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Date:	Sat, 07 Jan 2012 00:36:59 -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 38/51] mke2fs: Warn if not enabling all the features that
	metadata_csum wants

There are some features (gdt_csum, 64bit, bg_use_meta_csum) that help
metadata_csum to work optimally.  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 |   35 ++++++++++++++++++++++++++++++++++-
 1 files changed, 34 insertions(+), 1 deletions(-)


diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 14c047a..80218bd 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -884,7 +884,8 @@ static __u32 ok_features[3] = {
 		EXT2_FEATURE_INCOMPAT_META_BG|
 		EXT4_FEATURE_INCOMPAT_FLEX_BG|
 		EXT4_FEATURE_INCOMPAT_MMP |
-		EXT4_FEATURE_INCOMPAT_64BIT,
+		EXT4_FEATURE_INCOMPAT_64BIT |
+		EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM,
 	/* R/O compat */
 	EXT2_FEATURE_RO_COMPAT_LARGE_FILE|
 		EXT4_FEATURE_RO_COMPAT_HUGE_FILE|
@@ -2298,6 +2299,38 @@ 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_RO_COMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_RO_COMPAT_GDT_CSUM))
+			printf(_("Group descriptor checksums "
+				 "are not enabled.  This reduces the "
+				 "coverage of metadata checksumming.  "
+				 "Pass -O uninit_bg to rectify.\n"));
+		if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_RO_COMPAT_GDT_CSUM) &&
+		    !EXT2_HAS_INCOMPAT_FEATURE(fs->super,
+				EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM))
+			printf(_("Group descriptor checksums will not use "
+				 "the faster metadata_checksum algorithm.  "
+				 "Pass -O bg_use_meta_csum to rectify.\n"));
+		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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