Re: vfat vs msdos and -o flush

[Jeff Mahoney <jeffm@suse.com>]

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On 03/09/2010 08:42 AM, Chris Mason wrote:
> On Wed, Mar 03, 2010 at 10:36:21PM +0900, OGAWA Hirofumi wrote:
>> Christoph Hellwig <hch@lst.de> writes:
>>
>>> Commit ae78bf9c4f5fde3c67e2829505f195d7347ce3e4 added a -o flush
>>> option to the fat driver back in 2006, which causes asynchronous
>>> writeout after I/O operations ASAP.  This already is quite hacky
>>> and not something I like very much, but even worse the option
>>> is accepted when using the more common vfat filesysten type, but
>>> only actually implemented for the less common legacy msdos
>>> filesystem type.
>>>
>>> This tells us two lessons:
>>>
>>>   - the -o flush option probably never got a whole lot of exposure
>>>     and users didn't notice it doesn't work.  We might as well just
>>>     remove it again
>>
>> Sigh. Chris, could you handle this?
> 
> I'm not against removing it.  The option was added to handle desktop
> workloads where mount -o sync was too slow but people still wanted to be
> able to rip out the usb stick..  Added Jeff to the cc list, is this still
> in use?
> 
> Now that we have per-bdi dirty accounting, I think we're much much
> better off to set the dirty limit on the bdi to 1 byte or something and
> just let the page cache code do it all for us.

Yes, we still use it on openSUSE, but we haven't gotten any reports
about it being broken. I expect it's because it's only partly broken and
users haven't run into breakage with pure metadata operations. The inode
still gets written back when the file is closed.

If this can be solved differently, perfect.

- -Jeff

- -- 
Jeff Mahoney
SUSE Labs
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