Re: [PATCH 07/10] fs: make generic file read/write functions plug

[hch@xxxxxxxxxxxxx]

On Fri, Mar 04, 2011 at 02:22:21PM +0100, Jens Axboe wrote:
> Good catch, we need to modify that logic. If the task is currently
> plugged, it should not dispatch until blk_finish_plug() is called.
> Essentially SYNC will not control dispatch. Will allow us to clean up
> that logic, too.

<broken-record-mode>

Time to use the opportunity to sort out what the various bio/request
flags mean.

REQ_UNPLUG should simply go away with the explicit stack plugging.
What's left for REQ_SYNC?  It'll control if the request goes into the
sync bucket and some cfq tweaks.  We should clearly document what it
does.

REQ_META?  Maybe we should finally agree what it does and decide if it
should be used consistenly.  Especially the priority over REQ_SYNC in
cfq still looks somewhat odd, as does the totally inconsequent use.

</broken-record-mode>
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