From: Eric Sandeen <sandeen@redhat.com>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@dilger.ca>,
ext4 development <linux-ext4@vger.kernel.org>
Subject: Re: Journal under-reservation bug on first >2G file
Date: Thu, 02 Oct 2014 00:49:09 -0500 [thread overview]
Message-ID: <542CE755.9040503@redhat.com> (raw)
In-Reply-To: <20141001224325.GE2903@thunk.org>
On 10/1/14 5:43 PM, Theodore Ts'o wrote:
> On Wed, Oct 01, 2014 at 03:37:17PM -0500, Eric Sandeen wrote:
>>
>> Ok. I guess this is only an issue for ext4 - well, at least this specific
>> issue. Delalloc makes it much different than ext2 & ext3, which reserve quite a
>> lot more. Whether there's a corner case over there which breaks, I dunno...
>>
>> So it seems like the simplest test is simply: Are we RW mounted with delalloc?
>> And if so, update the feature. Seems simpler than mucking with "which features
>> are unique to ext4"
>
> I'd do "are we RW mounted with the extents feature". That way we
> don't need to worry about someone accidentally mounting a partition
> meant for Hurd using ext4, which would imply delalloc, and then
> causing Hurd to no longer be able to deal with the file system. That
> *shouldn't* happen, but if someone accidentally mounts the file system
> with -t ext4, but it seems safer to gate it on the existence of the
> extents feature.
Problem is, we can hit the same problem with an ext3 filesystem (no
extents) mounted with -t ext4 (enabling delalloc).
Ugh. Can't we just bump the da write reservation to 2 and be done with it? ;)
(AFAICT the non-delalloc reservations can be wildly overestimated).
Or maybe ext4_journal_extend() when we try to update the superblock?
It could fail, but it wouldn't be catastrophic if it did, fsck would find
that the feature is missing...
-Eric
next prev parent reply other threads:[~2014-10-02 5:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-30 21:10 Journal under-reservation bug on first >2G file Eric Sandeen
2014-09-30 21:22 ` Eric Sandeen
2014-09-30 21:36 ` Andreas Dilger
2014-09-30 22:10 ` Darrick J. Wong
2014-10-01 11:53 ` Theodore Ts'o
2014-10-01 14:43 ` Eric Sandeen
2014-10-01 19:59 ` Theodore Ts'o
2014-10-01 20:37 ` Eric Sandeen
2014-10-01 22:43 ` Theodore Ts'o
2014-10-02 5:49 ` Eric Sandeen [this message]
2014-10-02 11:26 ` Jan Kara
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