From 83aa54b4abb99f01fac329838bc64e62f0babe0e Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Sat, 11 Jul 2026 14:05:26 +0300
Subject: [PATCH] sys: FspFsvolWriteCached: move CcCanIWrite outside the locks

This eliminates the deadlock described in PR #677 while at the same time
ensuring that CcDeferWrite is called after the file's cache map has been
initialized.
---
 src/sys/write.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/sys/write.c b/src/sys/write.c
index 2ebe5074..e78fab70 100644
--- a/src/sys/write.c
+++ b/src/sys/write.c
@@ -247,8 +247,13 @@ static NTSTATUS FspFsvolWriteCached(
     FILE_END_OF_FILE_INFORMATION EndOfFileInformation;
     UINT64 WriteEndOffset;
     BOOLEAN ExtendingFile;
+    BOOLEAN DeferWrite;
     BOOLEAN Success;
 
+    /* should we defer the write? */
+    Success = DEBUGTEST(90) && CcCanIWrite(FileObject, WriteLength, CanWait, Retrying);
+    DeferWrite = !Success;
+
     /* try to acquire the FileNode Main exclusive */
     Success = DEBUGTEST(90) &&
         FspFileNodeTryAcquireExclusiveF(FileNode, FspFileNodeAcquireMain, CanWait);
@@ -306,8 +311,7 @@ static NTSTATUS FspFsvolWriteCached(
     }
 
     /* should we defer the write? */
-    Success = DEBUGTEST(90) && CcCanIWrite(FileObject, WriteLength, CanWait, Retrying);
-    if (!Success)
+    if (DeferWrite)
     {
         Result = FspWqCreateIrpWorkItem(Irp, FspFsvolWriteCached, 0);
         if (NT_SUCCESS(Result))