Re: [PATCH] Btrfs: fix warning of free_extent_map

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Mar 15, 2013 at 10:46:39PM +0800, Liu Bo wrote:
> Users report that an extent map's list is still linked when it's actually
> going to be freed from cache.
> 
> The story is that
> 
> a) when we're going to drop an extent map and may split this large one into
> smaller ems, and if this large one is flagged as EXTENT_FLAG_LOGGING which means
> that it's on the list to be logged, then the smaller ems split from it will also
> be flagged as EXTENT_FLAG_LOGGING, and this is _not_ expected.
> 
> b) we'll keep ems from unlinking the list and freeing when they are flagged with
> EXTENT_FLAG_LOGGING, because the log code holds one reference.
> 
> The end result is the warning, but the truth is that we set the flag
> EXTENT_FLAG_LOGGING only during fsync.
> 
> So clear flag EXTENT_FLAG_LOGGING for extent maps split from a large one.
> 
> Reported-by: Johannes Hirte <johannes.hirte@fem.tu-ilmenau.de>
> Reported-by: Darrick J. Wong <darrick.wong@oracle.com>
> Signed-off-by: Liu Bo <bo.li.liu@oracle.com>

This seems to fix my problem, so you can add:
Tested-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/btrfs/file.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> index 83c790d..7bdb47f 100644
> --- a/fs/btrfs/file.c
> +++ b/fs/btrfs/file.c
> @@ -591,6 +591,7 @@ void btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
>  		}
>  		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
>  		clear_bit(EXTENT_FLAG_PINNED, &em->flags);
> +		clear_bit(EXTENT_FLAG_LOGGING, &flags);
>  		remove_extent_mapping(em_tree, em);
>  		if (no_splits)
>  			goto next;
> -- 
> 1.7.7.6
>