linux-kernel - Re: [PATCH v5 0/3] FUSE: Implement atomic lookup + open/create

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Date:   Thu, 1 Jun 2023 11:16:52 +0000
From:   Bernd Schubert <bschubert@....com>
To:     Miklos Szeredi <miklos@...redi.hu>,
        Dharmendra Singh <dharamhans87@...il.com>
CC:     Vivek Goyal <vgoyal@...hat.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        fuse-devel <fuse-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Horst Birthelmer <horst@...thelmer.com>
Subject: Re: [PATCH v5 0/3] FUSE: Implement atomic lookup + open/create

Hi Miklos,

On 5/19/22 11:39, Miklos Szeredi wrote:
> On Tue, 17 May 2022 at 12:08, Dharmendra Singh <dharamhans87@...il.com> wrote:
>>
>> In FUSE, as of now, uncached lookups are expensive over the wire.
>> E.g additional latencies and stressing (meta data) servers from
>> thousands of clients. These lookup calls possibly can be avoided
>> in some cases. Incoming three patches address this issue.
>>
>>
>> Fist patch handles the case where we are creating a file with O_CREAT.
>> Before we go for file creation, we do a lookup on the file which is most
>> likely non-existent. After this lookup is done, we again go into libfuse
>> to create file. Such lookups where file is most likely non-existent, can
>> be avoided.
> 
> I'd really like to see a bit wider picture...
> 
> We have several cases, first of all let's look at plain O_CREAT
> without O_EXCL (assume that there were no changes since the last
> lookup for simplicity):
> 
> [not cached, negative]
>     ->atomic_open()
>        LOOKUP
>        CREATE
> 

[...]

> [not cached]
>     ->atomic_open()
>         OPEN_ATOMIC

new patch version is eventually going through xfstests (and it finds 
some issues), but I have a question about wording here. Why 
"OPEN_ATOMIC" and not "ATOMIC_OPEN". Based on your comment  @Dharmendra 
renamed all functions and this fuse op "open atomic" instead of "atomic 
open" - for my non native English this sounds rather weird. At best it 
should be "open atomically"?


Thanks,
Bernd