From: Ted Ts'o <tytso@mit.edu>
To: Andreas Dilger <adilger@dilger.ca>
Cc: "Darrick J. Wong" <djwong@us.ibm.com>, linux-ext4@vger.kernel.org
Subject: Re: Collapsing the number of feature flags (was Re: [PATCH v2.3 00/23] ext4: Add metadata checksumming)
Date: Sat, 11 Feb 2012 21:55:18 -0500 [thread overview]
Message-ID: <20120212025518.GA22492@thunk.org> (raw)
In-Reply-To: <28776282-021D-473A-99A1-F5A3DDC08966@dilger.ca>
On Sat, Feb 11, 2012 at 06:38:03PM -0700, Andreas Dilger wrote:
>
> I think that making it difficult for users to use anything but the default
> options in mke2fs/tune2fs/debugfs is equivalent to what you suggest.
> Unless you prevent the use of the old feature flags entirely, then it
> would still be possible to create filesystems with mixed up combinations
> of features. I think the important outcome is that users are clearly
> made aware that they are stepping off the well-trodden path, and if
> things break they get to keep both pieces. Having two feature flags
> that mean the same thing doesn't really help this, IMHO.
The problem is that sometimes people upgrade the kernel before they
upgrade userspace, and sometimes they upgrade e2fsprogs but are still
running an older kernel --- and there times when those are good and
proper things to do (i.e., they have to use some ancient obsolete RHEL
kernel becuase it's they only way they can talk to the EMC storage
device, but they want to use a newer e2fsprogs to fix bugs that have
since been fixed in the latest version of e2fsprogs).
So we have to support both, and so yes, we can't remove any code for
quite a while. What we *can* do is say that if you enable metadata
checksums, you also must get all of these other features along for the
ride. It's true that means users can still create mixed up feature
set --- but not if they want the new metadata checksum feature.
It's an eventual solution, but it's not magic pixie dust, yes.
Realistically most of the time we haven't had *that* many problems
caused by random feature combinations. There are certain combinations
that are problematic, but we know what they are up front.
If someone really wants to add that screen for certain feature
combinations and causes mke2fs/e2fsck to complain, or maybe even
outright refuse to function, that's a different thing, that's going to
be fairly specific for the distro. I don't think that's something we
want to add upstream....
- Ted
prev parent reply other threads:[~2012-02-12 2:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-07 8:27 [PATCH v2.3 00/23] ext4: Add metadata checksumming Darrick J. Wong
2012-01-07 8:27 ` [PATCH 01/23] ext4: Create a new BH_Verified flag to avoid unnecessary metadata validation Darrick J. Wong
2012-01-07 8:28 ` [PATCH 02/23] ext4: Change on-disk layout to support extended metadata checksumming Darrick J. Wong
2012-01-07 8:28 ` [PATCH 03/23] ext4: Record the checksum algorithm in use in the superblock Darrick J. Wong
2012-01-07 8:28 ` [PATCH 04/23] ext4: Only call out to crc32c if necessary Darrick J. Wong
2012-01-07 8:28 ` [PATCH 05/23] ext4: Calculate and verify superblock checksum Darrick J. Wong
2012-01-07 8:28 ` [PATCH 06/23] ext4: Calculate and verify inode checksums Darrick J. Wong
2012-01-07 8:28 ` [PATCH 07/23] ext4: Calculate and verify checksums for inode bitmaps Darrick J. Wong
2012-01-07 8:28 ` [PATCH 08/23] ext4: Calculate and verify block bitmap checksum Darrick J. Wong
2012-01-07 8:28 ` [PATCH 09/23] ext4: Verify and calculate checksums for extent tree blocks Darrick J. Wong
2012-01-07 8:28 ` [PATCH 10/23] ext4: Calculate and verify checksums for htree nodes Darrick J. Wong
2012-01-07 8:29 ` [PATCH 11/23] ext4: Calculate and verify checksums of directory leaf blocks Darrick J. Wong
2012-01-07 8:29 ` [PATCH 12/23] ext4: Calculate and verify checksums of extended attribute blocks Darrick J. Wong
2012-01-07 8:29 ` [PATCH 13/23] ext4: Add new feature to make block group checksums use metadata_csum algorithm Darrick J. Wong
[not found] ` <8ED6E1F9-DB56-4D31-BCA8-2A3A8D514BD5@dilger.ca>
2012-02-13 22:28 ` Ted Ts'o
2012-02-29 1:27 ` [RFC] e2fsprogs: Rework metadata_csum/gdt_csum flag handling Darrick J. Wong
2012-02-29 5:40 ` Andreas Dilger
2012-03-03 3:50 ` [RFC v2] " Darrick J. Wong
2012-02-29 1:32 ` [RFC] ext4: Rework metadata_csum/gdt_csum flag handling in kernel Darrick J. Wong
2012-02-29 5:48 ` Andreas Dilger
2012-03-03 3:56 ` [RFC v2] " Darrick J. Wong
2012-01-07 8:29 ` [PATCH 14/23] ext4: Add checksums to the MMP block Darrick J. Wong
2012-01-07 8:29 ` [PATCH 15/23] jbd2: Change disk layout for metadata checksumming Darrick J. Wong
2012-01-07 8:29 ` [PATCH 16/23] jbd2: Enable journal clients to enable v2 checksumming Darrick J. Wong
2012-01-07 8:29 ` [PATCH 17/23] jbd2: Grab a reference to the crc32c driver only when necessary Darrick J. Wong
2012-01-07 8:29 ` [PATCH 18/23] jbd2: Checksum journal superblock Darrick J. Wong
2012-01-07 8:30 ` [PATCH 19/23] jbd2: Checksum revocation blocks Darrick J. Wong
2012-01-07 8:30 ` [PATCH 20/23] jbd2: Checksum descriptor blocks Darrick J. Wong
2012-01-07 8:30 ` [PATCH 21/23] jbd2: Checksum commit blocks Darrick J. Wong
2012-01-07 8:30 ` [PATCH 22/23] jbd2: Checksum data blocks that are stored in the journal Darrick J. Wong
2012-01-07 8:30 ` [PATCH 23/23] ext4/jbd2: Add metadata checksumming to the list of supported features Darrick J. Wong
2012-02-08 18:08 ` Collapsing the number of feature flags (was Re: [PATCH v2.3 00/23] ext4: Add metadata checksumming) Ted Ts'o
2012-02-09 19:54 ` Darrick J. Wong
2012-02-09 22:49 ` Ted Ts'o
2012-02-10 19:11 ` Andreas Dilger
2012-02-10 21:11 ` Ted Ts'o
2012-02-12 1:38 ` Andreas Dilger
2012-02-12 2:55 ` Ted Ts'o [this message]
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