On Wed, 2007-01-24 at 09:40 -0800, Mingming Cao wrote:
> Cordenner jean noel wrote:
> > Andreas Dilger a écrit :
> >
> >> On Jan 23, 2007 18:23 +0100, Cordenner jean noel wrote:
> >>
> >>> I've updated what was previously the change attribute patch for ext4
> >>> initially posted by Alexandre Ratchov. The previous patch was
> >>> introducing a change_attribute field, now it uses the i_version field of
> >>> the inode.
> >>>
> >>> The i_version field is a counter that is set on every inode creation and
> >>> that is incremented every time the inode data is modified (similarly to
> >>> the "ctime" time-stamp).
> >>> The aim is to fulfill NFSv4 requirements for rfc3530.
> >>> For the moent, the counter is only a 32bit value but it is planned to be
> >>> 64bit as required.
> >>>
> >>> The patch is divided into 3 parts, the vfs layer, the ext4 specific code
> >>> and an user part to check i_version changes via stat.
> >>
> >>
> >> Have you had a chance to look at the performance impact of this change
> >> (possible with oprofile)? Always marking the inodes dirty for ext3
> >> may have some noticable overhead.
> >>
> >
> > I did some tests using fileop with the previous version of the patch
> > which was very similar. I was surprised that there was no noticable
> > overhead:
> > http://www.bullopensource.org/ext4/change_attribute/index.html
> >
> > I will use oprofile to check it again.
>
> Could we just increment the counter each time the mtime is modifies(not
> the ctime)? Is that enough to serve NFSv4 need?
No. That would not conform to RFC3530:
5.5. Mandatory Attributes - Definitions
Name # DataType Access Description
___________________________________________________________________
.....
change 3 uint64 READ A value created by the
server that the client
can use to determine
if file data,
directory contents or
attributes of the
object have been
modified. The server
may return the
object's time_metadata
attribute for this
attribute's value but
only if the filesystem
object can not be
updated more
frequently than the
resolution of
time_metadata.
so the change attribute needs to change on both data and metadata
updates.
Cheers,
Trond
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