Re: [fuse-devel] [PATCH 1/2] [RFC for fuse-next ] fuse: DIO writes always use the same code path

[Hao Xu <hao.xu@linux.dev>]

On 8/22/23 17:53, Miklos Szeredi via fuse-devel wrote:
> On Mon, 21 Aug 2023 at 19:48, Bernd Schubert <bschubert@ddn.com> wrote:
>> There were two code paths direct-io writes could
>> take. When daemon/server side did not set FOPEN_DIRECT_IO
>>      fuse_cache_write_iter -> direct_write_fallback
>> and with FOPEN_DIRECT_IO being set
>>      fuse_direct_write_iter
>>
>> Advantage of fuse_direct_write_iter is that it has optimizations
>> for parallel DIO writes - it might only take a shared inode lock,
>> instead of the exclusive lock.
>>
>> With commits b5a2a3a0b776/80e4f25262f9 the fuse_direct_write_iter
>> path also handles concurrent page IO (dirty flush and page release),
>> just the condition on fc->direct_io_relax had to be removed.
>>
>> Performance wise this basically gives the same improvements as
>> commit 153524053bbb, just O_DIRECT is sufficient, without the need
>> that server side sets FOPEN_DIRECT_IO
>> (it has to set FOPEN_PARALLEL_DIRECT_WRITES), though.
> Consolidating the various direct IO paths would be really nice.
>
> Problem is that fuse_direct_write_iter() lacks some code from
> generic_file_direct_write() and also completely lacks


I see, seems the page invalidation post direct write is needed

as well.


> direct_write_fallback().   So more thought needs to go into this.
>
> Thanks,
> Miklos
>
>