On Sun, Apr 26, 2020 at 9:43 PM <tu...@posteo.de> wrote: > > To implement a dry run with a printf() is new to me... ;) >
That is all they fstrim authors could do, since there is no dry-run option for the actual ioctl, and fstrim itself has no idea how the filesystem will implement it (short of re-implementing numerous filesystems in the program and running it on unmounted devices). It seems like an fstrim dry-run is only minimally functional, though I guess it will test if you made any gross errors in syntax and so on. I don't see any reason why they couldn't have a dry-run option for the ioctl, but it would have to be implemented in the various filesystems. Really it seems like ioctl in general in the kernel isn't super-well-documented. It isn't like the system call interface. That is, unless I just missed some ioctl document floating around. The actual list of ioctls is in the kernel includes, but this does not define the syntax of the 3rd parameter of the ioctl system call which is function-specific. The structure used by the FITRIM ioctl is in the includes, but not with any kind of documentation or even a cross-reference to associate the structure with the ioctl itself. -- Rich
