[dm-devel] dm-cache invalidate_cblocks range parsing
Joe Thornber
thornber at redhat.com
Mon Nov 25 10:00:02 UTC 2013
On Mon, Nov 25, 2013 at 09:50:19AM +0000, Joe Thornber wrote:
> On Sun, Nov 24, 2013 at 02:25:33AM +0000, Mears, Morgan wrote:
> > If one specifies a cblock range in the dm-cache invalidate_cblocks message
> > (commit 65790ff919e2e07ccb4457415c11075b245d643b), the final cblock in the
> > range does not get invalidated. For example, after:
> >
> > dmsetup message cache 0 invalidate_cblocks 10-11
> >
> > cblock 11 will still be in the cache. The reason is the (begin != end)
> > check in process_invalidation_request() (dm-cache-target.c); were it to
> > change to (begin <= end), the final block would be treated like the rest.
> >
> > However, parse_cblock_range() relies on the current behavior for the single
> > block case; if the change above were applied, an extra block would be
> > invalidated for each single-block invalidation request.
> >
> > So: is the current behavior intentional?
>
> Yes.
Documented in code, but I think Documentation/device-mapper/cache.txt should also say this.
/*
* Defines a range of cblocks, begin to (end - 1) are in the range. end is
* the one-past-the-end value.
*/
See
https://github.com/jthornber/device-mapper-test-suite/blob/master/lib/dmtest/tests/cache/invalidate_cblocks_tests.rb
for example uses.
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