Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17]

On Tue, Mar 03, 2020 at 02:34:42PM +0100, Miklos Szeredi wrote:

On Tue, Mar 3, 2020 at 2:14 PM Greg Kroah-Hartman
[off-list ref] wrote:

quoted

quoted

Unlimited beers for a 21-line kernel patch?  Sign me up!

Totally untested, barely compiled patch below.

Ok, that didn't even build, let me try this for real now...

Some comments on the interface:

Ok, hey, let's do this proper :)

O_LARGEFILE can be unconditional, since offsets are not exposed to the caller.

Good point.

Use the openat2 style arguments; limit the accepted flags to sane ones
(e.g. don't let this syscall create a file).

Yeah, I just added that check to my local version:
	/* Mask off all O_ flags as we only want to read from the file */
	flags &= ~(VALID_OPEN_FLAGS);
	flags |= O_RDONLY | O_LARGEFILE;

If buffer is too small to fit the whole file, return error.

Why?  What's wrong with just returning the bytes asked for?  If someone
only wants 5 bytes from the front of a file, it should be fine to give
that to them, right?

Verify that the number of bytes read matches the file size, otherwise
return error (may need to loop?).

No, we can't "match file size" as sysfs files do not really have a sane
"size".  So I don't want to loop at all here, one-shot, that's all you
get :)

Let me actually do this and try it out for real.

/me has no idea what he is getting himself into...

thanks,

greg k-h