linux-ext4 - [PATCH 06/74] tune2fs: forbid changing uuid on an uninit

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Message-ID: <20131211011857.30655.20986.stgit@birch.djwong.org>
Date:	Tue, 10 Dec 2013 17:18:57 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu, darrick.wong@...cle.com
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 06/74] tune2fs: forbid changing uuid on an uninit_bg filesystem

The old uninit_bg checksums depend on the UUID, so prohibit changes to
the UUID if a checksumming filesystem is mounted, because this
introduces a nasty race where the kernel and tune2fs are both trying
to rewrite group descriptors at the same time, with different ideas
about what the UUID is.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 misc/tune2fs.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/misc/tune2fs.c b/misc/tune2fs.c
index 1ae0ee6..111a43d 100644
--- a/misc/tune2fs.c
+++ b/misc/tune2fs.c
@@ -2653,8 +2653,7 @@ retry_open:
 		int set_csum = 0;
 		dgrp_t i;

-		if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
-				EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
+		if (ext2fs_has_group_desc_csum(fs)) {
 			/*
 			 * Changing the UUID requires rewriting all metadata,
 			 * which can race with a mounted fs.  Don't allow that.

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