fsdev: improve error handling of backend init

This patch changes some error messages in the backend init code and
convert backends to propagate QEMU Error objects instead of calling
error_report().

One notable improvement is that the local backend now provides a more
detailed error report when it fails to open the shared directory.

Signed-off-by: Greg Kurz <groug@kaod.org>

fsdev/file-op-9p.h

@@ -104,7 +104,7 @@ void cred_init(FsCred *);
 struct FileOperations
 {
     int (*parse_opts)(QemuOpts *, FsDriverEntry *, Error **errp);
-    int (*init)(FsContext *);
+    int (*init)(FsContext *, Error **errp);
     void (*cleanup)(FsContext *);
     int (*lstat)(FsContext *, V9fsPath *, struct stat *);
     ssize_t (*readlink)(FsContext *, V9fsPath *, char *, size_t);

hw/9pfs/9p-handle.c

@@ -604,7 +604,7 @@ static int handle_ioc_getversion(FsContext *ctx, V9fsPath *path,
 #endif
 }
 
-static int handle_init(FsContext *ctx)
+static int handle_init(FsContext *ctx, Error **errp)
 {
     int ret, mnt_id;
     struct statfs stbuf;

hw/9pfs/9p-local.c

@@ -1400,13 +1400,14 @@ static int local_ioc_getversion(FsContext *ctx, V9fsPath *path,
 #endif
 }
 
-static int local_init(FsContext *ctx)
+static int local_init(FsContext *ctx, Error **errp)
 {
     struct statfs stbuf;
     LocalData *data = g_malloc(sizeof(*data));
 
     data->mountfd = open(ctx->fs_root, O_DIRECTORY | O_RDONLY);
     if (data->mountfd == -1) {
+        error_setg_errno(errp, errno, "failed to open '%s'", ctx->fs_root);
         goto err;
     }
 

hw/9pfs/9p-proxy.c

@@ -1083,25 +1083,25 @@ static int proxy_ioc_getversion(FsContext *fs_ctx, V9fsPath *path,
     return err;
 }
 
-static int connect_namedsocket(const char *path)
+static int connect_namedsocket(const char *path, Error **errp)
 {
     int sockfd, size;
     struct sockaddr_un helper;
 
     if (strlen(path) >= sizeof(helper.sun_path)) {
-        error_report("Socket name too long");
+        error_setg(errp, "socket name too long");
         return -1;
     }
     sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
     if (sockfd < 0) {
-        error_report("Failed to create socket: %s", strerror(errno));
+        error_setg_errno(errp, errno, "failed to create client socket");
         return -1;
     }
     strcpy(helper.sun_path, path);
     helper.sun_family = AF_UNIX;
     size = strlen(helper.sun_path) + sizeof(helper.sun_family);
     if (connect(sockfd, (struct sockaddr *)&helper, size) < 0) {
-        error_report("Failed to connect to %s: %s", path, strerror(errno));
+        error_setg_errno(errp, errno, "failed to connect to '%s'", path);
         close(sockfd);
         return -1;
     }
@@ -1144,17 +1144,17 @@ static int proxy_parse_opts(QemuOpts *opts, FsDriverEntry *fs, Error **errp)
     return 0;
 }
 
-static int proxy_init(FsContext *ctx)
+static int proxy_init(FsContext *ctx, Error **errp)
 {
     V9fsProxy *proxy = g_malloc(sizeof(V9fsProxy));
     int sock_id;
 
     if (ctx->export_flags & V9FS_PROXY_SOCK_NAME) {
-        sock_id = connect_namedsocket(ctx->fs_root);
+        sock_id = connect_namedsocket(ctx->fs_root, errp);
     } else {
         sock_id = atoi(ctx->fs_root);
         if (sock_id < 0) {
-            error_report("Socket descriptor not initialized");
+            error_setg(errp, "socket descriptor not initialized");
         }
     }
     if (sock_id < 0) {

hw/9pfs/9p-synth.c

@@ -514,7 +514,7 @@ static int synth_unlinkat(FsContext *ctx, V9fsPath *dir,
     return -1;
 }
 
-static int synth_init(FsContext *ctx)
+static int synth_init(FsContext *ctx, Error **errp)
 {
     QLIST_INIT(&synth_root.child);
     qemu_mutex_init(&synth_mutex);

hw/9pfs/9p.c

@@ -3542,9 +3542,9 @@ int v9fs_device_realize_common(V9fsState *s, Error **errp)
     s->fid_list = NULL;
     qemu_co_rwlock_init(&s->rename_lock);
 
-    if (s->ops->init(&s->ctx) < 0) {
+    if (s->ops->init(&s->ctx, errp) < 0) {
-        error_setg(errp, "9pfs Failed to initialize fs-driver with id:%s"
+        error_prepend(errp, "cannot initialize fsdev '%s': ",
-                   " and export path:%s", s->fsconf.fsdev_id, s->ctx.fs_root);
+                      s->fsconf.fsdev_id);
         goto out;
     }