Re: [PATCH] Btrfs: fix what bits we clear when erroring out from delalloc

[Miao Xie <miaox@cn.fujitsu.com>]

On mon, 29 Jul 2013 13:24:22 -0400, Josef Bacik wrote:
> First of all we no longer set EXTENT_DIRTY when we dirty an extent so this patch
> removes the clearing of EXTENT_DIRTY since it confuses me.  This patch also adds
> clearing EXTENT_DEFRAG and also doing EXTENT_DO_ACCOUNTING when we have errors.
> This is because if we are clearing delalloc without adding an ordered extent
> then we need to make sure the enospc handling stuff is accounted for.  Also if
> this range was DEFRAG we need to make sure that bit is cleared so we dont leak
> it.  Thanks,
> 
> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
> ---
>  fs/btrfs/inode.c |   46 ++++++++++++++++++++++++++--------------------
>  1 files changed, 26 insertions(+), 20 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index a60be02..686ba5c 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -490,8 +490,9 @@ cont:
>  			 * Unlock and free up our temp pages.
>  			 */
>  			extent_clear_unlock_delalloc(inode, start, end, NULL,
> -						     EXTENT_DIRTY |
> -						     EXTENT_DELALLOC,
> +						     EXTENT_DELALLOC |
> +						     EXTENT_DO_ACCOUNTING |
> +						     EXTENT_DEFRAG,
>  						     PAGE_UNLOCK |
>  						     PAGE_CLEAR_DIRTY |
>  						     PAGE_SET_WRITEBACK |

I found we released the reserved space in cow_file_range_inline(), but at that time,
we didn't drop the outstanding_extents counter by the number of the delalloc extents,
so it might leave some reserved space which was not released. So I think we should remove
the release function in cow_file_range_inline().

(This bug is not introduced by your patch. but if we don't fix the above problem before
 applying your patch, the double release would happen because we have released the space
 in cow_file_range_inline())

> @@ -593,9 +594,10 @@ free_pages_out:
>  
>  cleanup_and_out:
>  	extent_clear_unlock_delalloc(inode, start, end, NULL,
> -				     EXTENT_DIRTY | EXTENT_DELALLOC,
> -				     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
> -				     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK);
> +				     EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING |
> +				     EXTENT_DEFRAG, PAGE_UNLOCK |
> +				     PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
> +				     PAGE_END_WRITEBACK);
>  	if (!trans || IS_ERR(trans))
>  		btrfs_error(root->fs_info, ret, "Failed to join transaction");
>  	else
> @@ -770,8 +772,8 @@ retry:
>  		extent_clear_unlock_delalloc(inode, async_extent->start,
>  				async_extent->start +
>  				async_extent->ram_size - 1,
> -				NULL, EXTENT_LOCKED | EXTENT_DELALLOC |
> -				EXTENT_DIRTY, PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
> +				NULL, EXTENT_LOCKED | EXTENT_DELALLOC,
> +				PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
>  				PAGE_SET_WRITEBACK);
>  		ret = btrfs_submit_compressed_write(inode,
>  				    async_extent->start,
> @@ -795,9 +797,9 @@ out_free:
>  				     async_extent->start +
>  				     async_extent->ram_size - 1,
>  				     NULL, EXTENT_LOCKED | EXTENT_DELALLOC |
> -				     EXTENT_DIRTY, PAGE_UNLOCK |
> -				     PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
> -				     PAGE_END_WRITEBACK);
> +				     EXTENT_DEFRAG | EXTENT_DO_ACCOUNTING,
> +				     PAGE_UNLOCK | PAGE_CLEAR_DIRTY |
> +				     PAGE_SET_WRITEBACK | PAGE_END_WRITEBACK);
>  	kfree(async_extent);
>  	goto again;
>  }
> @@ -884,7 +886,7 @@ static noinline int __cow_file_range(struct btrfs_trans_handle *trans,
>  		if (ret == 0) {
>  			extent_clear_unlock_delalloc(inode, start, end, NULL,
>  				     EXTENT_LOCKED | EXTENT_DELALLOC |
> -				     EXTENT_DIRTY, PAGE_UNLOCK |
> +				     EXTENT_DEFRAG, PAGE_UNLOCK |
>  				     PAGE_CLEAR_DIRTY | PAGE_SET_WRITEBACK |
>  				     PAGE_END_WRITEBACK);

If we remove the reserved space release function in cow_file_range_inline() as I said above,
we should add EXTENT_DO_ACCOUNTING here.

I will send a patch to fix the problem I said above soon, please wait a moment

The other code is OK.

Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>