Re: [PATCH] ext4: Fix ext4_bmap to flush the data to the disk with delalloc

[Eric Sandeen <sandeen@redhat.com>]

Aneesh Kumar K.V wrote:
> With delalloc we don't do block allocation in the write_begin/write_end.
> So when using bmap we first need to flush data to the disk so that blocks
> get allocated and then call generic_block_bmap.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  fs/ext4/inode.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 7035621..cfeb869 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1833,6 +1833,17 @@ sector_t ext4_bmap(struct address_space *mapping, sector_t block)
>  	journal_t *journal;
>  	int err;
>  
> +	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
> +			test_opt(inode->i_sb, DELALLOC)) {
> +		/*
> +		 * With delalloc we want to sync the file
> +		 * so that we can make sure we allocate
> +		 * blocks for file
> +		 */
> +		filemap_fdatawrite(mapping);
> +		filemap_fdatawait(mapping);
> +	}

This seems fine.

I wonder, does it make any sense at all to only do the flushing if the
block we wish to map is actually in a delalloc state at the moment?

-Eric

> +
>  	if (EXT4_I(inode)->i_state & EXT4_STATE_JDATA) {
>  		/*
>  		 * This is a REALLY heavyweight approach, but the use of