USB detection via getmntinfo kernel mount table

main.c

@@ -12,6 +12,7 @@
 #include <sys/sysctl.h>
 #include <sys/syscall.h>
 #include <sys/statvfs.h>
+#include <sys/mount.h>
 #include <time.h>
 #include <dirent.h>
 #include <ctype.h>
@@ -2248,12 +2249,11 @@ static void fn(struct mg_connection *c, int ev, void *ev_data) {
     }
     else if(mg_match(hm->uri,mg_str("/api/config/usb-status"),NULL)){
         char usb[32]={0}; int found=0;
-        struct stat mnt_st; stat("/mnt",&mnt_st);
-        for(int i=0;i<=7&&!found;i++){
-            char p[24]; snprintf(p,sizeof(p),"/mnt/usb%d",i);
-            struct stat st;
-            /* real mount: st_dev differs from parent /mnt */
-            if(stat(p,&st)==0&&st.st_dev!=mnt_st.st_dev){strncpy(usb,p,31);found=1;}
+        struct statfs *mntbuf; int n=getmntinfo(&mntbuf,MNT_NOWAIT);
+        for(int i=0;i<n&&!found;i++){
+            if(strncmp(mntbuf[i].f_mntonname,"/mnt/usb",8)==0){
+                strncpy(usb,mntbuf[i].f_mntonname,31);found=1;
+            }
         }
         mg_http_reply(c,200,"Content-Type: application/json\r\n",
             "{\"present\":%s,\"path\":\"%s\"}",found?"true":"false",found?usb:"");