lkml.org 
[lkml]   [2012]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v2 1/7] Adding support to freeze and unfreeze a journal
From
> > Hrm let me think through this a little more; we actually do:
> >
> > t16) ext4_journal_start()
> >   t17) ext4_journal_start_sb()
> >     t18) handle = ext4_journal_current_handle();
> >     t19) if (!handle) vfs_check_frozen()
> >     t20) ... jbd2_journal_start()
>  Ah, right. I forgot.
>
> > So actually we *do* block new handles, but let *existing* ones
> > continue (see commits 6b0310fbf087ad6e9e3b8392adca97cd77184084
> > and be4f27d324e8ddd57cc0d4d604fe85ee0425cba9)
> >
> > So your assertion that a new handle is started is incorrect
> > in general, isn't it?  So then does the fix seem necessary?
> > Or, at least, in the fashion below - maybe we need to just make
> > sure all started handles complete before the unlock_updates?
> > Or am I missing something...?
>  Well, the problem with running operations and freezing is more
> fundamental I believe. See my email
> http://marc.info/?l=linux-fsdevel&m=132585911925796&w=2
>
> So I believe we'll need some better exclusion mechanism already in VFS.
>
>                                                                Honza
>

If all the write operations were journaled, then this patch would not
allow ext4 filesystem to have any dirty data after its frozen.
(as journal_start() would block).

I think the only one candidate that creates dirty data without
calling ext4_journal_start() is mmapped?

Regards,
Surbhi.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2012-01-10 22:57    [W:0.051 / U:0.452 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site