From 81e8155ff1c16dbf70206fbf239f99cf37c49432 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Tue, 31 Jan 2023 19:30:09 -0700
Subject: btrfsvol: Read: Avoid allocations for non-RAID reads

---
 lib/btrfs/btrfsvol/lvm.go | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

(limited to 'lib/btrfs/btrfsvol')

diff --git a/lib/btrfs/btrfsvol/lvm.go b/lib/btrfs/btrfsvol/lvm.go
index 93ec438..51e2263 100644
--- a/lib/btrfs/btrfsvol/lvm.go
+++ b/lib/btrfs/btrfsvol/lvm.go
@@ -345,21 +345,23 @@ func (lv *LogicalVolume[PhysicalVolume]) maybeShortReadAt(dat []byte, laddr Logi
 		dat = dat[:maxlen]
 	}
 
-	buf := make([]byte, len(dat))
+	buf := dat
 	first := true
 	for paddr := range paddrs {
 		dev, ok := lv.id2pv[paddr.Dev]
 		if !ok {
 			return 0, fmt.Errorf("device=%v does not exist", paddr.Dev)
 		}
+		if !first {
+			buf = make([]byte, len(buf))
+		}
 		if _, err := dev.ReadAt(buf, paddr.Addr); err != nil {
 			return 0, fmt.Errorf("read device=%v paddr=%v: %w", paddr.Dev, paddr.Addr, err)
 		}
-		if first {
-			copy(dat, buf)
-		} else if !bytes.Equal(dat, buf) {
+		if !first && !bytes.Equal(dat, buf) {
 			return 0, fmt.Errorf("inconsistent stripes at laddr=%v len=%v", laddr, len(dat))
 		}
+		first = false
 	}
 	return len(dat), nil
 }
-- 
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