From: Chanyoung Park <chaney.p@kakaoenterprise.com>
Date: Fri, 15 Aug 2025 18:06:18 +0000 (+0000)
Subject: crimson/.../rbm_device: remove unnecessary zero fill in anonymous mmap
X-Git-Tag: v21.0.0~50^2~162^2~1
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=6f3229103e32c8c92c145921f863ba450d82d66f;p=ceph.git

crimson/.../rbm_device: remove unnecessary zero fill in anonymous mmap

Anonymous mmap is zero-filled on first access by the kernel, so an
explicit memset(0) is redundant and has been removed.

Signed-off-by: Chanyoung Park <chaney.p@kakaoenterprise.com>
---

diff --git a/src/crimson/os/seastore/random_block_manager/rbm_device.cc b/src/crimson/os/seastore/random_block_manager/rbm_device.cc
index bc592d12bcb..7cbd6ced39d 100644
--- a/src/crimson/os/seastore/random_block_manager/rbm_device.cc
+++ b/src/crimson/os/seastore/random_block_manager/rbm_device.cc
@@ -206,16 +206,12 @@ open_ertr::future<> EphemeralRBMDevice::open(
     "Initializing test memory device {}",
     size);
 
-  void* addr = ::mmap(
-    nullptr,
-    size,
-    PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS,
-    -1,
-    0);
+  // memset 0 is not needed: anonymous mapping is zero-filled
+  void* addr = ::mmap(nullptr, size, PROT_READ | PROT_WRITE,
+    MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
   buf = (char*)addr;
 
-  ::memset(buf, 0, size);
   return open_ertr::now();
 }