linux-ext4 - [PATCH 04/54] libext2fs: Precompute FS UUID checksum seed

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Date:	Tue, 06 Mar 2012 15:57:47 -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 04/54] libext2fs: Precompute FS UUID checksum seed

Precompute the FS UUID checksum seed that is used for all metadata checksumming
operations and store it in ext2_filsys.

Signed-off-by: Darrick J. Wong <djwong@...ibm.com>
---
 e2fsck/super.c      |    1 +
 lib/ext2fs/ext2fs.h |   14 ++++++++++++++
 lib/ext2fs/openfs.c |    2 ++
 misc/mke2fs.c       |    1 +
 4 files changed, 18 insertions(+), 0 deletions(-)


diff --git a/e2fsck/super.c b/e2fsck/super.c
index 3397d77..94648c3 100644
--- a/e2fsck/super.c
+++ b/e2fsck/super.c
@@ -710,6 +710,7 @@ void check_super_block(e2fsck_t ctx)
 	if (!(ctx->options & E2F_OPT_READONLY) && uuid_is_null(sb->s_uuid)) {
 		if (fix_problem(ctx, PR_0_ADD_UUID, &pctx)) {
 			uuid_generate(sb->s_uuid);
+			ext2fs_init_csum_seed(fs);
 			fs->flags |= EXT2_FLAG_DIRTY;
 			fs->flags &= ~EXT2_FLAG_MASTER_SB_ONLY;
 		}
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index bde22b6..f7a73e5 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -281,6 +281,9 @@ struct struct_ext2_filsys {
 	 * Time at which e2fsck last updated the MMP block.
 	 */
 	long mmp_last_written;
+
+	/* Precomputed FS UUID checksum for seeding other checksums */
+	__u32 csum_seed;
 };
 
 #if EXT2_FLAT_INCLUDES
@@ -1438,6 +1441,7 @@ extern errcode_t ext2fs_write_bb_FILE(ext2_badblocks_list bb_list,
 
 
 /* inline functions */
+extern void ext2fs_init_csum_seed(ext2_filsys fs);
 extern errcode_t ext2fs_get_mem(unsigned long size, void *ptr);
 extern errcode_t ext2fs_get_memalign(unsigned long size,
 				     unsigned long align, void *ptr);
@@ -1490,6 +1494,16 @@ extern int ext2fs_fstat(int fd, ext2fs_struct_stat *buf);
 
 #ifndef EXT2_CUSTOM_MEMORY_ROUTINES
 #include <string.h>
+_INLINE_ void ext2fs_init_csum_seed(ext2_filsys fs)
+{
+	if (!EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return;
+
+	fs->csum_seed = ext2fs_crc32c_le(~0, fs->super->s_uuid,
+					 sizeof(fs->super->s_uuid));
+}
+
 /*
  *  Allocate memory
  */
diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index 32e068c..10beb06 100644
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -298,6 +298,8 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
 		retval = EXT2_ET_CORRUPT_SUPERBLOCK;
 		goto cleanup;
 	}
+	/* Precompute the FS UUID to seed other checksums */
+	ext2fs_init_csum_seed(fs);
 
 	/*
 	 * Read group descriptors
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index c70c1b4..d80c0b2 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -2318,6 +2318,7 @@ int main (int argc, char *argv[])
 		}
 	} else
 		uuid_generate(fs->super->s_uuid);
+	ext2fs_init_csum_seed(fs);
 
 	/*
 	 * Initialize the directory index variables

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