Re: ext3 and SPEC SFS Run rules.

[Andrew Morton <akpm@osdl.org>]

Tigran Aivazian <tigran@aivazian.fsnet.co.uk> wrote:
>
> I have a simple question --- does ext3 conform to the SPEC SFS Run rules 
>  with default mount options or does one need to force the correct 
>  behaviour by mounting in some "special" way?. Here is the URL for the 
>  rules:
> 
>    http://www.spec.org/sfs97r1/docs/runrules.html
> 
>  In particular, the bit that is worrying me is:
> 
>    For NFS Version 3, the server adheres to the protocol specification. In 
>    particular the requirement that for STABLE write requests and COMMIT 
>    operations the NFS server must not reply to the NFS client before any 
>    modified file system data or metadata, with the exception of access times, 
>    are written to stable storage for that specific or related operation. 
>    See RFC 1813, NFSv3 protocol specification for a definition of STABLE 
>    and COMMIT for NFS write requests.
> 
>  As far as I can see from nfsd source this means:
> 
>  a) write with 'stable' flag set does a f_op->write() with O_SYNC.
> 
>  b) COMMIT3 just means f_op->fsync().
> 
>  So, the question is really --- do ext3 O_SYNC write and fsync require some 
>  special mount options to work _properly_ or are they fine by default?
> 
>  Looking at ext3_sync_file() it seems OK by default.
> 
>  However, looking at ext3 ->write() operation it seems to forcibly commit 
>  only if it is mounted with EXT3_MOUNT_JOURNAL_DATA option (or if it is not 
>  a regular file or if EXT3_JOURNAL_DATA_FL inode flag is set).

ext3 should be fully syncing data and metadata for both fsync() and O_SYNC
writes in all three journalling modes.  If not, that's a big bug.