Re: [RFC PATCH 17/17] netfs: Combine prepare and issue ops and grab the buffers on request

[David Howells]

Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

> On Wed, Mar 04, 2026 at 02:03:24PM +0000, David Howells wrote:
> > +/*
> > + * Query the occupancy of the cache in a region, returning the extent of the
> > + * next chunk of cached data and the next hole.
> > + */
> > +static int cachefiles_query_occupancy(struct netfs_cache_resources *cres,
> > +				      struct fscache_occupancy *occ)
> > +{
> 
> Independent of fiemap or not, how is this supposed to work?  File
> systems can create speculative preallocations any time they want,
> so simply querying for holes vs data will corrupt your cache trivially.

SEEK_DATA and SEEK_HOLE avoid preallocations, I presume?

David