Re: [PATCH V2] xfs: make src file readable during reflink

[Dave Chinner <david@fromorbit.com>]

On Tue, Jun 28, 2022 at 03:57:14PM +0000, Wengang Wang wrote:
> Hi Darrick,
> 
> How about the V2?
> 
> thanks,
> wengang
> 
> > On Jun 24, 2022, at 12:10 PM, Wengang Wang <wen.gang.wang@oracle.com> wrote:
> > 
> > During a reflink operation, the IOLOCK and MMAPLOCK of the source file
> > are held in exclusive mode for the duration. This prevents reads on the
> > source file, which could be a very long time if the source file has
> > millions of extents.
> > 
> > As the source of copy, besides some necessary modification (say dirty page
> > flushing), it plays readonly role. Locking source file exclusively through
> > out the full reflink copy is unreasonable.
> > 
> > This patch downgrades exclusive locks on source file to shared modes after
> > page cache flushing and before cloning the extents. To avoid source file
> > change after lock downgradation, direct write paths take IOLOCK_EXCL on
> > seeing reflink copy happening to the files.
> > 
> > Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
> > ---
> > V2 changes:
> > Commit message
> > Make direct write paths take IOLOCK_EXCL when reflink copy is happening
> > Tiny changes

Version 2 never made it to the list. Please resend.

-Dave.
-- 
Dave Chinner
david@fromorbit.com