rbd: add maxsnapshotsonimage flag

Added maxsnapshotsonimage flag to flatten
the older rbd images on the chain to avoid
issue in krbd.The limit is in krbd since it
only allocate 1 4KiB page to handle all the
snapshot ids for an image.

The max limit is 510 as per
https://github.com/torvalds/linux/blob/
aaa2faab4ed8e5fe0111e04d6e168c028fe2987f/drivers/block/rbd.c#L98
in cephcsi we arekeeping the default to 450 to reserve 10%
to avoid issues.
Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>

internal/rbd/driver.go

@@ -58,8 +58,8 @@ var (
 
 	// rbdSoftMaxCloneDepth is the soft limit for maximum number of nested volume clones that are taken before a flatten occurs
 	rbdSoftMaxCloneDepth uint
-
-	skipForceFlatten bool
+	maxSnapshotsOnImage  uint
+	skipForceFlatten     bool
 )
 
 // NewDriver returns new rbd driver
@@ -114,6 +114,7 @@ func (r *Driver) Run(conf *util.Config, cachePersister util.CachePersister) {
 	rbdHardMaxCloneDepth = conf.RbdHardMaxCloneDepth
 	rbdSoftMaxCloneDepth = conf.RbdSoftMaxCloneDepth
 	skipForceFlatten = conf.SkipForceFlatten
+	maxSnapshotsOnImage = conf.MaxSnapshotsOnImage
 	// Create instances of the volume and snapshot journal
 	volJournal = journal.NewCSIVolumeJournal(CSIInstanceID)
 	snapJournal = journal.NewCSISnapshotJournal(CSIInstanceID)

internal/util/util.go

@@ -108,6 +108,11 @@ type Config struct {
 
 	// RbdSoftMaxCloneDepth is the soft limit for maximum number of nested volume clones that are taken before a flatten occurs
 	RbdSoftMaxCloneDepth uint
+
+	// MaxSnapshotsOnImage represents the maximum number of snapshots allowed
+	// on rbd image without flattening, once the limit is reached cephcsi will
+	// start flattening the older rbd images to allow more snapshots
+	MaxSnapshotsOnImage uint
 }
 
 // CreatePersistanceStorage creates storage path and initializes new cache