From 654a6e98712f12ea12a0b6738568d15b44af746e Mon Sep 17 00:00:00 2001
From: Harshavardhana <harsha@minio.io>
Date: Tue, 17 Aug 2021 07:43:24 -0700
Subject: [PATCH] always set the filter to skip navigating baseDir (#12984)

baseDir is empty if the top level prefix does not
end with `/` this causes large recursive listings
without any filtering, to fix this filtering make
sure to set the filter prefix appropriately.

also do not navigate folders at top level that do
not match the filter prefix, entries don't need
to match prefix since they are never prefixed
with the prefix anyways.
---
 cmd/metacache-server-pool.go | 1 +
 cmd/metacache-walk.go        | 9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/cmd/metacache-server-pool.go b/cmd/metacache-server-pool.go
index c78a1e7f3..f034fa268 100644
--- a/cmd/metacache-server-pool.go
+++ b/cmd/metacache-server-pool.go
@@ -97,6 +97,7 @@ func (z *erasureServerPools) listPath(ctx context.Context, o *listPathOptions) (
 	o.parseMarker()
 	o.BaseDir = baseDirFromPrefix(o.Prefix)
 	o.Transient = o.Transient || isReservedOrInvalidBucket(o.Bucket, false)
+	o.SetFilter()
 	if o.Transient {
 		o.Create = false
 	}
diff --git a/cmd/metacache-walk.go b/cmd/metacache-walk.go
index 5825e3ed7..622f7a3e7 100644
--- a/cmd/metacache-walk.go
+++ b/cmd/metacache-walk.go
@@ -110,6 +110,11 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 	var scanDir func(path string) error
 
 	scanDir = func(current string) error {
+		// always skip the directory that doesn't match the prefix
+		if len(current) > 0 && !strings.HasPrefix(current, prefix) {
+			return nil
+		}
+
 		// Skip forward, if requested...
 		forward := ""
 		if len(opts.ForwardTo) > 0 && strings.HasPrefix(opts.ForwardTo, current) {
@@ -138,9 +143,6 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 		}
 		dirObjects := make(map[string]struct{})
 		for i, entry := range entries {
-			if len(prefix) > 0 && !strings.HasPrefix(entry, prefix) {
-				continue
-			}
 			if len(forward) > 0 && entry < forward {
 				continue
 			}
@@ -197,7 +199,6 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 		// Process in sort order.
 		sort.Strings(entries)
 		dirStack := make([]string, 0, 5)
-		prefix = "" // Remove prefix after first level.
 		if len(forward) > 0 {
 			idx := sort.SearchStrings(entries, forward)
 			if idx > 0 {