On Tue, 17 Apr 2018, Mike Snitzer wrote: > On Mon, Apr 16 2018 at 6:33pm -0400, > Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > > > This patch adds a new class for dm-delay that delays flush requests. > > Previously, flushes were delayed as writes, but it caused problems if the > > user needed to create a device with one or few slow sectors for the > > purpose of testing - all flushes would be forwarded to this device and > > delayed, and that skews the test results. This patch allows to select 0 > > delay for flushes. > > > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > > The flush device shouldn't ever be allowed to be different than the > write device should it? Also, what does an offset even mean in the > context of flush? The flush device may be different if the user wants to suppress flushes (i.e. he could set the flush device to /dev/ram0, so that flushes are turned into nops). > Pretty awkward really. I get that you've factored out the ctr code and > are just reusing it for flush; and that in practice these knobs won't > get used (or flush_device won't be different than write_device).. but > I'm just not following why we want to expose flush_offset and > flush_device at all. > > Mike It's better to have the same arguments and same code paths for read/write/flush, then to invent new syntax just for flushes. Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
