[Devel] [PATCH vz10] dm-ploop: fix inverted nr_deltas check disabling construction-time prealloc

[Konstantin Khorenko]

The read-only guard added to ploop_ctr() also accidentally negated the
existing nr_deltas clause:

	-	if (ploop->nr_deltas > 0)
	+	if (!ploop_is_ro(ploop) && !(ploop->nr_deltas > 0))
			ploop_should_prealloc(ploop);

At this point ploop->nr_deltas is always >= 1 (ploop_add_deltas_stack()
just above returns -EINVAL for argc < 1 and otherwise sets nr_deltas =
argc, and ploop_ctr() rejects argc <= 0 earlier), so "nr_deltas > 0" is
always true and "!(nr_deltas > 0)" is always false. The whole condition
is therefore always false and ploop_should_prealloc() is never called -
for writable devices too, contrary to the commit's intent ("skip prealloc
for read-only, keep it for RW").

Drop the spurious inner negation so prealloc is enabled for RW devices
with deltas and skipped only for read-only ones. (Runtime allocation-path
prealloc was unaffected; this only restores eager construction-time
preallocation.)

Fixes: f268061806e5 ("dm-ploop: dont preallocate clusters for read only table")
https://virtuozzo.atlassian.net/browse/VSTOR-132310
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 drivers/md/dm-ploop-target.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index af0925712194..0de0e84d440d 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -635,7 +635,7 @@ static int ploop_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->num_discard_bios = 1;
 	ti->discards_supported = true;
 
-	if (!ploop_is_ro(ploop) && !(ploop->nr_deltas > 0))
+	if (!ploop_is_ro(ploop) && ploop->nr_deltas > 0)
 		ploop_should_prealloc(ploop);
 
 	return 0;
-- 
2.47.1