[Qemu-block] [PATCH 16/19] block/nbd: Implement bdrv_dirname()

[Max Reitz]

The idea behind this implementation is that the export name might be
interpreted as a path (which is the only apparent interpretation of
relative filenames for NBD paths).

The default implementation of bdrv_dirname() would handle that just fine
for nbd+tcp, but not for nbd+unix, because in that case, the last
element of the path is the Unix socket path and not the export name.
Therefore, we need to implement an own bdrv_dirname() which uses the
legacy NBD URL which has the export name at the end.

Signed-off-by: Max Reitz <address@hidden>
---
 block/nbd.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/block/nbd.c b/block/nbd.c
index f7ea3b3..64534bb 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -469,6 +469,32 @@ static void nbd_refresh_filename(BlockDriverState *bs, 
QDict *options)
     bs->full_open_options = opts;
 }
 
+static char *nbd_dirname(BlockDriverState *bs, Error **errp)
+{
+    const char *path   = qdict_get_try_str(bs->options, "path");
+    const char *host   = qdict_get_try_str(bs->options, "host");
+    const char *port   = qdict_get_try_str(bs->options, "port");
+    const char *export = qdict_get_try_str(bs->options, "export");
+
+    if (path && export) {
+        return g_strdup_printf("nbd:unix:%s:exportname=%s/", path, export);
+    } else if (path && !export) {
+        return g_strdup_printf("nbd:unix:%s:exportname=", path);
+    } else if (!path && export && port) {
+        return g_strdup_printf("nbd://%s:%s/%s/", host, port, export);
+    } else if (!path && export && !port) {
+        return g_strdup_printf("nbd://%s/%s/", host, export);
+    } else if (!path && !export && port) {
+        return g_strdup_printf("nbd://%s:%s/", host, port);
+    } else if (!path && !export && !port) {
+        return g_strdup_printf("nbd://%s/", host);
+    }
+
+    error_setg(errp, "Cannot generate a base directory for NBD node '%s'",
+               bs->filename);
+    return NULL;
+}
+
 static BlockDriver bdrv_nbd = {
     .format_name                = "nbd",
     .protocol_name              = "nbd",
@@ -487,6 +513,7 @@ static BlockDriver bdrv_nbd = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_dirname               = nbd_dirname,
 };
 
 static BlockDriver bdrv_nbd_tcp = {
@@ -507,6 +534,7 @@ static BlockDriver bdrv_nbd_tcp = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_dirname               = nbd_dirname,
 };
 
 static BlockDriver bdrv_nbd_unix = {
@@ -527,6 +555,7 @@ static BlockDriver bdrv_nbd_unix = {
     .bdrv_detach_aio_context    = nbd_detach_aio_context,
     .bdrv_attach_aio_context    = nbd_attach_aio_context,
     .bdrv_refresh_filename      = nbd_refresh_filename,
+    .bdrv_dirname               = nbd_dirname,
 };
 
 static void bdrv_nbd_init(void)
-- 
2.8.0