Re: [PATCH v2] fuse: use newer inode info when writeback cache is enabled

[Fengnan Chang <changfengnan@vivo.com>]

Unh, it seems i_writecount not work.
If we modify file through lowerfs, i_writecount won't change, but the 
size already changed.
For example:
echo "111" > /lowerfs/test
ls -l /upper/test
echo "2222" >> /lowerfs/test
ls -l /upper/test

So, can you describe your test enviroment? including kernel version and 
fsx parameters, I will check it.

Thanks.

On 2021/6/22 15:59, Miklos Szeredi wrote:
> On Sat, 30 Jan 2021 at 09:50, Fengnan Chang <changfengnan@vivo.com> wrote:
>>
>> When writeback cache is enabled, the inode information in cached is
>> considered new by default, and the inode information of lowerfs is
>> stale.
>> When a lower fs is mount in a different directory through different
>> connection, for example PATHA and PATHB, since writeback cache is
>> enabled by default, when the file is modified through PATHA, viewing the
>> same file from the PATHB, PATHB will think that cached inode is newer
>> than lowerfs, resulting in file size and time from under PATHA and PATHB
>> is inconsistent.
>> Add a judgment condition to check whether to use the info in the cache
>> according to mtime.
> 
> This seems to break the fsx-linux stress test.
> 
> I suspect a better direction would be looking at whether the inode has
> any files open for write (i_writecount > 0)...
> 
> Thanks,
> Miklos
>