linux-kernel - Re: [PATCH 5/5] docs: fuse: improve FUSE consistency explanation

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Message-ID: <5a2d4d3f-9d9d-0ce9-c5a0-fb9bd64b9f48@bytedance.com>
Date:   Tue, 11 Jul 2023 15:15:29 +0800
From:   Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
To:     Randy Dunlap <rdunlap@...radead.org>,
        Miklos Szeredi <miklos@...redi.hu>,
        Jonathan Corbet <corbet@....net>,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     me@...x.top
Subject: Re: [PATCH 5/5] docs: fuse: improve FUSE consistency explanation


On 2023/7/11 12:42, Randy Dunlap wrote:
> Hi--
> 
> On 7/10/23 21:34, Jiachen Zhang wrote:
>> Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@...edance.com>
>> ---
>>   Documentation/filesystems/fuse-io.rst | 32 +++++++++++++++++++++++++--
>>   1 file changed, 30 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/filesystems/fuse-io.rst b/Documentation/filesystems/fuse-io.rst
>> index 255a368fe534..cdd292dd2e9c 100644
>> --- a/Documentation/filesystems/fuse-io.rst
>> +++ b/Documentation/filesystems/fuse-io.rst
> 
>> @@ -24,7 +31,8 @@ after any writes to the file.  All mmap modes are supported.
>>   The cached mode has two sub modes controlling how writes are handled.  The
>>   write-through mode is the default and is supported on all kernels.  The
>>   writeback-cache mode may be selected by the FUSE_WRITEBACK_CACHE flag in the
>> -FUSE_INIT reply.
>> +FUSE_INIT reply. In either modes, if the FOPEN_KEEP_CACHE flag is not set in
> 
>                         either mode,
> 
>> +the FUSE_OPEN, cached pages of the file will be invalidated immediatedly.
> 
>                                                                 immediately.
> 
>>   
>>   In write-through mode each write is immediately sent to userspace as one or more
>>   WRITE requests, as well as updating any cached pages (and caching previously
>> @@ -38,7 +46,27 @@ reclaim on memory pressure) or explicitly (invoked by close(2), fsync(2) and
>>   when the last ref to the file is being released on munmap(2)).  This mode
>>   assumes that all changes to the filesystem go through the FUSE kernel module
>>   (size and atime/ctime/mtime attributes are kept up-to-date by the kernel), so
>> -it's generally not suitable for network filesystems.  If a partial page is
>> +it's generally not suitable for network filesystems (you can consider the
>> +writeback-cache-v2 mode mentioned latter for them).  If a partial page is
> 
>                                       later
> 
>>   written, then the page needs to be first read from userspace.  This means, that
>>   even for files opened for O_WRONLY it is possible that READ requests will be
>>   generated by the kernel.
> 
> 


Thanks, Randy. I will fix them in the next version.

Jiachen