Re: Does data checksumming remain for files with No_COW file attribute?

[Christoph Anton Mitterer <calestyo@scientia.net>]

[-- Attachment #1: Type: text/plain, Size: 985 bytes --]

On Sat, 2016-09-24 at 17:40 +0500, Roman Mamedov wrote:
> Yes. IIRC the reasoning was that it's more difficult to track
> checksums of
> data which is being overwritten in-place (as opposed to CoW).
AFAIU it wouldn't be more difficult, since the meta-data itself is
still subject to CoW...

There's just no guarantee in the case of a crash, that checksum and
data match (which is IMO however a small price to pay - especially as
the data is in that case and without CoW anyway not guaranteed to be
valid - compared to all sorts of other silent corruptions against which
checksums protect... not to talk about the ability to actually repair
files in case of RAID inconsistencies.


> You can't apply chattr +C to any files of non-zero length, so by
> definition
> there won't be any pre-existing checksummed extents in that file.

Speaking of which,... can't one modify chattr properly so that it gives
an error message and $? != 0 in that case?


Cheers,
Chris.

[-- Attachment #2: smime.p7s --]
[-- Type: application/x-pkcs7-signature, Size: 5930 bytes --]