From b78d0e2856c5401d77839f95d9ae7d829abfa010 Mon Sep 17 00:00:00 2001
From: Akilesh Kailash <akailash@google.com>
Date: Wed, 29 Nov 2023 11:24:28 -0800
Subject: [PATCH] snapshotctl: fsync after writing every 1MB buffer

Sync writes after every 1MB instead of flushing at the end.

Bug: 299011882
Test: Boot device off snapshots
Change-Id: If91168ec92c2b2995bdf296ea1c7d4c261b12411
Signed-off-by: Akilesh Kailash <akailash@google.com>
---
 fs_mgr/libsnapshot/snapshotctl.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs_mgr/libsnapshot/snapshotctl.cpp b/fs_mgr/libsnapshot/snapshotctl.cpp
index ebaca2dbe..0396a55d6 100644
--- a/fs_mgr/libsnapshot/snapshotctl.cpp
+++ b/fs_mgr/libsnapshot/snapshotctl.cpp
@@ -227,8 +227,12 @@ bool MapSnapshots::WriteSnapshotPatch(std::string cow_device, std::string patch)
         if (file_offset >= dev_sz) {
             break;
         }
+
+        if (fsync(cfd.get()) < 0) {
+            PLOG(ERROR) << "Fsync failed at offset: " << file_offset << " size: " << to_read;
+            return false;
+        }
     }
-    fsync(cfd.get());
     return true;
 }