linux-ext4 - [PATCH 40/54] mke2fs: Warn if not enabling all the features that metadata

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Message-ID: <20120307000207.11945.9180.stgit@elm3b70.beaverton.ibm.com>
Date:	Tue, 06 Mar 2012 16:02:07 -0800
From:	"Darrick J. Wong" <djwong@...ibm.com>
To:	Andreas Dilger <adilger.kernel@...ger.ca>,
	Theodore Tso <tytso@....edu>,
	"Darrick J. Wong" <djwong@...ibm.com>
Cc:	Sunil Mushran <sunil.mushran@...cle.com>,
	Amir Goldstein <amir73il@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Mingming Cao <cmm@...ibm.com>,
	Joel Becker <jlbec@...lplan.org>, linux-ext4@...r.kernel.org,
	Coly Li <colyli@...il.com>
Subject: [PATCH 40/54] mke2fs: Warn if not enabling all the features that
 metadata_csum wants

The metadata_csum feature works best when two features are enabled.  These
features are "extents" (because the block map has no space for checksums) and
"64bit" (this enables storage of full 32-bit checksums in certain fields).
Print a warning if the user tries to create a filesystem without those
features.

Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
---
 misc/mke2fs.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)


diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 61b332a..e8c60ca 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2309,6 +2309,25 @@ int main (int argc, char *argv[])
 		exit(1);
 	}
 
+	/* Check the user's mkfs options for metadata checksumming */
+	if (!quiet &&
+	    EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				       EXT4_FEATURE_RO_COMPAT_METADATA_CSUM)) {
+		if (!EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT3_FEATURE_INCOMPAT_EXTENTS))
+			printf(_("Extents are not enabled.  The file extent "
+				 "tree can be checksummed, whereas block maps "
+				 "cannot.  Not enabling extents reduces the "
+				 "coverage of metadata checksumming.  "
+				 "Pass -O extents to rectify.\n"));
+		if (!EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_INCOMPAT_64BIT))
+			printf(_("64-bit filesystem support is not "
+				 "enabled.  The larger fields afforded by "
+				 "this feature enable full-strength "
+				 "checksumming.  Pass -O 64bit to rectify.\n"));
+	}
+
 	/* Can't undo discard ... */
 	if (!noaction && discard && (io_ptr != undo_io_manager)) {
 		retval = mke2fs_discard_device(fs);

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