Re: [PATCH 2/6] f2fs: support goingdown for fs shutdown

[Jaegeuk Kim <jaegeuk@kernel.org>]

On Fri, Jan 09, 2015 at 09:04:12AM +1100, Dave Chinner wrote:
> On Thu, Jan 08, 2015 at 01:21:29PM -0800, Jaegeuk Kim wrote:
> > On Fri, Jan 09, 2015 at 07:54:16AM +1100, Dave Chinner wrote:
> > > On Thu, Jan 08, 2015 at 02:33:17PM -0600, Eric Sandeen wrote:
> > > > On 1/8/15 2:18 PM, Jaegeuk Kim wrote:
> > > > > On Thu, Jan 08, 2015 at 01:54:20PM -0600, Eric Sandeen wrote:
> > > > >> On 1/8/15 12:10 PM, Jaegeuk Kim wrote:
> > > > >>> This patch add an ioctl to shutdown f2fs, which stops all the further block
> > > > >>> writes after this point.
> > > > >>
> > > > >> would it make sense to just re-use the xfs ioctl nr, if the semantics are
> > > > >> the same?
> > > > > 
> > > > > The semantics are not same for now.
> > > > > In order to reuse xfs ioctl, it needs to support options for flushing logs.
> > > > 
> > > > the xfs iotl has 3 behaviors optional:
> > > > 
> > > > #define XFS_FSOP_GOING_FLAGS_DEFAULT            0x0     /* going down */
> > > > #define XFS_FSOP_GOING_FLAGS_LOGFLUSH           0x1     /* flush log but not data */
> > > > #define XFS_FSOP_GOING_FLAGS_NOLOGFLUSH         0x2     /* don't flush log nor data */
> > > > 
> > > > if f2fs currently supports a subset, you could just -EOPNOTSUPP on the others.
> > > 
> > > No, just do a default shutdown operation if the semantics cannot be
> > > supported.
> > > 
> > > 	- XFS_FSOP_GOING_FLAGS_DEFAULT ==
> > > 		consistent on disk before shutdown
> > > 			+ implemented by freeze/thaw/shutdown sequence
> > > 	- XFS_FSOP_GOING_FLAGS_LOGFLUSH ==
> > > 		consistent journal on disk before shutdown
> > > 			+ implemented by journal flush/shutdown sequence
> 
> I should point out that this is really "consistent metadata on
> disk before shutdown", so it really doesn't matter if your
> filesystem has a journal or not, it can still be implemented.

Agreed. I just implemented these three options for f2fs.

For the f2fs perspective, DEFAULT conducts
 - flushing all the user and dentry blocks
 - checkpointing and then shutdowning fs

LOGFLUSH conducts
 - checkpointing and then shutdowning fs

NOLOGFLUSH conducts
 - shutdowning fs

> 
> Perhaps it woul dbe best to rename them for a generic ioctl
> to FS_GOING_DOWN_SYNC, FS_GOING_DOWN_METADATA_METASYNC
> and FS_GOING_DOWN_NOSYNC...

How about FS_GOING_DOWN_FULLSYNC, FS_GOING_DOWN_METASYNC, and
FS_GOING_DOWN_NOSYNC?

Thanks,

> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david@fromorbit.com

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