qga: Use error_setg_file_open() for better error messages

Error messages change from

    open("FNAME"): REASON

to

    Could not open 'FNAME': REASON

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
Reviewed-by: Kostiantyn Kostiuk <kkostiuk@redhat.com>
Message-ID: <20251121121438.1249498-6-armbru@redhat.com>

qga/commands-linux.c

@@ -1503,14 +1503,15 @@ static void transfer_vcpu(GuestLogicalProcessor *vcpu, bool sys2vcpu,
 
     dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
     if (dirfd == -1) {
-        error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
+        error_setg_file_open(errp, errno, dirpath);
         return;
     }
 
     fd = openat(dirfd, fn, sys2vcpu ? O_RDONLY : O_RDWR);
     if (fd == -1) {
         if (errno != ENOENT) {
-            error_setg_errno(errp, errno, "open(\"%s/%s\")", dirpath, fn);
+            error_setg_errno(errp, errno, "could not open %s/%s",
+                             dirpath, fn);
         } else if (sys2vcpu) {
             vcpu->online = true;
             vcpu->can_offline = false;
@@ -1712,7 +1713,7 @@ static void transfer_memory_block(GuestMemoryBlock *mem_blk, bool sys2memblk,
     dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
     if (dirfd == -1) {
         if (sys2memblk) {
-            error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
+            error_setg_file_open(errp, errno, dirpath);
         } else {
             if (errno == ENOENT) {
                 result->response = GUEST_MEMORY_BLOCK_RESPONSE_TYPE_NOT_FOUND;
@@ -1937,7 +1938,7 @@ static GuestDiskStatsInfoList *guest_get_diskstats(Error **errp)
 
     fp = fopen(diskstats, "r");
     if (fp  == NULL) {
-        error_setg_errno(errp, errno, "open(\"%s\")", diskstats);
+        error_setg_file_open(errp, errno, diskstats);
         return NULL;
     }
 
@@ -2048,7 +2049,7 @@ GuestCpuStatsList *qmp_guest_get_cpustats(Error **errp)
 
     fp = fopen(cpustats, "r");
     if (fp  == NULL) {
-        error_setg_errno(errp, errno, "open(\"%s\")", cpustats);
+        error_setg_file_open(errp, errno, cpustats);
         return NULL;
     }