On Mon, Aug 10, 2020 at 11:48 AM David Howells <dhowells@xxxxxxxxxx> wrote: > > Steve French <smfrench@xxxxxxxxx> wrote: > > > cifs.ko also can set rsize quite small (even 1K for example, although > > that will be more than 10x slower than the default 4MB so hopefully no > > one is crazy enough to do that). > > You can set rsize < PAGE_SIZE? > > > I can't imagine an SMB3 server negotiating an rsize or wsize smaller than > > 64K in today's world (and typical is 1MB to 8MB) but the user can specify a > > much smaller rsize on mount. If 64K is an adequate minimum, we could change > > the cifs mount option parsing to require a certain minimum rsize if fscache > > is selected. > > I've borrowed the 256K granule size used by various AFS implementations for > the moment. A 512-byte xattr can thus hold a bitmap covering 1G of file > space. > > Is it possible to make the granule size configurable, then reject a registration if the size is too small or not a power of 2? Then a netfs using the API could try to set equal to rsize, and then error out with a message if the registration was rejected.
