.

Reported-by: Richard Jones <rjones@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index 124a9eb..acc7d1c 100644
--- a/block.c
+++ b/block.c
@@ -812,7 +812,6 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
     if (flags & BDRV_O_SNAPSHOT) {
         BlockDriverState *bs1;
         int64_t total_size;
-        int is_protocol = 0;
         BlockDriver *bdrv_qcow2;
         QEMUOptionParameter *options;
         char backing_filename[PATH_MAX];
@@ -829,9 +828,6 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         }
         total_size = bdrv_getlength(bs1) & BDRV_SECTOR_MASK;
 
-        if (bs1->drv && bs1->drv->protocol_name)
-            is_protocol = 1;
-
         bdrv_delete(bs1);
 
         ret = get_tmp_filename(tmp_filename, sizeof(tmp_filename));
@@ -840,11 +836,12 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         }
 
         /* Real path is meaningless for protocols */
-        if (is_protocol)
+        if (path_has_protocol(filename)) {
             snprintf(backing_filename, sizeof(backing_filename),
                      "%s", filename);
-        else if (!realpath(filename, backing_filename))
+        } else if (!realpath(filename, backing_filename)) {
             return -errno;
+        }
 
         bdrv_qcow2 = bdrv_find_format("qcow2");
         options = parse_option_parameters("", bdrv_qcow2->create_options, NULL);
-- 
1.8.1.4