Messages in this thread |  | | | Date | Mon, 23 Aug 2010 14:36:37 +0200 | | From | Tejun Heo <> | | Subject | Re: [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush |
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Hello,
On 08/20/2010 03:22 PM, Christoph Hellwig wrote: > Many storage devices, especially in the consumer market, come with volatile > write back caches. That means the devices signal I/O completion to the > operating system before data actually has hit the physical medium.
A bit nit picky but flash devices can also have writeback caches and the term physical medium sounds a bit off for those cases. Maybe just saying "non-volatile media" is better?
> Implementation details for filesystems > -------------------------------------- > > Filesystem can simply set the REQ_FLUSH and REQ_FUA bits and do not have to > worry if the underlying devices need any explicit cache flushing and how > the Forced Unit Access is implemented. The REQ_FLUSH and REQ_FUA flags > may both be set on a single bio.
It may be worthwhile to explain the sequence of operations when REQ_FLUSH + data + REQ_FUA is executed. It can be extrapolated from the previous two descriptions but I think giving examples of different sequences depending on FLUSH/FUA configuration would be helpful to help understanding the overall picture of things.
Other than those, looks good to me.
Thanks.
-- tejun
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