Hi,
--On 28 May 2007 12:45:59 PM +1000 David Chinner <dgc@sgi.com> wrote:
I would assume so.
Then when the block layer finds that they aren't supported and does
non-barrier ones, then it could report a message.
We, xfs, I guess can't take much other course of action
and we aint doing much now other than not requesting them
anymore and printing an error message.
Yep, and that one is what we want the FUA for -
for the write into the log.
I'm taking it that the FUA write will just guarantee that that
particular write has made it to disk on i/o completion
(and no write cache flush is done).
The other XFS constraint is that we know when the metadata hits the disk
so that we can move the tail of the log.
And that is what we are effectively getting from the pre-write-flush
part of the barrier. It would ensure that any metadata not yet to disk would
be on disk before we overwrite the tail of the log.
If we could determine cases when we don't have to worry about overwriting
the tail of the log, then it would be good if we could
just do FUA writes for contraint 1 above. Is that possible?
--Tim
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