Re: [PATCH] Btrfs: fix compressed write corruption on enospc

[Martin Steigerwald <Martin@lichtvoll.de>]

Am Montag, 4. August 2014, 14:50:29 schrieb Martin Steigerwald:
> Am Freitag, 25. Juli 2014, 11:54:37 schrieb Martin Steigerwald:
> > Am Donnerstag, 24. Juli 2014, 22:48:05 schrieben Sie:
> > > When failing to allocate space for the whole compressed extent, we'll
> > > fallback to uncompressed IO, but we've forgotten to redirty the pages
> > > which belong to this compressed extent, and these 'clean' pages will
> > > simply skip 'submit' part and go to endio directly, at last we got data
> > > corruption as we write nothing.
> > >
> > > 
> > >
> > > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > > ---
> > >
> > > 
> > >  fs/btrfs/inode.c | 12 ++++++++++++
> > >  1 file changed, 12 insertions(+)
> > > 
> > >
> > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > > index 3668048..8ea7610 100644
> > > --- a/fs/btrfs/inode.c
> > > +++ b/fs/btrfs/inode.c
> > >
> > > 
> > >
> > > @@ -709,6 +709,18 @@ retry:
> > >                             unlock_extent(io_tree, async_extent->start,
> > >                             
> > >                                           async_extent->start +
> > >                                           async_extent->ram_size - 1);
> > > 
> > >
> > > +
> > > +                           /*
> > > +                            * we need to redirty the pages if we decide
> > > to
> > > +                            * fallback to uncompressed IO, otherwise we
> > > +                            * will not submit these pages down to lower
> > > +                            * layers.
> > > +                            */
> > > +                           extent_range_redirty_for_io(inode,
> > > +                                           async_extent->start,
> > > +                                           async_extent->start +
> > > +                                           async_extent->ram_size - 1);
> > > +
> > >
> > > 
> > >                             goto retry;
> > >                     
> > >                     }
> > >                     goto out_free;
> >
> > 
> >
> > I am testing this currently. So far no lockup. Lets see. Still has not
> >
> > filled the the block device with trees completely after I balanced them:
> > 
> >
> > Label: 'home'  uuid: […]
> >
> >         Total devices 2 FS bytes used 125.57GiB
> >         devid    1 size 160.00GiB used 153.00GiB path /dev/dm-0
> >         devid    2 size 160.00GiB used 153.00GiB path
> >/dev/mapper/sata-home 
> >
> > I believe the lockups happen more easily if the trees occupy all of disk
> > space. Well I will do some compiling of some KDE components which may let
> > BTRFS fill all space again.
> >
> > 
> >
> > This patch will mean it when it can´t make enough free space in the
> > (fragmented) tree it will write uncompressed?
> >
> > 
> >
> > This would mean that one would have a defragment trees regularily to allow
> > for writes to happen compressed at all times.
> >
> > 
> >
> > Well… of course still better than lockup or corruption.
> 
> So lookups so far anymore.

No lookups of course.

-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
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