From: "Darrick J. Wong" <djwong@us.ibm.com>
To: "Ted Ts'o" <tytso@mit.edu>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH 02/22] ext4: Create a rocompat flag for extended metadata checksumming
Date: Mon, 5 Dec 2011 11:24:50 -0800 [thread overview]
Message-ID: <20111205192450.GA7137@tux1.beaverton.ibm.com> (raw)
In-Reply-To: <20111205154133.GA5488@thunk.org>
On Mon, Dec 05, 2011 at 10:41:33AM -0500, Ted Ts'o wrote:
> (Reviews sent to ext4 list only)
>
> On Mon, Nov 28, 2011 at 03:26:29PM -0800, Darrick J. Wong wrote:
> > This patch introduces a rocompat feature flag to signal the presence
> > of checksums for metadata blocks. It also provides storage for a
> > precomputed UUID checksum.
> >
> > +
> > + /* Precomputed FS UUID checksum */
> > + __u32 s_uuid_csum;
>
> This is really a checksum seed, right? Calling it a UUID is going to
> be confusing because UUID's are expected to be 128 bits, and something
> which is 32 bits can't possibly be a universally unique.
It's the checksum of the FS UUID, so I guess 'seed' describes it. I wasn't
trying to call it a UUID.
I also need to clarify the changelog, apparently. s_uuid_csum is *in-core*
storage for a precomputed UUID checksum. This piece (and i_uuid_inum_csum) are
computed at load time, just in case the user changed the UUID when the fs was
offline.
> I'd suggest calling this "s_csum_seed", and we explain it as a
> random seed which is selected when the file system is formatted.
Not necessarily random, since you can mkfs.ext4 -U.
> The commit description could also explain that this is used so we can
> detect old metadata blocks left over from a previous use of the
> storage device.
Ok.
--D
next prev parent reply other threads:[~2011-12-05 19:25 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-28 23:26 [PATCH v2.1 00/22] ext4: Add metadata checksumming Darrick J. Wong
2011-11-28 23:26 ` [PATCH 01/22] ext4: Create a new BH_Verified flag to avoid unnecessary metadata validation Darrick J. Wong
2011-11-28 23:26 ` [PATCH 02/22] ext4: Create a rocompat flag for extended metadata checksumming Darrick J. Wong
2011-12-05 15:41 ` Ted Ts'o
2011-12-05 19:24 ` Darrick J. Wong [this message]
2011-11-28 23:26 ` [PATCH 03/22] ext4: Record the checksum algorithm in use in the superblock Darrick J. Wong
2011-12-05 15:46 ` Ted Ts'o
2011-12-05 19:32 ` Darrick J. Wong
[not found] ` <E0964BB6-793D-49AF-A2B0-20748C6DAE2B@dilger.ca>
2011-12-07 7:42 ` Darrick J. Wong
2011-12-07 8:40 ` Andreas Dilger
2011-11-28 23:26 ` [PATCH 04/22] ext4: Only call out to crc32c if necessary Darrick J. Wong
2011-12-05 15:52 ` Ted Ts'o
2011-12-05 19:38 ` Darrick J. Wong
2011-11-28 23:26 ` [PATCH 05/22] ext4: Calculate and verify superblock checksum Darrick J. Wong
2011-11-28 23:26 ` [PATCH 06/22] ext4: Calculate and verify inode checksums Darrick J. Wong
2011-12-05 16:24 ` Ted Ts'o
2011-12-05 19:45 ` Darrick J. Wong
2011-11-28 23:27 ` [PATCH 07/22] ext4: Create bitmap checksum helper functions Darrick J. Wong
2011-12-05 16:33 ` Ted Ts'o
2011-12-05 20:31 ` Darrick J. Wong
2011-12-05 23:54 ` Darrick J. Wong
2011-12-06 17:19 ` Andreas Dilger
2011-12-06 20:59 ` Darrick J. Wong
2011-11-28 23:27 ` [PATCH 08/22] ext4: Calculate and verify checksums for inode bitmaps Darrick J. Wong
2011-11-28 23:27 ` [PATCH 09/22] ext4: Calculate and verify block bitmap checksum Darrick J. Wong
2011-11-28 23:27 ` [PATCH 10/22] ext4: Verify and calculate checksums for extent tree blocks Darrick J. Wong
2011-12-05 16:40 ` Ted Ts'o
2011-12-05 19:50 ` Darrick J. Wong
2011-11-28 23:27 ` [PATCH 11/22] ext4: Calculate and verify checksums for htree nodes Darrick J. Wong
2011-11-28 23:27 ` [PATCH 12/22] ext4: Calculate and verify checksums of directory leaf blocks Darrick J. Wong
2011-11-28 23:27 ` [PATCH 13/22] ext4: Calculate and verify checksums of extended attribute blocks Darrick J. Wong
2011-11-28 23:27 ` [PATCH 14/22] ext4: Add new feature to make block group checksums use metadata_csum algorithm Darrick J. Wong
2011-11-28 23:28 ` [PATCH 15/22] ext4: Add checksums to the MMP block Darrick J. Wong
2011-11-28 23:28 ` [PATCH 16/22] jbd2: Update structure definitions and flags to support extended checksumming Darrick J. Wong
2011-11-28 23:28 ` [PATCH 17/22] jbd2: Grab a reference to the crc32c driver only when necessary Darrick J. Wong
2011-11-28 23:28 ` [PATCH 18/22] jbd2: Update structure definitions and flags to support extended checksumming Darrick J. Wong
2011-11-28 23:28 ` [PATCH 19/22] jbd2: Checksum revocation blocks Darrick J. Wong
2011-12-12 15:39 ` Ted Ts'o
2011-11-28 23:28 ` [PATCH 20/22] jbd2: Checksum descriptor blocks Darrick J. Wong
2011-11-28 23:28 ` [PATCH 21/22] jbd2: Checksum commit blocks Darrick J. Wong
2011-11-28 23:28 ` [PATCH 22/22] jbd2: Checksum data blocks that are stored in the journal Darrick J. Wong
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