[PATCH] Btrfs: fix return code in drop_objectid_items

[PATCH] Btrfs: fix return code in drop_objectid_items

[Josef Bacik]

So dpkg fsync()'s the file and the directory containing the file whenever it
writes to a file which is really slow in btrfs.  This is partly because
fsync()'ing a directory _always_ committed the transaction instead of just
going to the tree log.  This is because drop_objectid_items() would return 1
since it does a btrfs_search_slot() which returns 1.  In tree-log jargon
this means that we have to commit the transaction to be safe.  So just check
if ret is greater than 0 and set it to 0 if it does.  With this patch we now
use the tree-log instead of committing the entire transaction, which is
twice as fast on my box.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
---
 fs/btrfs/tree-log.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 425014b..2017d0f 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2667,6 +2667,8 @@ static int drop_objectid_items(struct btrfs_trans_handle *trans,
 		btrfs_release_path(path);
 	}
 	btrfs_release_path(path);
+	if (ret > 0)
+		ret = 0;
 	return ret;
 }
 
-- 
1.7.7.6

Re: [PATCH] Btrfs: fix return code in drop_objectid_items

[Liu Bo]

On 05/30/2012 04:57 AM, Josef Bacik wrote:

> So dpkg fsync()'s the file and the directory containing the file whenever it
> writes to a file which is really slow in btrfs.  This is partly because
> fsync()'ing a directory _always_ committed the transaction instead of just
> going to the tree log.  This is because drop_objectid_items() would return 1
> since it does a btrfs_search_slot() which returns 1.  In tree-log jargon
> this means that we have to commit the transaction to be safe.  So just check
> if ret is greater than 0 and set it to 0 if it does.  With this patch we now
> use the tree-log instead of committing the entire transaction, which is
> twice as fast on my box.  Thanks,
> 


Good catch.

Reviewed-by: Liu Bo <liubo2009@cn.fujitsu.com>

> Signed-off-by: Josef Bacik <josef@redhat.com>
> ---
>  fs/btrfs/tree-log.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
> index 425014b..2017d0f 100644
> --- a/fs/btrfs/tree-log.c
> +++ b/fs/btrfs/tree-log.c
> @@ -2667,6 +2667,8 @@ static int drop_objectid_items(struct btrfs_trans_handle *trans,
>  		btrfs_release_path(path);
>  	}
>  	btrfs_release_path(path);
> +	if (ret > 0)
> +		ret = 0;
>  	return ret;
>  }
>