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

[Liu Bo <bo.li.liu@oracle.com>]

On Fri, Jul 25, 2014 at 09:53:43AM +0800, Wang Shilong wrote:
> On 07/24/2014 10:48 PM, Liu Bo wrote:
> >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;
> BTW, if such ENOSPC happens, it means we could not reserve compressed space.
> So we retry with nocompression codes, it will try to reserve more
> space. Any reason
> we do such things?

Compressed extents needs continuous space while uncompressed extents can have
more choices.

thanks,
-liubo

> 
> Thanks,
> Wang
> >  			}
> >  			goto out_free;
>