Re: when are buffers/caches flushed?

[Steven Scholz <steven.scholz@imc-berlin.de>]

Tejun,

>>>> How about recent kernels? Does sync() block until buffers are flushed?
>>>> How can I find out if the disk caches are actually flushed?
>>>>
>>>> I want to make sure that all data is flushed to my disk drive before 
>>>> powering down the system.
>>>
>>>  All disk caches are flushed before shutdown via the following path.
>>>
>>> kernel/sys.c::sys_reboot()
>>> kernel/drivers/base/power/shutdown.c::device_shutdown()
>>>  driver specific ->shutdown callback, for ide disks, the path is
>>> drivers/ide/ide-disk.c::ide_device_shutdown()
>>> drivers/ide/ide-disk.c::ide_cacheflush_p()
>>> drivers/ide/ide-disk.c::do_idedisk_flushcache()
>>>
>>>  And, AFAIK, sync() doesn't flush disk caches.
>>
>> How about umount?
>>
> 
> [CC'ing Bartlomiej (Hi!)]
> 
>  Hmmm, umount doesn't.  I think maybe adding cache flushing to sync and 
> umount can be helpful.

Ehm. So you're saying umount does _not_ flush the disk caches? BUT it will flush 
the the fs buffers, right?

>  And one more thing, ide-disk doesn't flush cache when shutting down. It 
> flushes only when rebooting.

How about ide-cs then? When I unregister a drive?

--
Steven