Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH v3 1/2] fscache,cachefiles: add prepare_ondemand_read() callback | Date | Wed, 16 Nov 2022 13:41:41 +0000 |
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Jeff Layton <jlayton@kernel.org> wrote:
> > +static enum netfs_io_source cachefiles_do_prepare_read(struct netfs_cache_resources *cres, > > + loff_t *_start, size_t *_len, > > + unsigned long *_flags, loff_t i_size) > > _start is never changed, so it should be passed by value instead of by > pointer.
Hmmm. The intention was that the start pointer should be able to be moved backwards by the cache - but that's not necessary in ->prepare_read() and ->expand_readahead() is provided for that now. So yes, the start pointer shouldn't get changed at this point.
> I'd also reverse the position of the arguments for _flags and i_size. > Otherwise, the CPU/compiler have to shuffle things around more in > cachefiles_prepare_ondemand_read before they call this.
Better to pass the flags in and then ignore them. That way it can tail call, or just call cachefiles_do_prepare_read() directly from erofs. If you're going to have a wrapper, then you might be just as well create a netfs_io_subrequest struct on the stack.
David
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