From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 16 Sep 2025 20:25:06 +0000 (+0200)
Subject: vmspawn: initialize block device "serials" from backing file name
X-Git-Tag: v259-rc1~552^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b5ba882bd9ae4e0ed270289eada03c2040fefe2;p=thirdparty%2Fsystemd.git

vmspawn: initialize block device "serials" from backing file name

If we pass multiple block devices into a VM it's really useful to pass
recognizable serial numbers on them, so that we know which one is which.
qemu allows setting them, hence initialize them automatically from the
filename of the backing file, as a convenience feature.

Inside of a VM this means /dev/disk/by-id/… symlinks will be generated
with useful identifiers.
---

diff --git a/src/vmspawn/vmspawn.c b/src/vmspawn/vmspawn.c
index 544710d3107..8d3d168afe7 100644
--- a/src/vmspawn/vmspawn.c
+++ b/src/vmspawn/vmspawn.c
@@ -2094,24 +2094,30 @@ static int run_virtual_machine(int kvm_device_fd, int vhost_device_fd) {
         }
 
         if (arg_image) {
-                _cleanup_free_ char *escaped_image = NULL;
-
                 assert(!arg_directory);
 
-                r = strv_extend(&cmdline, "-drive");
-                if (r < 0)
+                if (strv_extend(&cmdline, "-drive") < 0)
                         return log_oom();
 
-                escaped_image = escape_qemu_value(arg_image);
+                _cleanup_free_ char *escaped_image = escape_qemu_value(arg_image);
                 if (!escaped_image)
                         return log_oom();
 
-                r = strv_extendf(&cmdline, "if=none,id=vmspawn,file=%s,format=raw,discard=%s", escaped_image, on_off(arg_discard_disk));
-                if (r < 0)
+                if (strv_extendf(&cmdline, "if=none,id=vmspawn,file=%s,format=raw,discard=%s", escaped_image, on_off(arg_discard_disk)) < 0)
                         return log_oom();
 
-                r = strv_extend_many(&cmdline, "-device", "virtio-blk-pci,drive=vmspawn,bootindex=1");
-                if (r < 0)
+                _cleanup_free_ char *image_fn = NULL;
+                if (path_extract_filename(arg_image, &image_fn) < 0)
+                        return log_error_errno(r, "Failed to extract filename from path '%s': %m", image_fn);
+
+                _cleanup_free_ char *escaped_image_fn = escape_qemu_value(image_fn);
+                if (!escaped_image_fn)
+                        return log_oom();
+
+                if (strv_extend(&cmdline, "-device") < 0)
+                        return log_oom();
+
+                if (strv_extendf(&cmdline, "virtio-blk-pci,drive=vmspawn,bootindex=1,serial=%s", escaped_image_fn) < 0)
                         return log_oom();
 
                 r = grow_image(arg_image, arg_grow_image);
@@ -2186,21 +2192,18 @@ static int run_virtual_machine(int kvm_device_fd, int vhost_device_fd) {
 
         size_t i = 0;
         STRV_FOREACH(drive, arg_extra_drives) {
-                _cleanup_free_ char *escaped_drive = NULL;
-                const char *driver = NULL;
-                struct stat st;
-
-                r = strv_extend(&cmdline, "-blockdev");
-                if (r < 0)
+                if (strv_extend(&cmdline, "-blockdev") < 0)
                         return log_oom();
 
-                escaped_drive = escape_qemu_value(*drive);
+                _cleanup_free_ char *escaped_drive = escape_qemu_value(*drive);
                 if (!escaped_drive)
                         return log_oom();
 
+                struct stat st;
                 if (stat(*drive, &st) < 0)
                         return log_error_errno(errno, "Failed to stat '%s': %m", *drive);
 
+                const char *driver = NULL;
                 if (S_ISREG(st.st_mode))
                         driver = "file";
                 else if (S_ISBLK(st.st_mode))
@@ -2208,16 +2211,22 @@ static int run_virtual_machine(int kvm_device_fd, int vhost_device_fd) {
                 else
                         return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Expected regular file or block device, not '%s'.", *drive);
 
-                r = strv_extendf(&cmdline, "driver=raw,cache.direct=off,cache.no-flush=on,file.driver=%s,file.filename=%s,node-name=vmspawn_extra_%zu", driver, escaped_drive, i);
-                if (r < 0)
+                if (strv_extendf(&cmdline, "driver=raw,cache.direct=off,cache.no-flush=on,file.driver=%s,file.filename=%s,node-name=vmspawn_extra_%zu", driver, escaped_drive, i) < 0)
                         return log_oom();
 
-                r = strv_extend(&cmdline, "-device");
+                _cleanup_free_ char *drive_fn = NULL;
+                r = path_extract_filename(*drive, &drive_fn);
                 if (r < 0)
+                        return log_error_errno(r, "Failed to extract filename from path '%s': %m", *drive);
+
+                _cleanup_free_ char *escaped_drive_fn = escape_qemu_value(drive_fn);
+                if (!escaped_drive_fn)
                         return log_oom();
 
-                r = strv_extendf(&cmdline, "scsi-hd,drive=vmspawn_extra_%zu", i++);
-                if (r < 0)
+                if (strv_extend(&cmdline, "-device") < 0)
+                        return log_oom();
+
+                if (strv_extendf(&cmdline, "scsi-hd,drive=vmspawn_extra_%zu,serial=%s", i++, escaped_drive_fn) < 0)
                         return log_oom();
         }