From: Ted Ts'o <tytso@mit.edu>
To: "Darrick J. Wong" <djwong@us.ibm.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH 19/22] jbd2: Checksum revocation blocks
Date: Mon, 12 Dec 2011 10:39:35 -0500 [thread overview]
Message-ID: <20111212153935.GA13213@thunk.org> (raw)
In-Reply-To: <20111128232829.19194.79159.stgit@elm3c44.beaverton.ibm.com>
On Mon, Nov 28, 2011 at 03:28:29PM -0800, Darrick J. Wong wrote:
> + /*
> + * Ignoring corrupt revoke blocks is safe
> + * because at worst it results in unnecessary
> + * writes during recovery.
> + */
This is *not* true. The reason why we have revoke blocks is because
we have to handle the case where a metadata block (which is journaled)
is released, and then the block is reused as a data block. If we then
replay the block, the "unnecessary write" will result the potential
corruption of a data block.
So if we lose a revoke block, it's not possible to safely replay *any*
part of the journal. E2fsck might be able to do something about it by
saving the old copy of all blocks written during the journal replay if
it detects this case, and then alerting the system administrator that
a particular data file may have gotten corrupted. But it's going to
be really messy...
- Ted
next prev parent reply other threads:[~2011-12-12 15:39 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
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 [this message]
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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