On 07/01/2025 17:13, Mikulas Patocka wrote:
On Mon, 6 Jan 2025, John Garry wrote:
On 06/01/2025 17:26, Mike Snitzer wrote:
On Mon, Jan 06, 2025 at 12:41:14PM +0000, John Garry wrote:
This series introduces initial device mapper atomic write support.
Since we already support stacking atomic writes limits, it's quite
straightforward to support.
Only dm-linear is supported for now, but other personalities could
be supported.
Patch #1 is a proper fix, but the rest of the series is RFC - this is
because I have not fully tested and we are close to the end of this
development cycle.
In general, looks reasonable. But I would prefer to see atomic write
support added to dm-striped as well. Not that I have some need, but
because it will help verify the correctness of the general stacking
code changes (in both block and DM core).
That should be fine. We already have md raid0 support working (for atomic
writes), so I would expect much of the required support is already available.
BTW. could it be possible to add dm-mirror support as well? dm-mirror is
used when the user moves the logical volume to another physical volume, so
it would be nice if this worked without resulting in not-supported errors.
dm-mirror uses dm-io to perform the writes on multiple mirror legs (see
the function do_write() -> dm_io()), I looked at the code and it seems
that the support for atomic writes in dm-mirror and dm-io would be
straightforward.
I tried this out, and it seems to work ok.
However, I need to set DM_TARGET_ATOMIC_WRITES in the
mirror_target.features member, like:
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 9511dae5b556..913a92c55904 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -1485,6 +1485,7 @@ static struct target_type mirror_target = {
.name = "mirror",
.version = {1, 14, 0},
.module = THIS_MODULE,
+ .features = DM_TARGET_ATOMIC_WRITES,
.ctr = mirror_ctr,
.dtr = mirror_dtr,
.map = mirror_map,
Is this the right thing to do? I ask, as none of the other DM_TARGET*
flags are set already, which makes me suspicious.
Thanks,
John
