4 ms·

Yep, that's called a "negative dentry".

• asveikau 4y ago
  But if a negative dentry does not yet exist, and a filename is requested for the first time, does it read from the fs? The DDoS scenario would be doing GET requests of random nonexistent filenames. You could change the name at every step so that the check for a negative dentry is never a cache hit.
  • vocram 4y ago
    If requesting http paths result in accessing the equivalent fs paths, then yes, you can dos it. But nowadays it’s uncommon for a webserver.
    • asveikau 4y ago
      Well the point under discussion is that i/o from a floppy disk is slow. Most servers have much faster disks and it'd be absurd to consider this. Also the page/buffer cache would probably cache the FAT direntries so probably not a huge issue here.