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SubjectRe: Is ReiserFS really a journaling file system, or is it really just a synchronous-metadata file system like BSD FFS?
On Wed, 29 Mar 2000, Chris Mason wrote:

>[ for protecting files from corrupt data ]

Yep. More precisely what I meant was to protect files from having random
contents that was previously on disk before the first data write to the
file (that's also _the_ security issue).

>> reiserfs should be able to provide that feature too without having data
>> journaling with some additional care in the way the data is exposed to
>> userspace (mount option probably).
>>
>I think I see what you mean...perhaps we could do this by updating the
>stat data to reflect which blocks have actually been written. If we read

Yes, something like that. The end_io of the data bh can set a bitflag in
the inode that means such block is not containing sniffable/random data
anymore but that it contains something related to _such_ file.

>a file that is incomplete, we have a choice of truncating off the bad
>data, or simply refusing to service any operations for that file. Or did
>you intend something else (my idea wouldn't be zero cost).

Yes, it's definitely not zero cost (the inode gets dirtified also at the
end_io of the data block) but it would take care at least of the security
issue and of the completly random data in the file that is the bigger
concern as far I can tell.

For full data integrity data journaling is necessary instead.

Andrea


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