Re: [PATCH 3/3 v2] dax: use pfn_mkwrite to update c/mtime + freeze protection

[Jan Kara <jack@suse.cz>]

On Thu 05-03-15 12:47:30, Boaz Harrosh wrote:
> On 03/05/2015 12:35 PM, Jan Kara wrote:
> > On Thu 05-03-15 11:32:25, Boaz Harrosh wrote:
> >> On 03/05/2015 11:24 AM, Boaz Harrosh wrote:
> <>
> >>
> >> Just as curiosity, does the freezing code goes and turns all mappings
> >> into read-only, Also for pfn mapping?
> >   Hum, that's a good question. Probably we don't end up doing that. For
> >
> > normal filesystems we sync all inodes which also writeprotects all pages
> > (in clear_page_dirty_for_io() - for normal filesystems we know that if page
> > is writeably mapped it is dirty). However this won't happen for pfn
> > mapping as we don't have dirty pages. So we probably need dax_freeze()
> > implementation that will walk through all inodes with writeable mappings and
> > writeprotect them.
> > 
> 
> I'll go head and try my shot on implementing a dax_freeze(). But I will
> please need help with where to call it from.
> 
> Probably something like:
> 	if (IS_DAX(inode))
> 		dax_freeze(inode);
> 	else
> 		sync(inode)
  We normally call sync_filesystem() from fs/superblock:freeze_super(). For
DAX filesystems we'd also need to call the special function after that.
Maybe dax_freeze() isn't the best name. It could be called something like
dax_writeprotect(sb) or something like that.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

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