[Devel] [PATCH 2/2] dm-ploop: refactor dm target status callback

[Alexander Mikhalitsyn]

After 91ccbbac17 ("dm ima: measure data on table load") a new
STATUSTYPE_IMA was introduced.

For qcow2 it triggered compile time warning:
warning: drivers/md/dm-qcow2-target.c:897:9: warning: enumeration value ‘STATUSTYPE_IMA’ not handled in switch [-Wswitch]
but for dm-ploop is not. That's because we have no switch operator
in the status callback implementation there. That's not perfect,
it's better to have all status_type_t enum cases handled explicitly.

This patch changes behavior. Now for STATUSTYPE_INFO we always return
nothing, and for STATUSTYPE_TABLE we returing some data. This not breaks
anything because we have no usage of this ioctl(DM_IOCTL) in our userspace.

https://jira.sw.ru/browse/PSBM-140279

Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
---
 drivers/md/dm-ploop-target.c | 41 +++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/drivers/md/dm-ploop-target.c b/drivers/md/dm-ploop-target.c
index b4607d2bab65..d7cc2fbba537 100644
--- a/drivers/md/dm-ploop-target.c
+++ b/drivers/md/dm-ploop-target.c
@@ -452,22 +452,33 @@ static void ploop_status(struct dm_target *ti, status_type_t type,
 	char stat[32], *p = stat;
 	ssize_t sz = 0;
 
-	down_read(&ploop->ctl_rwsem);
-	if (ploop->falloc_new_clu)
-		*p++ = 'f';
-	if (READ_ONCE(ploop->noresume))
-		*p++ = 'n';
-	if (READ_ONCE(ploop->event_enospc))
-		*p++ = 's';
-	if (p == stat)
-		*p++ = 'o';
-	if (ploop->skip_off)
-		p += sprintf(p, " off=%llu", ploop->skip_off);
-	*p++ = '\0';
-	up_read(&ploop->ctl_rwsem);
+	switch (type) {
+	case STATUSTYPE_INFO:
+		result[0] = '\0';
+		break;
+	case STATUSTYPE_TABLE:
+		down_read(&ploop->ctl_rwsem);
+		if (ploop->falloc_new_clu)
+			*p++ = 'f';
+		if (READ_ONCE(ploop->noresume))
+			*p++ = 'n';
+		if (READ_ONCE(ploop->event_enospc))
+			*p++ = 's';
+		if (p == stat)
+			*p++ = 'o';
+		if (ploop->skip_off)
+			p += sprintf(p, " off=%llu", ploop->skip_off);
+		*p++ = '\0';
+		up_read(&ploop->ctl_rwsem);
+
+		BUG_ON(p - stat >= sizeof(stat));
+		DMEMIT("%u v2 %u %s", ploop->nr_deltas, (u32)CLU_TO_SEC(ploop, 1), stat);
 
-	BUG_ON(p - stat >= sizeof(stat));
-	DMEMIT("%u v2 %u %s", ploop->nr_deltas, (u32)CLU_TO_SEC(ploop, 1), stat);
+		break;
+	case STATUSTYPE_IMA:
+		result[0] = '\0';
+		break;
+	}
 }
 
 static void ploop_set_wants_suspend(struct dm_target *ti, bool wants)
-- 
2.36.1