From 4337c7582c835720d18511deb8390774eb96ec60 Mon Sep 17 00:00:00 2001
From: Adrien Destugues <pulkomandy@pulkomandy.tk>
Date: Tue, 8 Oct 2019 19:56:39 +0200
Subject: [PATCH] btrfs: do not create Journal and ExtentAllocator for
 read-only

They are not needed, and the ExtentAllocator seems to currently fail on
an empty volume I created for testing.
---
 .../file_systems/btrfs/ExtentAllocator.cpp    |  6 ++--
 .../kernel/file_systems/btrfs/Volume.cpp      | 29 +++++++++++--------
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/src/add-ons/kernel/file_systems/btrfs/ExtentAllocator.cpp b/src/add-ons/kernel/file_systems/btrfs/ExtentAllocator.cpp
index a677700378..cbffe1af72 100644
--- a/src/add-ons/kernel/file_systems/btrfs/ExtentAllocator.cpp
+++ b/src/add-ons/kernel/file_systems/btrfs/ExtentAllocator.cpp
@@ -581,19 +581,19 @@ ExtentAllocator::Initialize()
 
 	status_t status = _LoadExtentTree(BTRFS_BLOCKGROUP_FLAG_DATA);
 	if (status != B_OK) {
-		ERROR("ExtentAllocator:: could not load exent tree (data)\n");
+		ERROR("ExtentAllocator:: could not load extent tree (data)\n");
 		return status;
 	}
 
 	status = _LoadExtentTree(BTRFS_BLOCKGROUP_FLAG_SYSTEM);
 	if (status != B_OK) {
-		ERROR("ExtentAllocator:: could not load exent tree (system)\n");
+		ERROR("ExtentAllocator:: could not load extent tree (system)\n");
 		return status;
 	}
 
 	status = _LoadExtentTree(BTRFS_BLOCKGROUP_FLAG_METADATA);
 	if (status != B_OK) {
-		ERROR("ExtentAllocator:: could not load exent tree (metadata)\n");
+		ERROR("ExtentAllocator:: could not load extent tree (metadata)\n");
 		return status;
 	}
 
diff --git a/src/add-ons/kernel/file_systems/btrfs/Volume.cpp b/src/add-ons/kernel/file_systems/btrfs/Volume.cpp
index c1bfbaf331..ff4f227bce 100644
--- a/src/add-ons/kernel/file_systems/btrfs/Volume.cpp
+++ b/src/add-ons/kernel/file_systems/btrfs/Volume.cpp
@@ -431,19 +431,24 @@ Volume::Mount(const char* deviceName, uint32 flags)
 	TRACE("Volume::Mount() Find larget inode id % " B_PRIu64 "\n",
 		fLargestInodeID);
 
-	// Initialize Journal
-	fJournal = new(std::nothrow) Journal(this);
-	if (fJournal == NULL)
-		return B_NO_MEMORY;
+	if ((flags & B_MOUNT_READ_ONLY) != 0) {
+		fJournal = NULL;
+		fExtentAllocator = NULL;
+	} else {
+		// Initialize Journal
+		fJournal = new(std::nothrow) Journal(this);
+		if (fJournal == NULL)
+			return B_NO_MEMORY;
 
-	// Initialize ExtentAllocator;
-	fExtentAllocator = new(std::nothrow) ExtentAllocator(this);
-	if (fExtentAllocator == NULL)
-		return B_NO_MEMORY;
-	status = fExtentAllocator->Initialize();
-	if (status != B_OK) {
-		ERROR("could not initalize extent allocator!\n");
-		return status;
+		// Initialize ExtentAllocator;
+		fExtentAllocator = new(std::nothrow) ExtentAllocator(this);
+		if (fExtentAllocator == NULL)
+			return B_NO_MEMORY;
+		status = fExtentAllocator->Initialize();
+		if (status != B_OK) {
+			ERROR("could not initalize extent allocator!\n");
+			return status;
+		}
 	}
 
 	// ready