On 11/4/22 7:18 PM, Jeff Layton wrote:
> On Fri, 2022-11-04 at 15:26 +0800, Jingbo Xu wrote:
>> Add prepare_ondemand_read() callback dedicated for the on-demand read
>> scenario, so that callers from this scenario can be decoupled from
>> netfs_io_subrequest.
>>
>> To reuse the hole detecting logic as mush as possible, both the
>> implementation of prepare_read() and prepare_ondemand_read() inside
>> Cachefiles call a common routine.
>>
>> In the near future, prepare_read() will get enhanced and more
>> information will be needed and then returned to callers. Thus
>> netfs_io_subrequest is a reasonable candidate for holding places for all
>> these information needed in the internal implementation.
>>
>> Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
>> ---
>> fs/cachefiles/io.c | 42 +++++++++++++++++++++++++------
>> include/linux/netfs.h | 7 ++++++
>> include/trace/events/cachefiles.h | 4 +--
>> 3 files changed, 43 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
>> index 000a28f46e59..6427259fcba9 100644
>> --- a/fs/cachefiles/io.c
>> +++ b/fs/cachefiles/io.c
>> @@ -385,16 +385,11 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
>> term_func, term_func_priv);
>> }
>>
>> -/*
>> - * Prepare a read operation, shortening it to a cached/uncached
>> - * boundary as appropriate.
>> - */
>> -static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
>> - loff_t i_size)
>> +static enum netfs_io_source cachefiles_do_prepare_read(struct netfs_io_subrequest *subreq,
>> + struct netfs_cache_resources *cres,
>> + loff_t i_size)
>> {
>> enum cachefiles_prepare_read_trace why;
>> - struct netfs_io_request *rreq = subreq->rreq;
>> - struct netfs_cache_resources *cres = &rreq->cache_resources;
>> struct cachefiles_object *object;
>> struct cachefiles_cache *cache;
>> struct fscache_cookie *cookie = fscache_cres_cookie(cres);
>> @@ -501,6 +496,36 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
>> return ret;
>> }
>>
>> +/*
>> + * Prepare a read operation, shortening it to a cached/uncached
>> + * boundary as appropriate.
>> + */
>> +static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
>> + loff_t i_size)
>> +{
>> + return cachefiles_do_prepare_read(subreq,
>> + &subreq->rreq->cache_resources, i_size);
>> +}
>> +
>> +/*
>> + * Prepare an on-demand read operation, shortening it to a cached/uncached
>> + * boundary as appropriate.
>> + */
>> +static enum netfs_io_source cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
>> + loff_t start, size_t *_len, loff_t i_size)
>> +{
>> + enum netfs_io_source source;
>> + struct netfs_io_subrequest subreq = {
>> + .start = start,
>> + .len = *_len,
>> + .flags = 1 << NETFS_SREQ_ONDEMAND,
>> + };
>> +
>
> Faking up a struct like this is sort of fragile. What if we change
> cachefiles_do_prepare_read to consult other fields in this structure
> later?
Indeed it's not robust somehow.
>
> It might be best to have cachefiles_do_prepare_read take individual
> start, len, and flags values instead of doing this.
>
I will give it a try if nobody objects this.
Thank you for your suggestions :)
--
Thanks,
Jingbo
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