From a3509912843852a2c3d7d5d0bc0e8a83c12ecea1 Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <a3at.mail@gmail.com>
Date: Thu, 19 May 2022 13:35:05 +0300
Subject: [PATCH] Disks: More accurate free space calculation for least_used

Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
---
 src/Disks/VolumeJBOD.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/Disks/VolumeJBOD.h b/src/Disks/VolumeJBOD.h
index 0fb80422d55..21d61e6dd8d 100644
--- a/src/Disks/VolumeJBOD.h
+++ b/src/Disks/VolumeJBOD.h
@@ -82,8 +82,9 @@ private:
         ReservationPtr reserve(uint64_t bytes)
         {
             ReservationPtr reservation = disk->reserve(bytes);
-            if (reservation)
-                free_size -= bytes;
+            /// Not just subtract bytes, but update the value,
+            /// since some reservations may be done directly via IDisk, or not by ClickHouse.
+            free_size = reservation->getUnreservedSpace();
             return reservation;
         }
     };