lkml.org 
[lkml]   [2022]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v3 1/2] fscache,cachefiles: add prepare_ondemand_read() callback
From


On 11/16/22 9:41 PM, David Howells wrote:
> 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.

Okay.


>
>> 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.

I would prefer letting cachefiles_prepare_ondemand_read() pass flags in
and then tail call cachefiles_do_prepare_read() directly.

Many thanks for the suggestion.


--
Thanks,
Jingbo

\
 
 \ /
  Last update: 2022-11-17 05:25    [W:0.051 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site